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University of Wollongong Thesis Collections
2012
The feasibility of eccentric cycling as a training
modality for increasing quadriceps strength at low
cardiovascular cost
Michael C. Lewis
University of Wollongong, [email protected]
Recommended Citation
Lewis, Michael C., The feasibility of eccentric cycling as a training modality for increasing quadriceps strength at low cardiovascular
cost, Masters by Research thesis, School of Health Sciences, University of Wollongong, 2012. http://ro.uow.edu.au/theses/3938
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THE FEASIBILITY OF ECCENTRIC CYCLING AS A
TRAINING MODALITY FOR INCREASING
QUADRICEPS STRENGTH AT LOW
CARDIOVASCULAR COST.
A thesis submitted in (partial) fulfilment of
the requirements of the award of the degree
MASTERS BY RESEARCH
from
UNIVERSITY OF WOLLONGONG
by
MICHAEL CARL LEWIS, B.Sc. (Exercise Science)
SCHOOL OF HEALTH SCIENCES
2012
1
CERTIFICATION
I, Michael C. Lewis, declare that this thesis, submitted in partial fulfilment of the
requirements for the award of Masters by Research, in the School of Health Sciences,
University of Wollongong, is wholly my own work unless otherwise referenced or
acknowledged. The document has not been submitted for qualifications at any other
academic institution.
__________________________________Date:________________________________
Michael Carl Lewis
Abstract
Eccentric, or lengthening, muscle contractions are a part of everyday life and are
involved in simple tasks such descending stairs. It is known that eccentric contractions
possess several unique attributes, but of particular interest to this study, a greater force
production capacity coupled with a decreased metabolic demand.
These attributes
suggest that eccentric exercise is well suited for the clinical rehabilitation setting. The
ability to produce equivalent muscular force for a lower metabolic requirement will
potentially allow individuals with low exercise tolerance to maintain or build muscular
strength, where previously this was difficult to achieve due to central limitations.
Eccentric aerobic exercise can be performed on a modified cycle ergometer and requires
eccentric contractions to resist the force of the pedal cranks, generated by an engine.
Several studies have demonstrated that during eccentric cycling the metabolic oxygen
requirement and heart rate is significantly lower than concentric cycling at equal loads.
It is also known that when workloads are matched based on metabolic or cardiovascular
workloads, eccentric cycling can be performed at much higher workloads, up to 450W.
This type of high force eccentric cycle training has been shown to increase isometric
strength in healthy individuals, the elderly, and in individuals with pathologies such as
chronic obstructive pulmonary disease, cancer and congestive heart failure.
The
benefits of high force eccentric cycling have been established. However, there have
been no studies at low absolute workloads to determine whether skeletal muscle
remodelling will produce similar increases in strength. Single joint studies in humans
have demonstrated that muscle damage following eccentric contractions is volume
dependant and influenced less by intensity, supporting the idea that the high number of
eccentric contractions performed during eccentric cycling may produce enough muscle
damage to induce remodelling and result in an increase in strength. It is the aim of this
project to determine whether low force eccentric cycling can be utilised as a training
modality to improve strength at low cardiovascular workloads
Study 1 determined the acute physiological response to low load eccentric cycling
during a single exercise session. Twelve healthy subjects, six male and six female
university students, (21 ± 2 years, BMI 23.8 ± 4.1) performed 30 minutes of concentric
and eccentric cycling at 60% of peak aerobic power output. The results showed that for
i
an equivalent absolute power output, oxygen consumption and heart rate were
significantly lower during eccentric compared with concentric cycling despite equal
absolute power output and muscle activation. Study 2 was then performed to determine
the adaptations of an 8 week training program at 60% of peak concentric workload.
Seventeen sedentary males (43 ± 8 years, BMI 28.6 ± 5.2, VO2 peak 30.5 ± 5.8
ml.kg.min-1) completed an 8-week concentric (Con, n=8) or eccentric (Ecc, n=9)
training program.
Subjects were matched for baseline peak isometric quadriceps
strength. In addition, a 6 repetition max protocol on a 45o leg press was performed as a
measure of functional strength. Training workloads were set at 60% of individual peak
concentric workload and heart rate, as well as ratings of perceived exertion (RPE), were
continuously recorded during sessions. Isometric strength was tested at weeks 3, 5, 7
and one week post-training, along with functional strength. During the 8 weeks of
training, both groups achieved the prescribed 180 W workload, with the mean power
achieved by the Ecc group within 5% of the target. Lower cardiovascular work in
eccentric cycling was confirmed (Con = 154 beats∙min-1, Ecc 95 = beats∙min-1), with
lower ratings of perceived exertion (Con = 14.9, Ecc = 9.5). There was no difference in
isometric or functional strength between the groups at baseline. Following training, both
Con and Ecc groups significantly improved isometric and functional strength. The Con
group improved isometric and functional strength by 14.7% and 12.7% and the Ecc
group by 12.7% and 10.7% respectively.
The current investigation has demonstrated that when a 30 minute training session of
eccentric cycling is performed, power output equivalent to concentric cycling can be
performed with lower cardiovascular and metabolic stress. When utilised as a training
modality in sedentary males, low load eccentric cycling can achieve isometric and
functional strength gains. This was achieved with a 38% lower heart rate and 36% lower
RPE compared to concentric cycle training. The implications are that even at low loads,
strength adaptations are possible which highlights the usefulness of eccentric aerobic
exercise as a training modality to improve muscular strength and maintain activities of
daily living in individuals with exercise intolerance.
ii
Acknowledgments
I would like to thank the following people who have helped me throughout the
wonderful experience that was my masters:
•
Mr Marc Brown and Dr Greg Peoples for their ongoing excellent supervision
throughout my research degree. They have provided outstanding support
and guidance significantly enhanced my development in this field.
•
My secondary supervisors, Dr Herb Groeller and Dr John Sampson for their
support and advice throughout my research degree.
•
Jo Odgers, Anne van den Heuval, Sean Notley, Dan Lee, Laura Holland, Brooke
Collier, for their assistance in learning the laboratory skills required to complete
this research and for their assistance throughout the data collection periods.
•
The subjects who willingly gave up their time to participate in this project.
Without their time and effort this project could not have been performed.
•
Finally, I would like to thank my friends and family for their support throughout
my research.
iii
Table of Contents
Abstract .............................................................................................................................. i
Acknowledgments ............................................................................................................iii
Table of Contents ............................................................................................................. iv
List of Figures ................................................................................................................viii
List of Tables..................................................................................................................... x
Chapter 1: Introduction ..................................................................................................... 1
1.1 Sarcopenia ............................................................................................................... 1
1.2 Exercise Intolerance ................................................................................................ 2
1.3 Resistance Training ................................................................................................. 2
1.4 Eccentric Work........................................................................................................ 4
1.5 Eccentric cycle ergometry ....................................................................................... 7
1.5.3 Eccentric cycling training studies ...................................................................... 16
1.6 Concluding comments........................................................................................... 24
1.7Aims and Hypothesis ............................................................................................. 25
Chapter 2: Acute physiological response to 30 minutes of eccentric cycling. ............... 27
2.1 Introduction ........................................................................................................... 27
2.2 Methods ................................................................................................................. 29
2.2.1 Equipment .......................................................................................................... 29
2.2.1.1 Custom built cycle ergometer ..................................................................... 29
2.2.1.2 Eccentric Mode ........................................................................................... 29
2.2.1.3 Concentric Mode ......................................................................................... 29
2.2.2 Subjects .............................................................................................................. 31
2.2.3 Experimental Standardisation ............................................................................ 31
2.2.4 Experimental design ........................................................................................... 31
2.2.5 Peak workload test ............................................................................................. 33
2.2.6 Familiarisation ................................................................................................... 33
iv
2.2.7 Thirty minute submaximal test protocols........................................................... 33
2.2.8 Measurements .................................................................................................... 35
2.2.8.1 Power, Cadence and Heart Rate .................................................................. 35
2.2.8.2 Muscle Soreness .......................................................................................... 35
2.2.8.3 Metabolism.................................................................................................. 36
2.2.8.4 Electromyography ....................................................................................... 36
2.2.9 Statistical Analysis ............................................................................................. 37
2.3 Study One Results ................................................................................................. 38
2.3.1 Subject characteristics ........................................................................................ 38
2.3.2. Eccentric work performed during familiarisation ............................................. 40
2.3.3 Variability of work during familiarisation ......................................................... 40
2.3.4 Muscle Soreness ................................................................................................. 43
2.3.5 Using muscle soreness as an indicator of familiarisation .................................. 45
2.3.6 Oxygen Consumption ........................................................................................ 47
2.3.7 Heart rate ............................................................................................................ 50
2.3.8 Muscle Activation .............................................................................................. 53
2.4 Discussion ............................................................................................................. 55
2.4.1 Concluding Comments ....................................................................................... 60
Chapter 3: Training Study ............................................................................................... 62
3.1 Introduction ........................................................................................................... 62
3.2 Methods ................................................................................................................. 64
3.2.1 Equipment .......................................................................................................... 64
3.2.2 Subjects .............................................................................................................. 65
3.2.3 Experimental Standardisation ............................................................................ 65
3.2.4 Experimental Design .......................................................................................... 66
3.2.5 Baseline Data ..................................................................................................... 68
3.2.5.1 Anthropometric Data....................................................................................... 68
v
3.2.5.2 Resting Data .................................................................................................... 68
3.2.6 Peak Workload Test ........................................................................................... 69
3.2.6.1 Measurements during peak workload test ....................................................... 69
3.2.7 Isometric Strength .............................................................................................. 71
3.2.8 Electromyography (EMG) ................................................................................. 72
3.2.9 Functional Strength ............................................................................................ 72
3.2.10 Familiarisation ................................................................................................. 73
3.2.10.1 Measurements during familiarisation............................................................ 73
3.2.11 Training Intervention ....................................................................................... 73
3.2.12 Training Impulse (TRIMP) .............................................................................. 74
3.2.13 Final Testing .................................................................................................... 75
3.2.14 Statistical Analysis ........................................................................................... 75
3.3 Results ................................................................................................................... 76
3.3.2 Physical Characteristics ..................................................................................... 76
3.3.3 Resting cardiovascular measurements. .............................................................. 79
3.3.4 Indices of autonomic activity ............................................................................. 82
3.3.5 Peak Aerobic Cycle Test .................................................................................... 84
3.3.6 Familiarisation ................................................................................................... 87
3.3.6.1 Power output ................................................................................................... 87
3.3.6.2 Variability of power output ............................................................................. 87
3.3.6.3 Muscle Soreness .............................................................................................. 90
3.3.6.4 Using muscle soreness as an indicator of familiarisation ............................... 92
3.3.7 Training Session Data ........................................................................................ 94
3.3.7.1 Work performed .............................................................................................. 94
3.3.7.2 Training heart rates ......................................................................................... 95
3.3.7.3 Training ratings of perceived exertion ............................................................ 95
3.3.8 Maximal voluntary contraction ........................................................................ 100
vi
3.3.8.1 Peak Torque .................................................................................................. 100
3.3.8.2 Muscle activation .......................................................................................... 103
3.3.9 Functional Strength .......................................................................................... 105
3.4 Discussion ........................................................................................................... 107
3.4.1 Strength adaptations to low load eccentric cycling .......................................... 108
3.4.2 Cardiovascular adaptations to eccentric exercise ............................................. 113
Chapter 4: Clinical Implications ................................................................................... 118
4.1 Limitations .......................................................................................................... 123
4.2 Conclusion .......................................................................................................... 124
References ..................................................................................................................... 125
vii
List of Figures
Figure 1.1: The progression of eccentric cycle ergometry. ............................................ 10
Figure 2.1 (A) The custom built eccentric ergometer ..................................................... 30
Figure 2.2: Study one experimental design ..................................................................... 32
Figure 2.3 Thirty minute session design showing data collection periods. .................... 34
Figure 2.4. Visual AnalougueScale (VAS) ..................................................................... 35
Figure 2.5: Photographs of surface electromyography electrode placement. ................. 37
Figure 2.6: Eccentric power output during familiarisation sessions. .............................. 41
Figure 2.7: Muscle soreness following familiarisation sessions. ................................... 43
Figure 2.8: A lack of linearity between (A) % of target power output (B) power output
variability and muscle soreness....................................................................................... 46
Figure 2.9: Oxygen consumption throughout a 30 minute bout of concentric  or
eccentric  cycling at 60% of peak concentric workloads. ............................................ 48
Figure 2.10: Heart rate throughout a 30 minute bout of concentric  or eccentric 
cycling at 60% of peak concentric workloads................................................................. 51
Figure 2.11: Total quadriceps muscle activity measured by electromyography. ............ 53
Figure 3.1: Concentric recumbent cycle ergometer ........................................................ 64
Figure 3.2: Study design ................................................................................................. 67
Figure 3.3: The BORG category scale ............................................................................ 70
Figure 3.4: Isometric strength testing apparatus ............................................................. 71
Figure 3.5: 45 degree leg press ....................................................................................... 73
Figure 3.6: Resting cardiovascular parameters ............................................................... 80
Figure 3.7: Peak aerobic (A) workload, (B) O2 consumption and (C) heart rate for
concentric  (n=8) and eccentric  (n=9) training groups ............................................. 85
Figure 3.8: Eccentric power output during familiarisation session................................ 88
Figure 3.9: Muscle soreness following familiarisation sessions ..................................... 90
Figure 3.10: The lack of linearity between (A) mean power output, (B) power output
variability andmuscle soreness ........................................................................................ 93
viii
Figure 3.11: Mean power output during eccentric training sessions .............................. 94
Figure 3.12: Mean heart rate data over the 16 training sessions for the concentric 
(n=8) and eccentric  (n=9) training groups.. ................................................................ 96
Figure 3.13: Mean ratings of perceived exertion data over the 16 training sessions for
the concentric  (n=8) and eccentric  (n=9) training groups. ...................................... 97
Figure 3.14: Peak isometric torque values over the 5 testing sessionsfor concentric 
(n=8) and eccentric  (n=9) training groups. ............................................................... 101
Figure 3.15: Peak quadriceps activation ...................................................................... 103
Figure 3.16: Peak functional strength of the lower limb extensors for concentric  (n=8)
and eccentric  (n=9) training groups .......................................................................... 105
ix
List of Tables
Table 1.1: Single bout eccentric cycling literature.......................................................... 15
Table 1.2 Chronic eccentric cycling studies ................................................................... 23
Table 2.1: Subject characteristics ................................................................................... 39
Table 2.2: Familiarisation summary ............................................................................... 42
Table 2.3: Muscle soreness during familiarisation ......................................................... 44
Table 2.4: Oxygen consumption during a single 30 minute bout of equivalent load
concentric or eccentric cycling........................................................................................ 49
Table 2.5: Heart rate during a single 30 minute bout of equivalent load concentric or
eccentric cycling.............................................................................................................. 52
Table 2.6:
Muscle activation during a single 30 minute bout of equivalent load
concentric or eccentric cycling........................................................................................ 54
Table 3.1: Training Session Timeline ............................................................................. 74
Table 3.2: Physical characteristics .................................................................................. 77
Table 3.3: Anthropometric measurements ...................................................................... 78
Table 3.4: Resting cardiovascular measurements ........................................................... 81
Table 3.5: Heart rate variability ..................................................................................... 83
Table 3.6: Peak aerobic cycle test data ........................................................................... 86
Table: 3.7: Work performed and variability of work during familiarisation ................ 89
Table 3.8: Muscle soreness after familiarisation sessions .............................................. 91
Table 3.9: Training session data ..................................................................................... 98
Table 3.10: Training Impulse (TRIMP) ......................................................................... 99
Table 3.11 Individual peak Torque (N.m-1) .................................................................. 102
Table 3.12 Muscle activation ........................................................................................ 104
Table 3.13: Functional strength.................................................................................... 106
x
Chapter 1: Introduction
1.1 Sarcopenia
Sarcopenia, the loss of skeletal muscle mass, has been well documented as part of the
natural aging process (Evans, 1995). The term sarcopenia was first used by Rosenberg
(1989), and the literal breakdown of the word means “loss of flesh” (Peterson, 2010).
Although in its original context, the term sarcopenia referred purely to a decrease in
muscle mass, it is now often used to encompass a decrease in skeletal muscle function,
caused from other factors such as reductions in central and peripheral nervous system
activity (Doherty et al., 2003). A recent working group into sarcopenia proposed the
consensus definition that “Sarcopenia is the age associated loss of skeletal muscle mass
and function” (Chumlea et al., 2011). Although low muscle mass has been shown to
have negative implications on health and mortality (Newman et al., 2006), it has been
demonstrated that muscular strength is a much stronger predictor of health than muscle
mass alone (Newman et al., 2006).
Muscular strength has implications on an
individual’s functional status (Warburton et al., 2001a), the ability to perform activities
of daily life and affects an individual’s overall quality of life (Warburton et al., 2001b).
Decreased muscular strength can be the limiting factor which decides an individual’s
level of independence (Janssen et al., 2002). Common tasks such as rising from a chair,
ascending/descending stairs and simply walking are affected if muscular strength is low
(Ploutz-Snyder et al., 2002). Not only is the ability to perform these tasks important for
an individual’s quality of life, but the performance of simple tasks such as the
achievable speed of an individual’s gait is related to life expectancy (Studenski et al.,
2011). Although pharmacological and hormone replacement interventions have been
successfully applied to increase muscle mass, resistance training is the most effective
way of increasing muscle mass and strength in individuals with sarcopenia (Borst,
2004). Reductions in muscular strength not only effect the elderly (Ferrucci et al.,
1997), but are also common amongst individuals with pathologies such as Chronic
Obstructive Pulmonary Disease (COPD) (Skumlien et al., 2006) and Chronic Heart
Failure (CHF) (Esposito et al., 2010). Similar to the benefits of strength training
observed in the elderly, it has been shown that individuals with COPD and CHF reap
similar benefits by increasing muscular strength (Pyka et al., 1994).
1
These two
pathology groups have been used as examples of conditions associated with low
exercise tolerance (O’Donnell et al., 2001; Mancini et al., 1992).
1.2 Exercise Intolerance
This thesis is not focused on CHF and COPD specifically, but uses these pathological
groups as specific examples that suffer exercise intolerance. CHF is characterised by
the inability of the heart to maintain normal cardiac output (Ryan et al., 2011) and
results in a decreased delivery of oxygen to working muscles during exercise (Esposito,
et al., 2010). COPD patients also suffer a reduced capacity to supply muscles with
oxygen however in COPD it is a result of a pulmonary airflow limitation (Viegi et al.,
2007) rather than cardiac output.
This centrally limited oxygen supply in both
conditions results in low exercise tolerance and symptomatic reporting of dyspnoea and
fatigue (Zeng & Jiang, 2012).As a result both COPD and CHF are associated with
decreased maximal exercise capacity (Drexler et al., 1992; Esposito, et al., 2010) which
reduces the ability of sufferers to participate in physical activity. For many years the
exercise intensity achieved by individuals with COPD (Gosselink et al., 1997) was
believed to be too low to produce peripheral muscle adaptations. This belief that
exercise intolerance would prevent individuals from exercising at intensities high
enough to induce strength improvements (Hanson, 1994) has since been disproven in
both COPD (Arizono et al., 2011) and CHF (Jankowska et al., 2008) patients. Due to
the degenerative nature of COPD and CHF it is unlikely that these two groups will be
able to improve their aerobic capacity centrally, however there is evidence of modest
improvements in exercise tolerance through peripheral adaptations by increasing
muscular strength (Belardinelli et al., 1995; Clark et al., 1996). Due to the potential
health and well being benefits of increasing muscular strength, particularly in
functionally limited individuals, it is important to find the most effective method for
developing muscular strength, which is achievable for individuals with low exercise
tolerance.
1.3 Resistance Training
Traditional resistance training has been shown to increase strength in healthy adults, the
elderly, individuals with COPD and CHF. It is generally in the form of free weights or
machine weights (Cotterman et al., 2005) but can be any form of external load such as
2
resistance bands (Findley, 2004), sand filled bags or exercise using body weight as
resistance (LaChance & Hortobagyi, 1994). Known adaptations of resistance training
that result in an increase in muscular strength are increasing activation of the agonist
muscle or muscles (Sale, 1988), improving the synchronicity of neural signals (Semmler
& Nordstrom, 1998), increasing muscle fibre cross sectional area (Shoepe et al., 2003)
and altering intrinsic architectural characteristics such as muscle fibre length (Seynnes
et al., 2007) and muscle fibre pennation angle (Kawakami et al., 1993).
These
adaptations result in an increase in the force that can be produced by a muscle or group
of muscles (Kraemer et al., 2002). The cost of resistance exercise on the cardiovascular
system is an acute increase in heart rate and blood pressure (Wise & Patrick, 2011).
Heavy weight lifting results in an increase in heart rate, a mechanical compression of
blood vessels combined with a pressor effect and valsalva response that elevates
systolic and diastolic blood pressure to extreme levels (MacDougall et al., 1985). The
increase in heart rate and blood pressure results in both a pressure and volume overload
on the heart (Williams et al., 2007).
Traditional resistance training programmes involve the repetitive lifting and lowering of
a mass against gravity.
This involves two specifically separate types of muscle
contraction. The lifting phase is achieved by performing a concentric contraction where
the muscle produces force as it is shortening, where eccentric contractions are utilised
during the lowering phase and involve the muscle producing force whilst lengthening
(Kraemer et al., 2002).
Both concentric and eccentric muscle contractions are
performing external work as defined by the product of force and displacement. The
work done on an object can be measured in both, positive (production of force) and
negative (absorption of force) directions. Positive work has been defined as the product
of the force exerted by a muscle and the distance it has shortened where negative work
is the product of the force absorbed by the muscle, and the distance it has lengthened
(Abbott et al., 1952). More than often, when referring to muscle contractions, these
definitions of work have been termed concentric (positive) and eccentric (negative)
work (Cleak & Eston, 1992). To remain consistent with the current literature in this
area, the terms concentric and eccentric work will be used from this point onwards.
This thesis will focus on the particular benefits of eccentric contractions.
3
1.4 Eccentric Work
Eccentric work is an essential part of our daily activities (Dickinson et al., 2000;
Lindstedt et al., 2001) and is characterised by a low metabolic demand for a high power
output (LaStayo et al., 2000). Human locomotion is a good example where uphill
walking is primarily concentric work, and downhill walking is predominantly eccentric
work and level walking is a combination of both (Pimental et al., 1982). There are
several unique attributes associated with eccentric exercise including (i) reduced
metabolic demand, (ii) increased contractile force production, (iii) increased muscle
damage, (iv) increased muscle soreness and (v) unique neuromuscular activation
strategies.
1.4.1 Reduced Metabolic Demand
High eccentric forces elicit lower metabolic costs than equivalent concentric forces
(Abbott et al., 1952). Animal studies have shown that for a given stimulus, oxygen
consumption is lower if the force is great enough to create an active lengthening of the
muscle, when compared to isometric or concentric contractions (Stainsby, 1976).
Rodent studies demonstrate that downhill treadmill running requires significantly lower
oxygen consumption, when compared to level or incline running (Armstrong, Laughlin,
et al., 1983; Armstrong, Ogilvie, et al., 1983). This lower oxygen consumption has also
been demonstrated in human subjects, engaging in downhill treadmill running, when
compared to uphill or level treadmill running (Minetti, et al., 2002). This lower oxygen
consumption leads to decreased heart rate, blood pressure and cardiac index responses
during eccentric versus concentric leg squats at equal absolute loads (Vallejo et al.,
2006).
1.4.2 Increased contractile force
Eccentric muscle activation is associated with greater contractile force production than
concentric and isometric activation (Doss & Karpovich, 1965; Katz, 1939). Early work
in animals (Fenn & Marsh, 1935; Katz, 1939) clearly shows that when the speed of a
muscle shortening increases, the force of the contraction decreases. This force velocity
relationship is also present in human muscle (Wilkie, 1950). In addition, when the
velocity becomes negative and the muscle is actively lengthened, the force increases
further (Katz, 1939). It has also been demonstrated that after 3 months of resistance
4
training followed by 3 months of detraining, concentric strength and cross-sectional
area returned to pre-training levels where eccentric strength is maintained (Andersen et
al., 2005). This indicates that eccentric force production will be maintained for longer
after training interventions. Similarly it has been shown that eccentric strength is
maintained to a greater extent than concentric and isometric strength during aging
(Poulin et al., 1992).
1.4.3 Muscle Damage and Muscle Soreness
Eccentric muscle activation is associated with greater muscle soreness, swelling,
stiffness and acute strength losses (Cleak & Eston, 1992). Muscle soreness from high
force eccentric exercise presents within 24hours post-exercise and peaks around 2-3
days (Clarkson et al., 1992). It has been shown that mechanical actomyosin detachment
occurs during high force eccentric contractions rather than the ATP dependant
detachment seen in concentric contractions (Flitney & Hirst, 1978). This “forced”
detachment causes high strain on the elements of the muscle fibre and could explain the
increased tissue damage associated with high force eccentric contractions (Enoka,
1996). There are two signs of muscle damage that are generally accepted after a series
of eccentric contractions, these are disruption of sarcomeres within myofibrils or
damage to the excitation-contraction system process (Proske & Morgan, 2001). Rat
studies involving downhill exercise have shown that there is significantly more A-band
lesions in the downhill running group than in the level running or control groups
(Robert et al., 1988). It has also been shown in both animal (Armstrong, et al., 1983)
and human (Ronald et al., 1989) studies that creatine kinase, the standard marker of
muscle damage (Ebbeling and Clarkson, 1989), is elevated after eccentric exercise. If
this enzyme is present in blood, it indicates that there is damage to the muscle
membrane or changes to its permeability, as under normal conditions it cannot leak
from the myocyte (Lee et al., 2002).
Longer duration studies using lower force
eccentric contractions have also reported higher initial muscle soreness than concentric
contractions of equal force. It has additionally been demonstrated that muscle damage
produced by eccentric contractions is independent of intensity (Paschalis et al., 2005).
Equal volumes of high and low intensity eccentric contractions produce similar amounts
of muscle damage particularly in the initial sessions (Vallejo et al., 2006).
5
1.4.4 Activation strategies
The widely accepted size principle (Cope & Pinter, 1995; Henneman & Olson, 1965;
Henneman et al., 1965) proposes that an orderly recruitment pattern exists with muscle
activation. However, it appears that eccentric contractions have a unique activation
strategy that does not follow this principle (Enoka, 1996). Submaximal eccentric
contractions utilise preferential recruitment of high threshold (fast twitch) fibres, which
is simultaneously accompanied by a derecruitment of low threshold (slow twitch) fibres
(Nardone et al., 1989). This is not entirely accepted with a recent review by Duchateau
and Enoka (2008) suggesting that although there is a different activation strategy during
eccentric contractions, they believe it is not due to preferential recruitment of fast twitch
fibres (Duchateau and Enoka, 2008). It has also been shown that eccentric contractions
and slow concentric contractions elicit lower neuromuscular activation than fast
concentric contractions (Aagaard et al., 2000). For example, Rectus Femoris activation
is significantly higher in heavy concentric cycling than heavy eccentric cycling (Perrey
et al., 2001). It was also noted that heavy eccentric cycling produced lower activation
than moderate load concentric cycling.
Maximal activation during eccentric
contractions is lower than concentric cycling and could be a protective mechanism to
limit too great a force production during eccentric contractions (Aagard et al., 2000).
1.4.5 Eccentrically biased resistance training
It has been demonstrated that specific eccentric resistance training is a potent stimulus
for producing muscle hypertrophy and strength (Higbie et al., 1996). When concentric
and eccentric muscle contractions are isolated and performed individually, eccentric
contractions produce greater increases in muscular strength than concentric contractions
(Farthing & Chilibeck, 2003; Roig et al., 2009). A greater ability to produce force
using eccentric muscle contractions allows individuals to train at workloads
supramaximal to peak concentric loads and results in greater improvements in strength
(Hortobágyi & DeVita, 2000). A meta-analysis and systematic review of 20 studies
revealed eccentric training is a superior method for improving total strength and
suggests that it appears to be a more potent stimulus for producing hypertrophy (Roig,
et al., 2009).
6
1.4.6 Various modes of eccentrically biased exercise
A common method for applying an eccentric stimulus during resistance training is to
increase the mass to supramaximal concentric loads (Keogh et al., 1999).
The
advantage of this type of eccentric training is that it allows for the generation of higher
forces than can be achieved concentrically however, it does require the assistance of a
spotter or a specifically designed piece of equipment. Another method of providing an
eccentric stimulus using traditional resistance training is to accentuate the eccentric
phase by performing eccentric contractions followed by an assisted passive return to the
start position avoiding concentric contractions (Lorenz, 2010).
Athletes frequently
utilise exercise using the stretch shortening cycle in which a fast eccentric contraction is
performed, immediately followed by a maximal concentric contraction.
This fast
eccentric contraction stores elastic energy to be utilised in the proceeding concentric
contraction to maximise force production. Apart from these common techniques it is
also possible to perform longer duration eccentric exercise that is a combination of
eccentric contraction used in resistance training and aerobic exercise. This includes
running or walking downhill, downhill treadmills and specifically to this project,
modified cycle ergometers to allow eccentric activation (Cleak & Eston, 1992; Yu et al.,
2002). This gives the potential of achieving benefits of both strength and aerobic
exercise.
1.5 Eccentric cycle ergometry
Eccentric cycling is not a new concept with the first published studies using eccentric
cycling dating back to the early 1950’s (Abbott et al., 1952; Asmussen, 1952). The
eccentric cycle ergometer used by Abbot et al. (1952) can be seen in Figure 1.1A and
utilised two standard bicycles coupled in opposition. This allowed one subject to pedal
conventionally using concentric contractions and a second subject to resist using
eccentric contractions. Asmussen (1952) used a different approach and devised an
altered gearing system on a bicycle and it was ridden on a downhill treadmill. An
additional cog resulted in the pedals turning backwards therefore the matching the
movement patterns of conventional concentric cycling. However, this method was not
desirable as it required considerable skill from the rider. The first motorised ergometer
(Figure 1.1B) appeared in the literature in in 1953 and utilised a 2.5 horse power electric
motor that could resist the greatest torque produced by the subjects (Abbott & Bigland,
7
1953). Bonde-Petersen (1969) went one step further and developed a system using a 6
horse power electric motor, with an induction clutch and a magnetically braked
ergometer. This allowed for better control of known workloads from the motor to the
ergometer.
The workloads could be calibrated using the magnetically braked
ergometer. With this ergometer, workloads are adjusted via the brake and subjects
control the pedalling cadence in time with a metronome. This design was further
advanced several years later which allowed the pedal frequency to be determined by the
engine and subjects adjust the load by producing more or less effort against the pedals
(Bigland-Ritchie et al., 1973). From this point onward in the literature any studies that
have used eccentric cycling protocols have used motorised eccentric cycle ergometers
of similar design. A modern eccentric ergometer (LaStayo et al, 2003) can be seen in
Figure 1.1C.
This literature review will be split into two separate sections. The first section (1.5.1)
will review current practices regarding familiarisation of subjects who will perform
eccentric cycling.
The second section (1.5.2) will review the acute physiological
response to a single bout of eccentric cycling.
This single bout section will also
describe the evolution of the eccentric ergometer design from inception through to its
current form. Finally, the third section (1.5.3) will review the literature associated with
chronic eccentric cycling programs utilised as a training tool.
1.5.1 Familiarisation
It is a common practice in the eccentric cycling literature to provide subjects with a
familiarisation period to become accustomed to the unusual technique involved in
eccentric cycling. Previous papers have reported that as little as a single familiarisation
session is sufficient to remove any muscle soreness (Dufour et al., 2004), however 3-4
familiarisation sessions are generally used to ensure that the muscle soreness response is
minimal and to acquire the specific coordination of eccentric cycling (Dufour et al.,
2007; Perrey et al., 2001).
Although these studies have addressed the need for a familiarisation period there has
been no data published on the average workload or variation in workload over these
8
initial sessions. The SRM power crank system will allow this study to collect second by
second power data to determine how accurately the target workload is being achieved
and the variability of the work. This will give a greater understanding of how many
sessions are required to be confident that an eccentric workload is being accurately
achieved.
9
A.
B.
C.
Figure 1.1: The progression of eccentric cycle ergometry. (A) The first eccentric cycle
ergometer (Abbott et al., 1952). (B) The first motorised eccentric cycle ergometer (Abbott and
Bigland, 1953). (C) A modern eccentric cycle ergometer with biofeedback system (LaStayo et
al., 2003)
10
1.5.2 The acute effect of a single bout of eccentric cycle ergometry
This section of the literature review will chronologically step through single bout
eccentric cycle ergometry studies. A summary of the single bout eccentric cycling
literature can be seen in Table 1.1. Using the coupled bicycle ergometer discussed in
section 1.4, Abbott et al. (1952) were able to demonstrate that oxygen consumption was
significantly greater during concentric compared to eccentric cycle ergometry of equal
force production. The concentric oxygen consumption was 2.4 times greater at 25
revs.min-1 and increased with increasing pedal frequency to the highest difference of 5.2
times at 52 revs.min-1. Unfortunately this study only had two subjects, and although
producing significant differences was not as scientifically rigorous as it could have
been. It was however important findings and the foundation that many future studies
were based from. In the same year Asmussen (1952) found similar results using the
downhill treadmill cycling protocol.
It was found that at 45 revolutions.minute-1,
concentric cycling cost 5.9 more oxygen than eccentric and this increased to 125 times
greater at 102 revs.min-1. Similar to Abbott et al. (1952), Asmussen hypothesised that
the reduced oxygen consumption was due to a lesser number of active fibres active
during eccentric contractions. Abbott and Bigland (1953) confirmed the earlier results
of a lower oxygen cost during eccentric cycle ergometry compared to equal force
concentric cycle ergometry and similarly to Asmussen (1952) attributed the difference
to lesser active muscle fibres. The three early studies portrayed the common findings
of, lower oxygen consumption during eccentric cycling than concentric cycling of
equivalent work, an increase in the relative difference in oxygen consumption at greater
pedal frequencies, and finally they all shared the hypothesis that the difference between
concentric and eccentric oxygen consumption increased with increasing cadence
(Abbott et al., 1952; Asmussen, 1952; Abbott et al., 1953).
Bigland-Ritchie and Woods et al. (1976) used more advanced technologies over 20
years later and confirmed that oxygen consumption is lower during eccentric cycling at
equal workloads and the ratio is greater with increasing pedal frequencies. In order to
test the hypothesis that this difference was due to less active muscle fibres, surface
electromyography of the quadriceps was collected.
The results demonstrated that
muscle activation was greater in concentric compared to eccentric cycling ranging from
1.5 to 3 times at 30 and 100 revs.min-1respectively. This confirms the hypothesis that
11
oxygen consumption differences were partly due to lower active muscle fibres (Abbott
et al., 1952; Asmussen, 1952; Abbott et al., 1953), however it is not the sole
contributing factor. Muscle activation of the quadriceps was measured as it is the
largest contributor to force production during cycling. The assumption was made that
the metabolic differences are similar in other working muscles. It was discussed that
with increasing force produced by the quadriceps at higher workloads that core
stabilising muscles would be required to work more. However during cycle ergometry
core stabilisers are performing isometric contractions and the oxygen consumption
should be similar between concentric and eccentric cycling. Another possibility was
due to the increased oxygen consumption in concentric cycling, as cardiac and
respiratory muscle metabolism would need to increase. However, based off calculations
this could only attribute to 5% of the total oxygen consumption. This provides insight
that when oxygen consumption is normalised to muscle fibre activity, the oxygen
consumption is still lower during eccentric contractions.
Perrey et al. (2001) conducted a study comparing the oxygen uptake kinetics between
eccentric and concentric cycle ergometry.
The research model for this study
incorporated three important groups. A high force concentric group (330W), a high
force eccentric group (330W) that was matched to the workload of the high force
eccentric group, and a low force concentric group (70W) matched to equal metabolic
cost with the high eccentric group. The results clearly showed that when equal absolute
workloads of 330W are performed, eccentric cycling elicits significantly lower heart
rate, oxygen consumption and muscle activation. Further, when relative metabolic
workloads are equal, eccentric cycling can be performed at greater than four times the
external workload. In addition to the work of Bigland and Ritchie (1976), this study
found that not only was the total activation lower, but there was no change in activity
over time as was seen in the concentric condition. Interestingly, when metabolic work
was matched, significantly higher heart rates were demonstrated in the eccentric group.
This was attributed to higher activation of mechano-receptors in the eccentric group due
to greater muscle tension.
Walsh et al. (2001) used a high force eccentric cycling model to investigate the effects
of eccentric exercise on oxidative metabolism. As discussed in section 1.4.3, it is
12
known that eccentric contractions are associated with muscle damage and soreness.
This study found that 30 minutes of high force eccentric cycling did produce muscle
soreness but did not produce a significant change in the blood marker creatine kinase. It
was concluded that although eccentric cycling produces muscle soreness, it does not
have negative effects on oxidative function at the prescribed workloads.
Dufour et al. (2004) conducted a study whereby subjects performed an incremental
exercise protocol, using concentric activation until exhaustion. These workloads were
then matched in the eccentric mode to compare circulatory responses. It was clearly
demonstrated that for the same absolute workload at any point throughout the
incremental protocol, that there was lower oxygen consumption and heart rate during
eccentric cycling when compared to concentric cycling.
Dufour et al. (2006) used a similar model with a high force concentric group (270W)
matched with a high force eccentric group (270W), and a low force concentric group
(70W) matched to the high force eccentric group for metabolic cost. Similar to the
results by Perrey et al. (2001), this study found that when concentric and eccentric
cycling was performed at an equivalent 270W the oxygen consumption, heart rate and
muscle activation was significantly lower in the eccentric group. Confirming the results
by Perrey et al. (2001) the results demonstrate that heart rate is significantly greater
during eccentric cycling despite an equal metabolic cost of 1.17 L.min-1 and 1.14 L.min1
for the eccentric and concentric groups respectively. It was determined that metabolic
cost was the primary factor responsible for the cardiac output response accounting for
74%, however 26% was found to be due to mechanical tension.
A study by Elmer et al, (2010) determined the joint contributions to the absorption of
force during eccentric cycling to be 10% ankle, 58% knee, 29% hip with the remaining
3% of absorbed force being taken above the hip.
This has validated the use of
quadriceps as the muscle of choice by Bigland-Ritchie and Woods et al. (1976), Perrey
et al. (2001) and Dufour et al. (2006) when measuring electromyography as it is the
muscle group that is performing the majority of work.
13
The studies outlined above have been the primary investigations determining the
physiological response to a single bout of eccentric cycling with particular focus on the
metabolic, cardiovascular and neuromuscular response. This is not an exhaustive list of
every published study that has utilised an eccentric cycling model, however the above
studies have particular relevance to this project. For example, some studies that have
not been included have utilised eccentric cycling protocols as a model to induce muscle
damage and look at the effects of a prostaglandin-inhibiting drug and its effect on
muscle soreness (Kuipers et al., 1985). Studies such as this have been left out of this
literature review as they are not relevant despite using an eccentric cycle ergometry
model. Section 1.5.3 will review the studies that have investigated the chronic effect of
eccentric cycle ergometry when it is performed as a training program.
1.5.2.1 Single bout eccentric cycling summary
The general consensus from single bout eccentric cycling literature is that when
eccentric and concentric cycling is matched for equivalent oxygen consumption,
eccentric cycling can produce far greater force than concentric cycling (Perret et al.,
2001; Dufour et al., 2004; Dufour et al., 2006). It is also clear that when eccentric and
concentric cycling are matched, producing the same external force, that oxygen
consumption, heart rate and muscle activation is significantly lower during eccentric
cycling (Bigland-Ritchie et al., 1973; Dufour et al., 2004; Dufour et al., 2006). This
has been demonstrated for short duration, steady state bouts of 10-minutes or less
(Perrey et al., 2001; Dufour et al., 2006). Studies have extended beyond 10 minutes,
however have been at maximal or near maximal workloads and did not achieve steady
state (Walsh et al., 2001; Dufour et al., 2006).
14
15
1 Male
5
N/A
Asmussen,
1952
Abbott and Bigland,
1953
Bond-Peterson,
1969
Healthy male
Healthy male
Healthy male
Healthy male
18 cyclists
Perrey et al.,
2001
Walsh et al.,
2001
Dufour et al.,
2004
Dufour et al.,
2006
Elmer et al.,
2010
Male & female
N/A
2 (3 trials each)
Abbot et al.,
1952
Bigland et al.,
1973
Bigland-Ritchie et al.,
1976
Subjects
Author,Year
Type
30 minutes
To exhaustion
6 minutes
steady sate
High intensity(peak power achievable for 2
min concentric)
3 minute step protocol to exhaustion
concentric, eccentric matched to these
workloads. Mean peak 287 W
-Heavy eccentric (270)
-Heavy concentric (270W)
-Light concentric (70 W) t
1 minute
6 minutes
-Heavy eccentric (330W)
-Heavy concentric (330W)
-Light concentric (70W)
20% of max power achievable concentrically
10-15 minutes
N/A
N/A
10 minutes
Not reported
13 minutes ,10
at steady state
Duration
Moderate (3 kg/m)e
Motorised ergometer design
Motorised ergometer design
First motorised ergometer
Adapted bicycle ridden on decline treadmill
Cycle coupled in opposition
Table 1.1: Single bout eccentric cycling literature
Determined joint contributions to force production
during eccentric cycling
At 1 L.min-1 O2 consumption concentric
workload 50 W, eccentric 250W.
For equal VO2 eccentric heart rate is significantly
higher than concentric
For same workload significantly lower oxygen
consumption, heart rate and muscle activation in
eccentric condition
Eccentric cycling not associated with impaired
oxidative function
For same workload significantly lower oxygen
consumption, heart rate and muscle activation in
eccentric condition
Lower O2 and EMG in eccentric cycling
New ergometer with improved ability to measure
work performed
New ergometer design involving an induction
clutch to allow controlled regulation of work
Related differences in oxygen consumption to
different numbers of active fibres
Found eccentric work cost less than concentric
work
concentric work always has greater oxygen
consumption than equivalent eccentric work
Findings
1.5.3 Eccentric cycling training studies
Over the past decade there have been many studies that have utilised eccentric cycling
interventions as training programs and have achieved beneficial physiological
adaptations in various populations including, young healthy adults (LaStayo et al.,
2000; LaStayo et al., 1999), elderly cohorts (LaStayo et al., 2003; Mueller et al., 2009),
individuals with cardiovascular conditions (Meyer et al., 2003; Steiner et al., 2004),
COPD (Rocha Vieira et al., 2011; Rooyackers et al., 2003), Parkinson’s disease (Dibble
et al., 2006), impaired glucose tolerance (Marcus et al., 2008), cancer survivors
(LaStayo et al., 2011), and recovery from anterior cruciate ligament reconstruction
(Gerber et al., 2006). A summary of this literature can be seen in Table 1.2. This
project is particularly interested in the potential to improve strength for low
cardiovascular stress, in the elderly and individuals with low exercise tolerance due to
central limitations. This section of the literature review will step through the first
training studies performed using young healthy subjects, then any studies that have
investigated the effect on the elderly, or individuals with cardiac conditions or COPD.
1.5.3.1 Interventions using healthy subjects
LaStayo et al. (1999) recruited nine young, healthy subjects to complete a six week
training program. Initially subjects performed two 10-minute exercise sessions and this
was increased to five 30-minute exercise sessions per week for the second half of the
intervention.
Workloads were self-selected initially, resulting in a 3 times greater
amount of work being performed in the eccentric group.
In the fifth week the
workloads were adjusted to equalise metabolic cost and this resulted in a 7 times greater
workload in the eccentric group. There was a significant strength increase of 33%
found in the eccentric training group during week 6 of the training program and was
27% higher 2-3 days after the program ceased. This was the first of the training studies
however, it was poorly controlled primarily on the basis of the varied subject pool
including male and female subjects of varied levels of physical activity. Additionally
there was no matching between the experimental and control group for the majority of
the program.
A later study by LaStayo et al. (2000) compared an eccentric and a concentric group
over an eight week training program. Thirteen healthy male subjects with a mean age of
16
23.9 years completed the intervention. Session duration was increased from two 15minute sessions in the first week to three sessions of 25 and 30 minutes in the second
and third week respectively. Four 30 minute sessions were performed in week 4 and
five 30 minute sessions were performed in weeks five and six. Weeks seven and eight
dropped back to three sessions of 30 minutes. Both groups trained at workloads that
would elicit equivalent cardiovascular loads, ranging from 54-65% of peak heart rate.
Similar to the LaStayo et al. (1999) study the eccentric group in this study performed
much higher workloads (Ecc: 489W v Con: 128W). Significant increases in isometric
leg strength were found for 7 of the 8 weeks in the eccentric training group. There was
a total pre training to post training increase of 26%. No significant differences were
seen in isometric strength in the concentric control group.
The two studies by LaStayo et al. (1999; 2000) used healthy subjects to show that when
cardiovascular load is matched, chronic high force eccentric cycling produces greater
improvements in strength than concentric cycling at equivalent cardiovascular loads.
This ability to produce high forces led LaStayo et al. (1999) to state “our long term
goal is to develop an Ecc skeletal muscle training paradigm that could be used in
clinical settings to deliver greater stress to locomotor muscles (workloads exceeding
100W), without severly stressing the oxygen delivery capacity of the cardiovascular
system”. They went on to give the examples of CHF, and COPD patients as potential
clinical cohorts which could maintain or even increase skeletal muscle strength with
low cardiovascular stress. This could potentially attenuate the low exercise tolerance
due to central limitations.
1.5.3.2 Interventions using the elderly
Due to the fact that the elderly suffer decrements in muscle function, as do individuals
with pathologies, the elderly are a good intermediate step between healthy young
individuals and groups with pathologies. Although there are similarities in muscle
function, it is well known that muscle function in elderly individuals is superior to agematched controls with CHF (Minotti et al., 1993) and COPD (Gagnon et al., 2013).
LaStayo et al. (2003) used 21 frail elderly subjects with a mean age of 80 years to
perform an 11-week training intervention. The experimental group performed eccentric
17
cycling while the control group performed traditional free weights and weight machines
(leg press, leg extension, mini squat).
Both groups performed 10-20 minutes of
exercise, 3 times per week for the 11-week program. The training intensity was initially
set at a level so the subject was working at the lowest perceived effort “very, very light”
and increased to a perceived effort of “somewhat hard” on a 15-point rating of
perceived exertion scale (Borg, 1962). The traditional weights group increased their
load when 10-15 repetitions became easy the resistance was increased to a level where
6-10 repetitions became hard. Both eccentric and traditional weights groups achieved a
significant increase in muscle fibre cross sectional area. The eccentric group increased
fibre size by 60% and the traditional group increased by 41%, however only the
eccentric cycling group achieved a significant increase in isometric quadriceps strength
which improved by 60%, balance which improved by 7% and stair decent performance
which improved by 21%. There was an improvement in the eccentric and control group
for the timed up and go test however only the eccentric group changed their falls risk
from high to low. In this study the workloads were determined via subject’s own level
of perceived exertion and not calculated by any pre-determined physiological variable.
Even though the workloads were adjusted to maintain an exertion rating of “somewhat
hard”, subjects were still able to maintain very high power outputs. The most frail
subject was an 89 year old who relied on a cane, but was able to maintain 216W of
eccentric work over a 15-minute period.
A 12-week training study using 62 elderly men and women also achieved a significant
improvement (8.4%) in isometric leg extension strength which was not achieved in the
conventional resistance training control group (Mueller et al., 2009). The eccentric
sessions were 20 minutes in duration plus a warm up and cool down. The workload for
the eccentric sessions started low at 70W and was increased over the 12 weeks to a
workload of 315W. The conventional resistance training program consisted of 2 sets of
8-10 repetitions for leg press, leg extension, leg curl and hip extension. Once a subject
could perform 10 repetitions, the load was increased for the next session. A significant
increase in relative lean thigh tissue was seen, however this appears to be more related
to a decrease in cutaneous adipose tissue rather than hypertrophy of muscle fibres.
Neither the conventional nor eccentric groups had a significant change in the Berg
18
Balance Scale scores, however both groups significantly improved in the timed up and
go test.
LaStayo et al. (2003) and Mueller et al. (2009) have both demonstrated that training
programs using eccentric cycle ergometry are an effective way of increasing lower limb
strength in an elderly population. The two studies showed significant increases in
functional performance tests as well as in isometric strength, indicating that the strength
changes achieved would have a positive impact on functional status.
1.5.3.3 Interventions using subjects exercise intolerance
Exercise intolerance can leave individuals unable to exercise at intensities high enough
to improve strength (Hanson, 1994). The eccentric studies using healthy young adult
and elderly populations have shown that for equal metabolic work, eccentric cycle
ergometry can generate much higher forces and elicit improvements in strength and
functional capacity. This appears to have great benefit for individuals with CHF and
COPD and may help maintain or increase strength and therefore functional status
(LaStayo, et al., 1999).
Meyer et al. (2003) recruited 13 male patients with coronary artery disease and
randomly allocated them into an eccentric or a concentric training group. Each subject
performed three 30 minute sessions per week for an eight week period. The training
intensities for each group was set to elicit 60% of peak oxygen uptake or 85% of max
heart rate. There was a progressive increase in training workloads which was identical
between both groups. The rate of increase in workload was determined by avoiding any
muscle soreness. In this pathology group, the matching of training loads using oxygen
consumption enabled the eccentric group to produce a markedly higher maximum
power output of 357W versus 97W performed by the concentric group. Throughout the
eccentric sessions mean arterial pressure, systemic vascular resistance, pulmonary
capillary pressure, cardiac index and stroke work were all within an acceptable (normal)
range, leading to the recommendation that eccentric cycling is a safe and suitable
exercise modality for low risk patients with coronary heart disease. Unfortunately, this
study had no measures of isometric or functional strength.
19
Steiner et al. (2004) performed an 8-week training study in middle aged men with
coronary artery disease. An eccentric and concentric control group performed training
sessions 3 times per week and progressed equally to an intensity of 60% VO2 peak,
resulting in an average concentric workload of 97W versus an average of 338W in the
eccentric group. This resulted in an 11% increase in peak isometric torque and a 15%
and 9% increase in concentric peak force at 60o.second-1 and 120o.second-1. Contrary to
their hypothesis and the earlier results of LaStayo et al. (2000; 2003) there was a
significant muscle cell hypertrophy achieved by the concentric control but not by the
eccentric group.
Rooyackers et al. (2003) had two groups of COPD patients performing either general
exercise training or a combination of general and eccentric exercise ergometry. The two
groups did equal time at equal metabolic intensities. The workload that could be
achieved during a 15 minute eccentric cycling session was 160W. The results showed
that both groups achieved equivalent improvements in exercise capacity, however
eccentric cycling is more attractive to COPD patients as they report less dyspnoea and
can maintain a level of conversation while training. No measures of strength were
taken, so it is unknown whether the considerably lower, 160W workload would achieve
improvements in strength.
A feasibility study had 6 patients with severe COPD undertake a 5-week program
consisting of 3, 20 minute sessions per week. The goal was to progressively increase
the workload over the 15 sessions to reach a VO2 of 60% of concentric peak. This was
achieved with an average workload of 146W in the final week. This is very similar to
the 146W average workload achieved by Rooyackers et al. (2003). Unfortunately no
strength measurements were collected.
The combination of these four studies has shown that eccentric cycling can be achieved
in individuals with coronary artery disease and COPD with high compliance and no side
effects. The two studies looking at coronary artery disease have shown that high forces
of greater than 300W can be achieved in patients with coronary artery disease, however
COPD patients could only achieve considerably lower workloads of less than 200W.
Steiner et al. (2004) demonstrated improvements in strength can be achieved at high
20
force similar to those used in healthy and elderly patients. Unfortunately neither of the
low force studies with COPD measured strength adaptations.
1.5.3.4 Training studies summary
Training studies using high force eccentric cycling of greater than 300W has
collectively demonstrated significant improvements in isometric strength. The extent to
which eccentric cycling induces hypertrophy is inconsistent with some studies finding
significant increases (LaStayo et al., 2003; LaStayo et al., 2000) and some finding none
(Steiner et al., 2004). Although it has been shown that certain pathology cohorts, such
as coronary artery disease, respond well to the high force training at 60% of VO2 or
60% of heart rate max (Steiner et al., 2004), it is not necessarily suitable for everybody
as demonstrated by the low forces achieved in COPD populations (Rocha Vieira et al.,
2011; Rooyackers et al., 2003). This could confirm the statement by Hanson et al.
(1994) that exercise intolerance may inhibit some individuals from exercising at an
intensity high enough to increase strength.
CHF is another condition expected to
respond similar to COPD due to an inability to deliver adequate oxygen to working
muscles during exercise (Zeng and Jiang, 2012). The Exercise and Sports Science
Australia position statement on exercise training for chronic heart failure recommends
aerobic training intensities between 40-70 % of VO2 peak for NYHA class 1-4 or
between 40-75% of heart rate peak (Selig et al., 2010). In particular, the position
statement states class 3-4 heart failure should exercise between 40-60% of VO2 peak for
continuous based aerobic exercise. This would mean that all of the papers that reported
the intensities of 60% VO2 peak would be at the absolute upper end of the
recommendations and it would be useful to determine whether eccentric ergometry
training at lower intensities would still induce improvements in strength. There is some
evidence to suggest that higher intensity interval training can be used as an alternative
method of increasing aerobic capacity, in particular VO2 peak (Wisloff et al., 2007).
Although high intensity interval training shows promise as an exercise alternative for
CHF patients, most studies employing this form of exercise are using subjects with
ejection fractions above 25% (Wisloff et al., 2007).
Caution should be used in
extrapolating these findings to individuals with severe exercise intolerance and ejection
fractions less than 20%. Individuals with more progressed or sever conditions may not
be able to achieve such high workloads. This inability for such individuals to produce
21
high workloads is demonstrated in a recent study using severe COPD patients, who
could only average a workload of 10W in the first week of an eccentric cycling training
intervention.
22
Table 1.2 Chronic eccentric cycling studies
Author, year
Subjects
LaStayoet al.,
1999
9 healthy subjects
of different
gender and
activity levels
LaStayoet al.,
2000
14 healthy male
Training
intervention
6 weeks, building to
a max of 5 * 30 min
sessions/week
VO2 equalised
8 weeks, building to
a max of 5 * 30 min
sessions/week
Eccentric load
Findings
High load
(400-500W)
Significant isometric leg
strength increases in the
eccentric group only
Progressively
increasing to an
average of 489 W.
The eccentric group
achieved significant
isometric strength gains and
increases in cross-sectional
area not seen in the
concentric group
LaStayoet al.,
2003
21 frail elderly
11 weeks, 3 * 10-20
min/week
216-400W
Significantly improved
strength, balance, stair
descent time and timed up
and go. Moved from high
risk of falls to low
Mueller et al.,
2009
62 elderly men
and women
12 weeks 2*20
min/week
70-315W
Significantly improved leg
extension strength and
balance.
Meyer et al.,
2003
13 male coronary
artery disease
patients
8 weeks, 3*30 min
@ 60% peak VO2 or
85% peakHR
Peak power of
375W
Significant increase in peak
power and peak VO2
Rooyackers
et a.l, 2003
24 COPD
10 weeks
Max achievable
for 15 min
No strength measurements
Rocha Vieraet
al.,
2011
6 male COPD
5 weeks, 3 * 20 min
targeting 60% of
peak VO2
Progressive from
a mean of 10 W to
146W
7 fold higher workrate in
week 5 than at baseline
No strength measurements
Steiner et al.,
2004
12 coronary artery
disease
8 weeks, 3*30 min
@ 60% peak VO2
338W
12 weeks, 3.week-1
Not reported
Marcus et al.,
2009
16 women with
impaired glucose
tolerance
LaStayoet al.,
20 Older cancer
2010
survivors
Significant increases in
isometric and concentric
strength
Increased lean muscle mass,
strength and 6 minute walk
test without affecting
insulin sensitivity
12 weeks, 3*3-20
min
(eccentric stepper
Not reported
Increased isometric strength
Improved up and go test
not cycle)
LaStayoet al.,
2011
40 Cancer
survivors
12 weeks, 3*3-20
min
(eccentric stepper
not cycle)
23
Not reported
Increased strength, muscle,
cross sectional area, six
minute walk distance and
stair descent time
1.6 Concluding comments
The acute effects of a single bout of eccentric cycling have clearly demonstrated that
when eccentric and concentric cycling are matched for metabolic work that eccentric
cycling can generate much higher forces.
It is also clear that if eccentric cycle
ergometry is performed at equivalent absolute loads that metabolic cost, cardiovascular
work and neuromuscular activation are significantly lower in the eccentric group.
These studies have been performed with either short duration or high force protocols.
Although many eccentric cycle ergometry training studies have been performed, to our
knowledge the metabolic cost of a longer duration bout of low load eccentric cycling
has never been tracked. The training studies have performed sessions in this duration
and have made the assumption that longer duration sessions will maintain the low cost
characteristics of shorter duration sessions.
Additionally training studies have clearly demonstrated that repeated high force
eccentric cycle ergometry (>300W) significantly improves strength and in some cases
has significantly increased muscle fibre size. Although it is known that the average
sustainable workload of COPD patients during eccentric cycling is less than 200W it
has never been determined if training at these workloads will provide a large enough
stimulus to increase strength. The ability of high force eccentric training to increase
strength in the literature is very valuable information however as stated by Hortobagyi
(2003), the dose response for eccentric cycling is unknown. This project will attempt to
determine if lower force eccentric cycling can produce improvements in strength. This
is the original goal outlined by LaStayo et al. (1999) but is still yet to be determined.
24
1.7Aims and Hypothesis
The overall aim of this project was to examine the efficacy of low force eccentric
cycling as an exercise training modality for improving muscular strength. It is broken
into two specific studies. Study 1 determined the acute cardiovascular, metabolic and
neuromuscular response to a single 30 minute bout of eccentric cycling. Study 2 was an
8-week training study in sedentary males to determine functional adaptations to
repeated bouts of low load eccentric cycling.
Study one:
This study was conducted using 6 healthy males and 6 healthy females with a mean age
of 22 years.
Each subject performed 30 minutes of eccentric (experimental) or
concentric (control) cycling in a randomised cross-over design. Subjects acted as their
own control.
Aim one: To validate the custom built eccentric cycle ergometer and determine
whether the results produced correspond with those reported in the literature.
Hypothesis one: That 30 minutes of low load eccentric cycling will elicit a
lower cardiovascular and metabolic cost than equal force concentric cycling for
a duration up to 30 minute period.
Aim two: To quantify the familiarisation process of the initial three sessions of
eccentric cycling and to determine the precision of actual work performed in
relation to the desired target workload.
Hypothesis two: That the precision of the mean work performed will improve
systematically over the first three eccentric cycling sessions and variability will
systematically decrease.
Aim three: To measure the time course of muscle soreness and determine
whether a reduction in muscle soreness relates to work performance during the
eccentric cycling familiarisation process.
Hypothesis three: That muscle soreness will subside prior to improvements in
eccentric work performance, demonstrating that a reduction in muscle soreness
is not a sufficient indicator of adequate familiarisation.
25
Study two:
The second study in this project builds on data obtained from the first study to carry out
a training study with 17 sedentary male subjects.
Subjects were allocated to an
eccentric or concentric training group for 8 weeks: The aims of study 2 are:
Aim four: To determine whether eight weeks of repeated low load eccentric
cycling at low cardiovascular workloads can produce improvements in lower
limb muscular strength.
Hypothesis four: Eight weeks of repeated eccentric cycling will produce
improvements in isometric and functional strength relative to those achieved in
the concentric control group.
Aim five: To determine whether eight weeks of low load eccentric cycling will
produce alterations to resting physiological measurements of heart rate, blood
pressure or heart rate variability.
Hypothesis five: There will be no changes in resting physiological
measurements after eight weeks of low load eccentric cycling as the
cardiovascular stimulus will be too low to induce adaptations. The greater
aerobic workload in the concentric control group will induce greater resting
cardiovascular improvements than the eccentric group.
Aim six: To extend the familiarisation process to five sessions, beyond the three
of study one, and quantify the precision of actual work performed compared to
the desired target workload.
Hypothesis six: That the precision of the work performed will systematically
improve until the average achieved workload matches the desired target
workload. Beyond this point the mean work performed will remain consistent
but variability will continue to decrease.
26
Chapter 2: Acute physiological response to 30 minutes of eccentric
cycling.
2.1 Introduction
Eccentric cycling is an exercise modality that has been proposed as a potentially
suitable method of increasing skeletal muscle strength at low cardiovascular cost
(LaStayo et al., 1999). In order to specifically design exercise protocols for groups
with low exercise tolerance it is necessary to determine the acute cardiovascular
response to an extended duration bout of submaximal low load eccentric cycling.
While studies have demonstrated that short duration bouts of 10-minutes or less appear
to possess suitable attributes (Perrey et al., 2001; Dufour et al., 2006), this is shorter
than the ACSM recommendations for exercise duration (Garber et al., 2011). Therefore
further work needs to be conducted to determine the response over longer periods of
exercise. The only studies to extend the exercise duration beyond 10-minutes, did so at
maximal or near maximal workloads (Walsh et al., 2001; Dufour et al., 2006). For
some pathologies such as COPD and CHF high force eccentric cycling has been
achievable (Meyer et al., 2003; Steiner et al., 2004). This however may not be the case
in cohorts with severe symptoms leaving lower loads as a viable option worth
investigation. An example of this is a cohort of patients suffering severe COPD that
could only maintain an initial mean workload of 10W (Rocha Viera et al., 2011). As no
studies have looked at low to moderate force eccentric cycling beyond 10 minutes this
is a gap that will need to be filled if eccentric cycling is going to be utilised as a training
tool. The current ACSM guidelines for exercise is 30 minutes or greater of moderate
intensity exercise on five or more days per week, or 20 minutes or greater of vigorous
intensity exercise (Garber et al., 2011). This will determine whether the lower
cardiovascular and metabolic response to acute eccentric cycling remains consistently
lower, or if a cardiovascular drift occurs bringing the two conditions closer together as
session duration increases.
Therefore, the purpose of this study was to determine the cardiovascular, metabolic and
neuromuscular response to a 30 minute bout of low load eccentric cycling. The study
used a randomised cross-over design where individual subjects acted as their own
control. Heart rate, oxygen consumption and muscle activation were measured
throughout the 30 minute sessions to give an indication of cardiovascular, metabolic
27
and neuromuscular stress respectively.
It was hypothesised that the metabolic,
cardiovascular and neuromuscular demand of eccentric cycling will remain lower for
eccentric cycling throughout the entire thirty minute protocol. This provides additional
evidence that eccentric cycling is a potentially beneficial modality for increasing
muscular strength with low stress on the cardiovascular system.
28
2.2 Methods
2.2.1 Equipment
2.2.1.1 Custom built cycle ergometer
A cycle ergometer (Figure 2.1) was custom built to enable independent concentric and
eccentric workloads. The ergometer was in a semi-recumbent position and was
equipped with a 240 Volt, 0.75kW asynchronous electric motor (MasterDriveSimovert
Vector Control, Siemens, Erlangen, Germany) to produce the force that needs to be
resisted in the eccentric mode in addition to the usual concentric mode. The seat and
hand grips were adjusted for individual anthropometry.
The custom built ergometer used in this study is more advanced than other ergometers
reported in the literature. This is primarily due to utilising a power measurement system
modified from competitive cyclists. This has allowed a more thorough quantification of
the familiarisation process to eccentric cycling and the work performed during the 30
minute exercise bouts. More information about this system is provided below in section
2.2.1.4.
2.2.1.2 Eccentric Mode
In the eccentric mode the pedals were driven backwards by a 0.75kW asynchronous
electric motor. Work was measured using the SRM powercrank system. More detail is
provided below about the SRM system.
2.2.1.3 Concentric Mode
The concentric component of the ergometer used an existing magnetic braked work
regulation box (Siemens, CAmed, Germany ). The voltage control to the magnet is a
dial and workload can be adjusted in 10 or 20W increments. Pilot testing in the lab
validated the accuracy of the concentric workload using the SRM powercrank system.
29
2
3
1
4
A.
B.
Figure 2.1 (A) The custom built eccentric ergometer. shows; (1) electric motor, (2) concentric mode
control unit, (3) magnetic brake for concentric mode and (4) power crank system. Figure 2.1B is a
close up of the powercrank system. The dashed circles represent the location of the load cells
30
2.2.1.4 Schoberer Rad Meβtechnik (SRM) PowerCrank
A Schoberer Rad Meβtechnik (SRM) PowerCrank system (Schoberer Rad Meβtechnik,
Julich, Germany) directly measured the power applied at the cranks during cycling via
four strain gauges (2.5% 0-1000W) mounted inside the chain ring of the right crank.
The strain measured in volts and was converted to a frequency signal and relayed to a
wireless SRM PowerControl V1 data logger which converted the output frequency to
power (W). Power (W), cadence (revs.min-1) and heart rate (beats.min-1) data was
recorded second by second using the SRM Powercontrol V1 unit was downloaded to a
personal computer. The SRM system has been validated by Gardner et al. (2004).
2.2.2 Subjects
Twelve healthy subjects, six male and six female university students, with a mean age
of 21.2 ± 2 years participated in the study. Subjects were recruited from within the
university using email and in lecture advertisements. Twelve subjects were chosen
based of the sample sizes used in similar studies in the literature. Prior to participation
all subjects were interviewed and screened for musculoskeletal injuries and
cardiorespiratory conditions. The participant screening document can be seen in
appendix A which highlights the screening that was conducted. Written consent was
obtained prior to participation, and all protocols were approved by the University of
Wollongong Human Research Ethics Committee (HE08/215).
2.2.3 Experimental Standardisation
Subjects were required to refrain from strenuous exercise and consumption of alcohol
for the 12 hours prior to each laboratory session. Subjects were also instructed to avoid
caffeine and tobacco for the 2 hours prior to all testing or training sessions. All testing
was conducted at a similar time of day between 0900 and 1700 hours in a room where
temperature was controlled at an average of 18oC. A single tester conducted all sessions
in order to avoid inter-tester variation.
2.2.4 Experimental design
After screening was completed all subjects performed a maximal aerobic step test on
the recumbent cycle in the concentric mode. The peak workload determined from this
test was used to determine workloads for the subsequent sessions. All subjects
performed 3 familiarisation sessions in the eccentric mode with workload set at 60% of
31
the peak workload achieved in the maximal aerobic test. After the familiarisation
sessions, a random cross over method was used to determine trial order for the 30
minute testing sessions. The experimental design is illustrated in Figure 2.2.
Subject Screening
n=12
Peak Workload Test
n=12
Familiarisation
n=12
Concentric mode
n=6
Eccentric mode
n=6
Eccentric mode
n=6
Concentric mode
n=6
Figure 2.2: Study one experimental design
32
2.2.5 Peak workload test
All subjects initially performed a maximal aerobic step test on the custom built
recumbent cycle ergometer, in the concentric mode to determine the maximal aerobic
workload. The step protocol began at 20W and increased workload at a rate of 30W per
minute, at a set cadence of 65 rpm until volitional exhaustion. Power (W), cadence
(revoltions.min-1) and heart rate (beats.min-1) data were recorded second by second
using the SRM power crank system.
Peak workload was measured as the final
workload that was achieved in the test prior to exhaustion and was used to determine
training intensities for the subsequent testing sessions.
2.2.6 Familiarisation
All subjects completed three familiarisation sessions to become accustomed to the
unusual technique required for the eccentric cycling protocol. Familiarisation sessions
involved a 5 minute, self-selected concentric warm up, a 10 minute eccentric
familiarisation session at 60% of peak aerobic workload, and a 5 minute concentric cool
down. Familiarisation sessions were separated by 3-5 days. Subjects received visual
biofeedback via the SRM data logger display. They were required to adjust their output
to maintain the desired workload. The tester was also monitoring the data logger to
ensure that there was a legitimate attempt to maintain the desired workload. The 10
minute eccentric bout was performed at a fixed cadence of 65 RPM, at 60% of the peak
workload achieved in the concentric max test.
2.2.7 Thirty minute submaximal test protocols
Subjects performed two acute 30 minute trials, one in the concentric mode and one in
the eccentric mode. The trial order was randomised to minimize the effect of test
familiarisation and acclimation. Baseline data was collected for 2 minutes at rest. The
30 minutes of exercise was divided into three distinct 10 minute blocks. Block 1
consisted of two collection periods. The first at 3-5 minutes, to represent steady state,
pre fatigue values and the second at 8-10 minutes, to represent the end of the first
exercise block. Data was also collected in the last 2 minutes of block 2 and block 3.
Sample periods can be seen below in Figure 2.3.
33
Baseline Measurements
O2, HR, EMG
Collection Period 1
Pre-fatigue
O2, HR, EMG, Pow, Cad
10 minute
cycling Block 1
Collection Period 2
8 – 10 minutes
O2, HR, EMG, Pow, Cad
1 min rest
Collection Period 3
18 – 20 minutes
10 minute
cycling Block 2
O2, HR, EMG, Pow, Cad
1 min rest
Collection Period 5
28 – 30 minutes
10 minute
cycling Block 3
O2, HR, EMG, Pow, Cad
Figure 2.3 Thirty minute session design showing data collection periods. O2 indicates oxygen
consumption measurements were taken. HR indicates heart rate measurements were taken.
EMG indicates surface electromyography was collected. Pow indicates work performed was
measured and Cad indicates cadence was recorded. A short 1 minute rest was taken after
collection periods 2 and 3 to allow the tester to perform equipment checks.
34
2.2.8 Measurements
2.2.8.1 Power, Cadence and Heart Rate
Power, cadence and heart rate data were collected second by second throughout the
sessions. Heart rate was detected using a polar chest strap (Polar Electro Sport Tester,
Finland) that received and transmitted data to the SRM control unit. Polar heart rate
monitor measurements have been validated for accuracy during stationary laboratory
tasks (Goodie et al., 2000). Heart rate data points that returned as zero were excluded
as measurement error due to poor electrode contact.
Power, cadence and heart rate
data for these sessions was presented as an average over the entire 10 minute period.
Standard deviation was also calculated on the power data to represent the variability of
the work performed over the session.
2.2.8.2 Muscle Soreness
Subjects were required to complete a visual analogue scale (VAS) in regards to muscle
soreness of the legs at time periods 5 minutes, 24 hours, 48 hours and 72 hours after the
familiarisation sessions (Cleak & Eston, 1992). The visual analogue scale can be seen
in Figure 2.4. Subjects were instructed to complete the scale while standing, and were
required to draw a vertical line bisecting a horizontal line. One end of the line
represents “no pain” and the other end “worst pain imaginable”. The distance of the
bisecting line was measured and quantified as a fraction by dividing the distance from
the start of the line to the identified point, divided by the total length of the line.
How severe is your pain?
No Pain
Worst pain imaginable
Figure 2.4. Visual Analogue Scale (VAS). Used to quantify subjects muscle soreness after the initial
3 familiarisation sessions.
35
2.2.8.3 Metabolism
Expired gas samples were collected during the four 2 minute sampling periods.
Standard respiratory parameters; tidal volume (L), breathing frequency (breaths.min-1)
and expired gas composition (%) was measured using mixing chamber gas analysis,
with the 2900c Metabolic Measurement Cart (SensorMedics Corporation, Yorba Linda,
CA, USA). The system was calibrated using ambient temperature (oC), pressure
(mmHg) and humidity (%) as measured by a wet/dry bulb thermometer and barometer
located in the testing room. Oxygen and carbon dioxide gas analysis was calibrated
using alpha gas standards (15.97% oxygen, 4.03% carbon dioxide, balance Nitrogen).
The system was be calibrated for volume using a 3.012 Litre calibration syringe.
Subjects inspired room air through a one way valve (Hans Rudolf inc, Shawnee, KS,
USA) and expired directly into the metabolic measuring cart.
2.2.8.4 Electromyography
Surface Electromyography (EMG) was recorded using bipolar Ag-Agcl adhesive cloth
electrodes with a surface diameter of 15mm (3M). EMG signals were pre amplified
with a low frequency cut off to 3 Hz, amplified 1000 times (Neurolog 844, 820, 144,
135, DigitimerNeurolog, Hertfordshire, U.K). The signal was filtered with a high pass
range of 500 Hz and low pass range of 10 Hz via the Power 1401 analogue to digital
converter (Cambridge Electronic Design, Cambridge, U.K.). Data was collected for
each channel at 1000 Hz. All electrode sites were initially shaved using a razor, abraded
and cleaned using an alcohol swab. The muscles of interest were the quadricep group
and involved measurement of EMG activity at three sites. The sites were carefully
measured using pronounced anatomical landmarks as references (Cram & Kasman,
1988). The three muscles measured for EMG were the rectus femoris, vastuslateralis
and the vastusmedialis. All electrode placement measurements were taken with the
subject standing. The rectus femoris electrode was placed half the distance between the
anterior superior iliac spine and the base of the patella with an inter-electrode space of 2
cm, parallel to the muscle fibre direction. The Vastuslateralis electrode was placed two
thirds of the distance between the greater trochanter and the base of the patella with an
inter-electrode space of 2 cm. The electrodes will be on an oblique angle just lateral to
the midline. The vastusmedialis electrode was placed 2 cm medial to the superior rim of
36
patella with the electrodes set at an oblique angle of 55 degrees, with a 2 cm interelectrode distance. Subjects had electrode positions marked with permanent ink and
marks were maintained to ensure reproducibility. Data was analysed for Root Mean
Squared (RMS) using Spike 2 software (V5.13) (Cambridge Electronic Design,
Cambridge, U.K.). Program scripts were written to minimise error. Four data collection
points were analysed, the first at minutes 3-5 to represent steady state pre fatigue values
and 3 more taken for the last 2 minutes of each block. The raw signal was rectified and
then an average RMS was calculated for two 10 second samples with in the 2 minute
period. An average of the two samples was used to represent mean RMS for each 2
minute period. These values are expressed to represent total quadriceps activity.
A.
B.
C.
Figure 2.5: Photographs of surface electromyography electrode placement. (A)ink markers for the
rectus femoris electrode. The cross in the centre is the measured position with the two small dots
either side marking the centre of the electrodes with an inter-electrode spacing of 2cm. (B) shows
the rectus femoris, vastuslateralis and vastusmedialis electrode placement. (C)shows the rectus
femoris electrodes with cables attached.
2.2.9 Statistical Analysis
Subject characteristic data of age, height, mass and BMI were reported as mean ± SD.
All other experimental data was reported as mean ± SEM. Physical attributes are
presented as mean ± SD as it is used to describe the variation in measurements of a
variable within a sample population (Sedgwick, 2011). Mean ± SEM is used for the
physiological measurements as it is better used to describe the precision of a sample
mean (Sedgwick, 2011). A one-way repeated measures ANOVA was used to determine
within group differences over the familiarisation sessions or 30 minute exercise bouts (p
≤ 0.05). A two-way ANOVA was used to determine a between group difference
throughout the 30 minute exercise bouts.
Linear regressions were performed to
determine the correlation between muscle soreness and power output and also between
muscle soreness and power output variability.
37
2.3 Study One Results
2.3.1 Subject characteristics
Twelve healthy subjects completed the study (male n=6 female n=6) with a mean age of
21 ± 2 years. Subjects were active and healthy with a mean BMI of 23.8 ± 4.1. The
mean peak workload was 264 ± 62 W and the mean peak heart rate was 176 ± 14
beats.min-1. Prior to participation, subjects were screened for musculoskeletal problems
or any other contraindications to exercise. All procedures were approved by the
University of Wollongong Human Research Ethics Committee (HE08/215). Individual
subject data can be seen in Table 2.1.
38
Table 2.1: Subject characteristics
BMI
Peak
workload
(W)
Peak
heart rate
(beats.min
-1)
Subject
Sex
Age
(years)
1
Male
20
1.78
105
33.1
310
198
2
Male
20
1.83
83
24.8
320
178
3
Male
22
1.8
80
24.7
310
169
4
Male
26
1.82
81
24.5
260
175
5
Male
21
1.77
73
23.3
340
156
6
Male
21
1.75
79.5
26.0
350
184
7
Female
19
1.63
71.5
26.9
230
186
8
Female
20
1.73
62.5
20.9
220
192
9
Female
24
1.66
67
24.3
260
176
10
Female
20
1.7
50
17.3
180
156
11
Female
20
1.64
50
18.6
160
161
12
Female
21
1.64
57.5
21.4
230
186
21 ± 2
1.73 ± 0.07
71.7 ±15.7
23.8 ± 4.1
264 ± 62
176 ± 14
Mean ± SD
Height (m)
Weight
(kg)
Individual subject characteristics and group mean ± SD. Height and weight data collected in intial
session. Peak workload and heart rate data collected during incremental peak concentric cycling
test.
39
2.3.2. Eccentric work performed during familiarisation
The mean work performed is used to determine whether the total work performed
between the concentric and eccentric conditions was equal. Individual data can be seen
in Table 2.2 and group data in Figure 2.6A. All subjects (n=12) performed three, 10
minute familiarisation sessions at 60% of the peak workload achieved in the maximal
exercise test. The mean target workload for the familiarisation sessions was 158.5 ±
37.38W. In the first session subjects were unable to achieve the target workload with an
actual workload achieved of 130.3 ± 13.0W, 28 .2W lower than the target. The work
performed in the second session increased to 150.1 ± 14.3W and in the final
familiarisation session the actual work achieved was 159.6 ± 13.0W. The achieved
work in the third familiarisation session was within 1 % of the desired target workload.
2.3.3 Variability of work during familiarisation
Where the mean work performed was used to determine the total work, the variability
of the work provides insight into the consistency of the eccentric work. A lower
variability would indicate a more consistent performance. The two calculations of
variability, standard deviation of the second by second power data and coefficient of
variation (C.V.), both demonstrated a systematic decrease in variability over the three
familiarisation sessions. Mean data can be seen in Figure 2.6B. The variability of work
systematically decreased over the three familiarisation sessions from 50.0 ± 12.9W to
36.0 ± 10.0W to 30.5 ± 10.2W respectively from the first to third familiarisation
session. The C.V. results confirmed the results of the standard deviation calculations
and showed a systematic decrease from 0.45 ± 0.26 to 0.29 ± 0.21 then 0.22 ± 0.13
from the first to third sessions respectively. The standard deviation and C.V. data
showed a significant decrease in variability from the first to second session but no
significant difference from the second to third.
40
Figure 2.6: Eccentric power output during familiarisation sessions. Percentage of target power
output (A), and power output variability throughout 10 minute familiarisation sessions one (F1),
two (F2) and three (F3). Data presented as mean ± SEM. n=12 for all three sessions. * indicates p ≤
0.05. The dashed line in (A) indicates the average target power output of 158.5 W.
41
42
98.1
99.3
101.2
86.7
105.6
101.6
71.6
104.6
88.0
107.2
52.2
98.6
92.4 ± 4.7
91.6
81.5
90.9
90.0
90.3
88.1
55.9
49.8
71.7
114.0
61.4
87.7
80.5 ± 5.3
1
2
3
4
5
6
7
8
9
10
11
12
Mean ± SEM
99.6 ± 3.8
101.7
69.8
98.8
93.3
127.3
99.4
100.9
104.6
91.6
102.3
109.2
98.0
F3
Individual familiarisation data with session mean ± SEM
F2
F1
Subject
Work performed
(% of target)
Table 2.2: Familiarisation summary
50 ± 4
46
57
39
43
66
28
61
55
46
49
73
37
F1
36 ± 3
32
46
20
30
54
37
32
42
31
35
49
24
F2
0.38
0.45 ± 0.08
31 ± 3
0.97
0.32
0.38
1.01
0.36
0.33
0.30
0.33
0.29
0.47
0.22
F1
0.29 ± 0.06
0.24
0.92
0.17
0.22
0.39
0.37
0.15
0.20
0.23
0.19
0.26
0.13
F2
0.20
0.58
0.21
0.19
0.35
0.21
0.11
0.16
0.16
0.17
0.15
0.12
F3
0.22 ± 0.04
Coefficient of Variation
(C.V.)
28
39
22
28
58
28
23
33
23
32
31
22
F3
Variability of work performed
(standard deviation)
2.3.4 Muscle Soreness
The magnitude of muscle soreness for all four time periods systematically decreased
from the first to the third session. Muscle soreness was present 5 minutes after the first
session, peaked at 24 hours, and systematically decreased beyond 24 hours for all three
familiarisation sessions. Muscle soreness at the 24, 48 and 72 hour time points were
significantly lower for the second and third session compared to the first. Eleven of
twelve subjects returned complete VAS recordings. One subject was excluded for
failure to return completed data sheets. Muscle soreness individual data can be seen in
Table 2.3 and grouped data in Figure 2.7.
Figure 2.7: Muscle soreness following familiarisation sessions. Muscle soreness measured using a
Visual Analogue Scale (VAS) for sessions one (F1), two (F2) and three (F3). Data presented as
mean ± SEM. n=11 for all three sessions. * indicates significant within group difference compared
to F1 (p ≤ 0.001). † indicates significant within group difference compared to F1 (p ≤ 0.01).
43
44
52
11
0
7±5
9
10
11
Mean ±
SEM
40 ± 6
39
40
47
79
5
49
19
37
21
59
45
24 hr
33 ± 5
34
38
42
50
13
37
5
45
19
65
19
48 hr
Familiarisation Session 1
11 ± 3
7
25
8
18
2
22
0
17
0
17
8
72 hr
5±2
0
26
8
12
3
0
0
0
0
0
2
5 min
16 ± 7
0
40
1
51
56
4
0
20
0
3
2
24 hr
10 ± 4
0
38
2
20
13
2
0
32
0
0
2
48 hr
Familiarisation Session 2
2±1
0
13
2
0
0
0
0
10
0
0
2
72 hr
2±1
0
12
7
2
0
0
0
0
0
0
0
5 min
5±3
10
38
0
8
0
0
0
0
0
0
3
24 hr
3±3
0
37
0
1±1
0
13
0
0
0
0
0
0
0
0
0
0
0
72 hr
0
0
0
0
0
0
48 hr
Familiarisation Session 3
Individual muscle soreness data and group mean ± SEM. Muscle soreness data collected using a visual analogue scale and presented as a percentage
of soreness.
9
8
0
5
0
0
4
7
0
3
0
0
2
6
0
5 min
1
Subject
Table 2.3: Muscle soreness during and after familiarisation
2.3.5 Using muscle soreness as an indicator of familiarisation
The results of this study demonstrate a weak relationship between muscle soreness and
both measures of work performance. A linear regression between muscle soreness and
percentage of target workload (Figure 2.8A) resulted in an R2 = 0.1917 and a correlation
between muscle soreness and work variability (Figure 2.8B) resulted in an R2 = 0.1582.
This poor relationship raises the question that if the absence of muscle soreness was
used as an indication of successful familiarisation in other studies, how confident can
the researchers be that the desired amount of work was actually performed. Eleven
subjects had complete data sets for muscle soreness, work performed and work
variability that were used for the linear regression’s.
45
Figure 2.8: A lack of linearity between (A) % of target power output (B) power output variability
and muscle soreness 24 hours after familiarisation sessions one, two and three. N = 11 for all 3
sessions in graph A and B.
46
2.3.6 Oxygen Consumption
At rest, subjects displayed no difference in resting oxygen uptake (Con: 6.2 ± 0.4
mL.kg.min-1, Ecc: 5.9 ± 0.4 mL.kg.min-1). Once exercising there was an increase in
both concentric and eccentric oxygen uptake (Con: 32.0 ± 1.0 mL.kg.min-1, Ecc: 11.0 ±
0.7 mL.kg.min-1). This increase was significantly higher within groups compared to
baseline but the concentric group was significantly higher than the eccentric. Over the
10, 20 and 30 minute time points the concentric oxygen consumption continued to
climb where the eccentric peaked at 10 minutes and began to drop. The final 30 minute
oxygen uptakes were 36.6 ± 1.4 mL.kg.min-1and 10.8 ± 0.7 mL.kg.min-1. Figure 2.9
demonstrates that the concentric group took longer to reach steady state.
Individual
data can be seen in Table 2.4. Figure 2.9 also shows that at all exercising time points
oxygen uptake is significantly greater in the concentric group.
47
Figure 2.9: Oxygen consumption throughout a 30 minute bout of concentric  or eccentric 
cycling at 60% of peak concentric workloads. Data recorded at baseline, 5, 10, 20 and 30 minutes.
Data presented as mean ± SEM. n=12 for all 3 sessions. * indicates a significant between group (p ≤
0.001). † indicates significant within group difference compared to baseline (p ≤ 0.05).
48
49
5.06
5.31
5.25
5.82
5.35
5.94
6.80
6.34
8.50
8.50
7.39
3
4
5
6
7
8
9
10
11
12
5.90 ± 0.38
7.04
8.09
8.09
6.04
6.47
5.66
5.09
5.54
32.00 ± 0.93
33.93
27.88
29.20
38.05
29.23
29.61
34.23
35.50
28.53
34.63
31.18
32.00
Con
11.02 ± 0.68
9.66
13.55
7.19
8.65
12.02
11.02
13.40
8.37
10.57
12.22
15.09
10.47
Ecc
3-5 minutes
35.36 ± 0.90
35.72
35.36
32.71
41.14
31.23
33.06
37.54
38.75
30.82
38.12
34.52
35.36
Con
11.32 ± 0.65
9.86
14.51
9.95
7.65
10.22
11.32
15.56
9.37
10.50
13.05
12.28
11.63
Ecc
8-10 minutes
36.05 ± 1.32
36.94
31.19
33.97
42.77
31.83
35.49
40.00
40.58
33.01
39.96
39.01
27.78
Con
11.22 ± 0.69
9.83
15.46
11.55
7.15
9.45
11.22
15.11
9.39
10.84
11.17
13.00
10.43
Ecc
18-20 minutes
Individual VO2 data and group mean ± SEM. Data collected over a 2 minute period and presented as an average.
SEM
6.20 ± 0.40
4.87
5.12
2
Mean ±
3.85
4.05
1
4.99
Ecc
Baseline
Con
Subject
36.61 ± 1.41
37.42
30.86
34.68
44.01
32.44
35.59
41.55
41.29
32.80
40.85
39.26
28.60
Con
10.83 ± 0.62
9.24
14.49
9.70
7.74
9.89
10.83
14.60
8.16
10.84
11.17
12.03
11.31
Ecc
28-30 minutes
Table 2.4: Oxygen consumption (mL.kg.min-1) during a single 30 minute bout of equivalent load concentric or eccentric cycling
2.3.7 Heart rate
As expected the heart rate response (Figure 2.10) is very similar to the oxygen
consumption response (Figure 2.9). Individual data can be seen in Table 2.5. When
subjects rested at baseline there was no difference in resting heart rate (Con: 87 ± 4
beats.min-1, Ecc: 88 ± 6 beats.min-1). Upon commencing exercise there was an increase
in heart rate in both groups however only the concentric mode increased significantly
(Con:147 ± 3.7 beats.min-1, Ecc: 101 ± 5 beats.min-1). Over the 10, 20 and 30 minute
time points the concentric heart rates continued to climb by a further 14 beats where the
eccentric heart rates remained stable within 2 beats.min-1. The final heart rates at 30
minutes were 175 ± 4 beats.min-1and 107 ± 5 beats.min-1 for concentric and eccentric
respectively. Figure 2.10 shows that there is a significant cardiovascular drift present in
the concentric condition but not in the eccentric condition (p<0.05). Figure 2.10 also
shows that at no exercising time point is heart rate significantly higher than at rest for
the eccentric group.
50
Figure 2.10: Heart rate throughout a 30 minute bout of concentric  or eccentric  cycling at 60%
of peak concentric workloads. Data recorded at baseline, 5, 10, 20 and 30 minutes. Data presented
as mean ± SEM. n=12 for all data points. * indicates a significant between group difference (p ≤
0.001). † indicates significant within group difference compared to baseline (p ≤ 0.05) and ††
indicates within group difference compared to † (p ≤ 0.05).
51
52
92
66
99
95
84
81
63
87
99
4
5
6
7
8
9
10
11
12
88 ± 5
81
88
61
86
88
90
113
58
88
147 ± 4
167
140
148
140
158
159
162
124
145
131
149
141
Con
101 ± 5
107
103
75
92
123
111
122
67
89
96
117
110
Ecc
3-5 minutes
Individual heart rate data and group mean ± SEM
SEM
87 ± 4
85
3
Mean ±
107
106
2
96
97
Ecc
92
Con
Baseline
1
Subject
161 ± 4
178
150
157
156
170
175
168
129
165
147
158
174
Con
104 ± 5
110
110
85
93
113
124
129
68
93
99
113
116
Ecc
8-10 minutes
170 ± 4
186
158
164
166
177
181
175
138
179
165
163
186
Con
106 ± 5
107
114
94
93
109
132
127
67
106
92
113
116
Ecc
18-20 minutes
Table 2.5: Heart rate during a single 30 minute bout of equivalent load concentric or eccentric cycling
175 ± 4
189
160
167
172
185
185
181
140
184
174
167
192
Con
107 ± 5
110
119
88
101
110
123
130
64
111
92
113
116
Ecc
28-30 minutes
2.3.8 Muscle Activation
Surface EMG is used to determine the amount of neural signal responsible for a muscle
contraction. Individual data can be seen in Table 2.6 and group means in Figure 2.11.
In the pre fatigue exercising sample, the concentric muscle activation analysed by root
mean squared was 0.042 ± 0.003 for the concentric group and0.038 ± 0.003 for the
eccentric group. The eccentric group remained slightly lower at the 10 and 20-minute
collection periods with final values of 0.043 ± 0.003and 0.039 ± 0.004 for concentric
and eccentric respectively at the 30-minute time point. Although the eccentric group had
slightly lower muscle activation at every time point it was not significant. Two subjects
had poor adhesion with electrodes once sweating and electrodes fell off. Ten of the
twelve subjects had viable muscle activation data.
Figure 2.11: Total quadriceps muscle activity measured by electromyography. Values presented as
the sum of the activity of rectus femoris, vastus medialis and vastus lateralis muscles for concentric
 or eccentric  cycling. Data recorded at 5, 10, 20 and 30 minutes and presented as mean ± SEM.
n=8 for concentric and 9 for eccentric.
53
54
0.054
0.035
0.031
0.040
0.037
0.041
0.062
0.039
0.029
0.039 ±
0.004
0.037
0.046
0.039
0.037
0.057
0.042
0.038
0.035
0.043 ±
0.003
4
5
6
0.042 ±
0.003
0.059
0.046
0.043
0.055
0.030
0.042
0.038
0.032
0.047
0.027
Con
0.038 ±
0.003
0.022
0.042
0.058
0.038
0.038
0.039
0.027
0.029
0.049
0.037
Ecc
3-5 minutes
Individual muscle activation data and group mean ± SEM
Mean ±
SEM
12
11
9
8
7
3
1
0.067
Ecc
0.025
Con
Baseline
0.033
Subject
0.040 ±
0.003
0.033
0.047
0.041
0.055
0.033
0.035
0.041
0.034
0.054
0.030
Con
0.039 ±
0.004
0.024
0.051
0.059
0.038
0.039
0.042
0.025
0.035
0.051
0.022
Ecc
8-10 minutes
0.042 ±
0.003
0.032
0.040
0.046
0.053
0.035
0.037
0.044
0.035
0.063
0.032
Con
0.040 ±
0.004
0.027
0.043
0.060
0.044
0.043
0.045
0.030
0.037
0.051
0.023
Ecc
18-20 minutes
Table 2.6: Muscle activation during a single 30 minute bout of equivalent load concentric or eccentric cycling
0.043 ±
0.003
0.035
0.038
0.042
0.057
0.037
0.039
0.046
0.037
0.067
0.033
Con
0.039 ±
0.004
0.029
0.039
0.062
0.041
0.037
0.040
0.031
0.035
0.054
0.025
Ecc
28-30 minutes
2.4 Discussion
This study has been the first study to simultaneously collect cardiovascular, metabolic
and neuromuscular variables throughout an extended 30 minute bout of low load
eccentric cycling.
Lower cardiovascular and metabolic demand has been well
established for exercise bouts of much shorter duration (Abbott & Bigland, 1953;
Abbott et al., 1952; Bigland-Ritchie et al., 1973; Dufour et al., 2007; Perrey et al.,
2001) and much higher intensity (Dufour et al., 2004; Walsh et al., 2001), however was
not known for an extended bout at a lower intensity. This is an important piece of
information, as the current ACSM guidelines for exercise is 30 minutes or greater of
moderate intensity exercise on five or more days per week, or 20 minutes or greater of
vigorous intensity exercise (Garber et al., 2011). The first study of this project has
confirmed that the lower metabolic and cardiovascular response, evident in short
duration and high intensity bouts of eccentric exercise, is similar for extended low
intensity bouts. This indicates that eccentric exercise at these low absolute loads of
60% of concentric peak can be tolerated for an extended period of time.
During 30 minutes of low load eccentric cycling the oxygen cost was 34%, 32%, 31%
and 30% that of the concentric group at 5, 10, 20 and 30 minutes for equal absolute
power outputs. This was the expected result and has previously been demonstrated for
shorter duration bouts, and bouts of greater power output (Perrey et al., 2001, Dufour et
al., 2006). The data from this study adds to the overall picture by demonstrating that
the reduced oxygen cost during eccentric cycle ergometry is consistent over a period up
to 30-minutes. If anything, the data suggests a trend towards the difference between
concentric and eccentric oxygen consumption increasing as the session continues. He et
al. (2000) found that ATP is consumed twice as much during concentric compared to
isometric muscle contractions.
Additionally, ATP utilisation is lower in eccentric
contractions compared to isometric contractions. Rychson et al. (1997) did not entirely
support this finding, but instead found that there is decreasing efficiency from isometric
to eccentric to concentric contraction and proposed that the differences were due to
differences in the actin-myosin-ATP stoichiometry. The efficiency was quantified for
concentric contractions to be 15 % versus 35 % for eccentric contractions. Although
there are discrepancies in the literature in relation to the relative cost of isometric
contractions, the important implication for this project, that is consistently reported in
55
the literature is that eccentric contractions use less ATP than concentric contractions.
Although not measured in this study, the mechanism for the reduced oxygen
consumption during eccentric contractions is believed to be due to the mechanical
detachment of some of the actin and myosin filaments (McHugh et al., 1999). The well
established cross-bridge muscle contraction theory proposes that during concentric
muscle contractions, 1 molecule of ATP is required to detach the acto-myosin bond.
This mechanical detachment of some of the actin and myosin bonds that occurs during
eccentric contractions, instead of the ATP dependant detachment in concentric
contractions spares 1 ATP per bond and this is responsible for the reduced oxygen
consumption seen during eccentric contractions (McHugh et al., 1999).
Similar to oxygen consumption heart rate in the eccentric group elicited only 69%, 65%,
62% and 61% of the concentric heart rate at the 5, 10, 20 and 30 minute time points
compared to the concentric group. Metabolic demand is the primary factor responsible
for adjustments in cardiac output during exercise, so it is logical that there is a similar
pattern between oxygen consumption and heart rate, however there is also evidence to
suggest involvement of non-metabolic factors related to muscle tension and or activity
(Dufour et al., 2007). Dufour et al., (2007) had 1 group perform heavy eccentric cycle
ergometry and 2 groups perform either light or heavy concentric cycle ergometry. The
heavy eccentric group performed 270W of eccentric work, and the heavy concentric
group performed 270W of concentric work. The light concentric group was matched to
the heavy eccentric group for oxygen consumption and performed 70W of concentric
exercise. The results of this study showed that the heart rate and cardiac output in the
heavy eccentric group were higher than the light concentric group despite equal energy
expenditure. This highlights that non-metabolic factors play a smaller yet significant
role in the cardiac output and heart rate response during concentric and eccentric
cycling ergometry. The mechanisms of this non metabolic contribution remain to be
established.
Differences in the heart rate response between metabolically equal concentric and
eccentric exercises may be attributed to differences in total heat production and
thermoregulation. During concentric and eccentric muscle contractions matched for
oxygen consumption, total heat production is almost triple in eccentric contractions
56
compared to concentric contractions (Nielsen et al., 1972). This is attributable to the
energy, in this case from the motorised ergometer, being lost during deceleration and
transferred as heat into the resisting muscles. Despite total heat production being higher
during eccentric exercise, internal temperature is significantly lower at any level of total
heat production (Nadel et al., 1972; Nielsen, 1966; Nielsen, 1969). Additionally muscle
and skin temperature is significantly higher during eccentric exercise compared to
concentric exercise (Nadel et al., 1972; Nielsen, 1966; Nielsen, 1969). Exercising
muscle blood flow is determined by the metabolic requirement of the working muscles
and not the necessity to dissipate heat (Nadel et al., 1972). When metabolic heat
production is equal, blood flow is equal, resulting in the additional non metabolic heat
during eccentric contractions having no additional capacity to be removed by the blood
and istherefore absorbed by the muscles resulting in greater elevations in muscle
temperature causing increased skin blood flow and therefore a lower core temperature
(Nadel et al., 1972; Nielsen, 1966; Nielsen, 1969).
Interestingly, there was no cardiovascular drift present in the eccentric group that
appeared to be present in the concentric group. Cardiovascular drift is an increase in
heart rate beyond the metabolic requirement during exercise and is largely attributed to
a redistribution of blood flow to cutaneous vascular beds in order to dissipate heat
produced by increased metabolism in exercise (Rowell, 1986). An increase in core
temperature also leads to a redistribution of blood to cutaneous vascular beds in order to
dissipate heat (Nielsen et al., 1972; Rowell, 1986). This study did not measure core or
skin temperature but there are two factors that need consideration. Firstly differences in
heat production between concentric and eccentric contractions and secondly differences
in metabolic heat production at different exercise intensities.
As there is cardiovascular drift in the concentric data, this suggests that the total heat
production being greater than the metabolic heat production (Nielsen, 1966). The
mechanism of this additional transfer is unknown but it seems logical to assume it is
associated with additional friction due to the mechanical detachment of actin and
myosin bonds.
In this study, the oxygen consumption is vastly different so the
contribution of metabolic heat production will play a large role in differences in total
heat production between groups. Metabolic energy is converted to mechanical and
57
thermal energy in human skeletal muscle. This is quiet inefficient with between 2070% of the total energy produced being released as heat (González-Alonso, 2012).
Although not measured the absence of cardiovascular drift during eccentric cycling
group that was clear in concentric cycling group is hypothesised to be due to a greater
total heat production during concentric cycling.
Despite eccentric contractions
producing more non metabolic heat, the contribution of metabolic heat plays a larger
role in this case.
This is promising information as it demonstrates that at these
workloads the metabolic and cardiovascular strain will remain lower for eccentric cycle
ergometry and will become relatively even lower as session duration progresses towards
30-minutes..
Muscle activation during 30 minutes of eccentric cycling in the current project was not
significantly different to the concentric control at any of the exercising time points.
This finding is contrary to several studies that have demonstrated significantly lower
muscle activation for eccentric cycle ergometry when compared to equivalent force
concentric cycle ergometry (Dufour, et al., 2007; Perrey, et al., 2001).
Muscle
activation for all four time points was slightly but not significantly lower than the
concentric control. The failure to see significantly lower muscle activation for the
eccentric group is unknown and contrary to the literature. It could be that the stimulus
at these low loads is not high enough for the differences to appear. Dufour et al. (2007)
had subjects performing eccentric and concentric work at 270W which is 36% more
than the force produced in the current project. Perrey et al. performed the comparisons
at 330W almost twice that of the current study. The differences between the high force
muscle activation comparisons in the literature and not seen in the low force
comparisons in this project lead to the hypothesis that differences in muscle activation
do not become apparent until a higher threshold of force production. All eccentric
EMG measurements were lower than the concentric control. It is well known that there
is a linear relationship between isometric muscle tension and muscle activation in
human muscle (Lippold, 1952), and it has been shown that lower limb extensors display
better linearity than upper limb muscles (Weir et al., 1992). It has been demonstrated
that concentric and eccentric muscle contractions also possess linearity with muscle
force and muscle activation, however the activation to torque relationship is
significantly weaker in eccentric contractions (Babault et al., 2001). The data from
58
Babault (2001) showed that at lower relative torques of approximately 20-30% of peak
isometric force, isometric, concentric and eccentric muscle activation is similar. As the
relative contraction force increases eccentric muscle activation separates to lower levels
than the isometric and concentric contractions due to the significantly lower slope. This
provides a probable cause for the absence of a difference in muscle activation between
concentric and eccentric cycle ergometry in the current study that is seen at higher
forces (Dufour et al., 2007; Perrey et al., 2001; Bigland-Ritchie et al, 1976).Two
subjects muscle activation data had to be excluded due to erroneous data. The large
number of contractions and dynamic nature of the cycling protocols made it more
difficult for the electrodes to maintain adherence.
This data demonstrates two favourable benefits of eccentric cycling over equal load
concentric cycling. Firstly heart rate and oxygen consumption is lower during the early
minutes of exercise and remain lower over a thirty minute period. Secondly, there is no
cardiovascular drift during eccentric cycling as is seen in equal load concentric cycling.
This means that as exercise duration increases, the work required from the heart will
increase for concentric cycling but remains stable for eccentric cycling.
The
combination of these two attributes suggest that low load eccentric cycling may be a
superior training modality to concentric cycling as it places less work on the heart for
equal external work produced. This could be particularly viable training modality for
individuals with low exercise tolerance.
Throughout the eccentric cycling literature there is a common theme that in order to
become accustomed to the unusual technique of eccentric cycling that specific
familiarisation sessions are required. Previous studies (Dufour et al., 2007; Dufour et
al., 2004; Perrey et al., 2001) have performed 3-4 familiarisation sessions and have used
a reduction in muscle soreness as an indicator of successful familiarisation, or not
justified the number of sessions at all. In these three eccentric cycling papers the
absence of muscle soreness proceeding the sessions has been used as an indicator of
successful familiarisation however no qualitative power output data has been collected
or reported. The three identifiable short comings of these studies are a lack of reporting
power output data, a lack of reporting the variability of power output and the
assumption that the absence of muscle soreness indicates adequate familiarisation. The
59
SRM power crank system has allowed this study to be the first to collect precise power
output data every session throughout the familiarisation sessions to more accurately
investigate the familiarisation process. The current study used second by second force
data to confirm that the desired workload has actually been achieved. This study shows
that there was an initial undershoot with an average of only 82% of the target workload
being achieved. This increased to 95% of the target workload in the second session and
by the third session the desired workload was within 1% of the target. This mean power
output data is important as it confirms that after 3 familiarisation sessions a group of
young healthy male and female subjects are able to perform eccentric cycling at a
desired workload. It is important however to also consider the variability of the work
performed as an average alone will not illustrate any large fluctuations in the work
performed. There has been no mention in any of the studies on the variability of the
work performed in the familiarisation period. The current study has used standard
deviation of the second by second force data as well as the coefficient of variation
(C.V.) as two separate measures of variability. Both methods have shown a systematic
decrease in the variability over three familiarisation sessions. It was not known if this
systematic improvement in variability would continue to decrease beyond three
sessions. Finally, the current study has shown a poor relationship between muscle
soreness and mean work performed (r2 = 0.1917) and also between muscle soreness and
the variability of work (r2 = 0.1582) in a healthy young cohort over 3 sessions. This
poor correlation between muscle soreness and work performed and work variability
demonstrate that the disappearance of muscle soreness is not an adequate indicator of
successful and raises the question that if the absence of muscle soreness is the only
factor used in the previous studies to determine successful familiarisation, how
consistently was the work actually being performed? The use of the SRM powercrank
system during for familiarisation is a much more rigorous method for monitoring the
familiarisation process during eccentric cycling.
2.4.1 Concluding Comments
This study has confirmed that eccentric cycling at low absolute loads will consistently
induce lower metabolic and cardiovascular stress than concentric cycling, with no
difference between groups for muscle activation over a duration up to 30-minutes. This
confirms that the attributes of eccentric cycling appear to be a particularly suitable
60
training modality for individuals with low exercise tolerance as equivalent force and
muscle activation can be produced for less cardiovascular and metabolic strain. The
proceeding study will perform a training program using eccentric cycling equivalent
low loads and determine whether health benefits are achieved.
61
Chapter 3: Training Study
3.1 Introduction
It is known that using single bout eccentric cycling at matched absolute workloads,
heart rate is significantly lowered (Dufour et al, 2006; Dufour et al., 2004; Perrey et al.,
2001; Abbot et al., 1952; Asmussen, 1952; Bigland-Ritchie et al., 1976) and the
metabolic oxygen requirement is reduced (Abbott et al., 1952).
Study one has
demonstrated that the reduced metabolic and cardiovascular stress observed in short
duration bouts of less than 10 minutes is maintained over a 30 minute period.
Alternatively when workloads are matched based on metabolic or cardiovascular
demands, eccentric cycling can be performed at much greater workloads, up to 450W
(Dufour et al, 2006; Dufour et al., 2004; Perrey et al., 2001). On the basis of this large
force producing capacity, eccentric cycling has been utilised as a training tool during
short term exercise interventions. Consistently, it has been demonstrated to increase
direct measures of lower limb muscle strength in young healthy adults (LaStayo et al.,
2000; LaStayo et al., 1999), elderly cohorts (LaStayo et al., 2003; Mueller et al., 2009)
and in individuals with cardiovascular conditions (Steiner et al., 2004). The
underpinning mechanism for these positive outcomes is clearly based upon the high
loads achieved in the studies, often in excess of 400W (LaStayo et al., 1999; Lastayo et
al., 2000). To the best of our knowledge, there is no reported data that confers whether
direct physiological strength gain can be achieved during an eccentric cycling
intervention that maintians a very low cardiovascular reponse. This would be most
applicable for pathology groups that have little or no chance of increasing heart rate or
demonstrate severe exercise intollerance. Preliminary reports indicate that this is worth
pursuing. A recent study using five males with severe COPD (Rocha Viera et al., 2011)
highlights that high absolute workloads are not achievable. The group employed a five
week eccentric cycling training intervention that demonstrated severe intolerenace to the
intial stimulus whereby the mean workload of 10 W was achieved by the patient group.
However, most encouragingly the patients were then able to increase worloads to
146W over a 5 week period. The results from Roch Viera et al., (2011) study appear
positive as there was a 7 fold increase in the workload performed on the bike, yet this is
an indirect measure of strength. Coupled with a low subject number, no control group,
and no direct isometric strength measurement reported, limits the interpretation of this
work. One can infer that muscle strength gain can be achieved during eccentric cycling
62
while eleciting a minimal increase in cardiovascular reponse above resting conditions.
However it is difficult to quantify this without a direct measure of strength either in an
isolated action or a functional movement. Therefore study two aimed to determine if
eight weeks of very low demanding eccentric cycling traning would increase lower limb
strength compared to a tradtional concentric cycling control group.
63
3.2 Methods
3.2.1 Equipment
3.2.1.1 Custom built eccentric ergometer
The eccentric training sessions were performed on the custom cycle ergometer as
described in section 2.2.1.
3.2.1.2 Concentric cycle ergometer
In an attempt to reduce the chance of mechanical issues with the custom ergometer, as it
had never been used so frequently, a separate recumbent cycle was used for the
concentric training sessions (Lode BV Excalibur Sport VI.52, Groningen, Netherlands).
Figure 3.1: Concentric recumbent cycle ergometer
64
3.2.2 Subjects
Twenty four sedentary male subjects with a mean age of 42.7 participated in the study.
Twenty four subjects were chosen as an adequate number as it was large enough to
show significant differences in the heart rate and oxygen consumption measurements in
study one. It is also larger than the subject numbers used by similar eccentric training
studies that have demonstrated significant improvements in strength. Recruitment was
advertised via campus wide emails. Subjects were required to be sedentary males
between the ages of 30 - 55 with no injuries or medical conditions that could be
aggravated exercise.
3.2.2.1 Screening
All subjects filled out a subject screening form (Appendix B) and a modified Physical
Activity Assessment Tool (Appendix C) based off a validated tool (Meriwether et al.,
2006).
Subjects then had an informal interview with the primary researcher and
applicants deemed to be regularly physically active were excluded. Written consent
was obtained prior to participation, and all protocols were approved by the University of
Wollongong Human Research Ethics Committee (HE10/010).
3.2.3 Experimental Standardisation
Subjects were required to refrain from strenuous exercise and consumption of alcohol
for the 12 hours prior to each trial. Subjects were also instructed to avoid caffeine and
tobacco for the 2 hours prior to all testing or training sessions. Additionally to these
restrictions subjects were required to refrain from eating or drinking for 3 hours prior to
the resting ECG.
65
3.2.4 Experimental Design
After subjects were screened and deemed suitable to participate in the study all subjects
performed baseline testing. Baseline testing consisted of resting ECG, resting blood
pressure, peak workload test, isometric strength and functional strength testing.
Subjects were matched for baseline isometric strength and allocated randomly into
either a concentric or eccentric training group. The eccentric group performed five, 10
minute familiarisation sessions prior to beginning the eight week training regimen.
Subjects in both groups performed an 8-week program performing 2 sessions per week.
Progressive overload was applied through increasing training session duration from an
initial 10-minutes per session to 30-minutes per session by the end of the program.
Specific session durations can be seen in Table 3.1. All sessions were monitored by the
tester and heart rate and RPE data collected throughout each session.
Functional
strength, resting and peak cardiovascular tests were re-tested 3 days after the final
training session. Isometric strength was tested at 2 week intervals throughout the
program and muscle activation was tested during baseline, week 5 and final testing
sessions. Figure 3.1 illustrates the study design.
66
Recruitment through
campus email
Screening and
baseline testing
Group 1
Concentric
Group 2
Eccentric
Subjects matched and paired based on
peak isometric strength then randomly
allocated into either the concentric or
eccentric training groups
8 week
training
intervention
8 week
training
intervention
Final testing
Final testing
Figure 3.2: Study design
67
5 Familiarisation
sessions
3.2.5 Baseline Data
3.2.5.1 Anthropometric Data
A single tester, experienced in anthropometric measurements completed all
measurements to reduce the risk of variability between testers. The following baseline
anthropometric measurements were taken:
3.2.5.1.1 Height
Height of each subject was measured using a wall mounted stadiometer (Model 222,
Seca, Birmingham, UK) with the subject barefoot and placed into the Frankfort plane.
3.2.5.1.2 Body Mass
Body mass was measured using calibrated, electronic scales. Subjects were barefoot and
wore minimal clothing (Seca, Birmingham, UK).
3.2.5.1.3 Girth Measurements
Three girth measurements were taken using an Lufkin W606PM anthropometric tape
(Cooper Tools, Apex, NC, USA). Measurements were taken 3 times and the median
value was used.
Gluteal- subject standing with feet together. Circumference taken from the side
at the widest point of the gluteal muscles.
Umbilicus- subject standing and required to breathe normal. Circumference was
taken at the umbilicus at the end of expiration.
Mid thigh- Subjects standing with feet shoulder width apart. Circumference was
taken at the midpoint between the anterior superior iliac spine and the base of the
patella.
3.2.5.2 Resting Data
3.2.5.2.1 Resting Electrocardiogram
Subjects were required to rest supine for 20 minutes prior to the collection of a 5 minute
ECG strip using a Norav ECG system (Norav Medical Inc, Delray Beach, FL, 33445,
USA). For the 5 minute ECG subjects were required to breath at a comfortable depth,
in time with a metronome set to 12 breathes per minute. This ECG was used to calculate
resting heart rate and power spectrum frequency analysis. The power spectrum bands
68
looked at, low frequency (LF), high frequency (HF) and total power. Resting heart rate
was determined by calculating the mean R-R interval over the entire 5 minutes period.
3.2.5.2.2 Resting Blood Pressure
Resting blood pressure was measured after 25 minutes of supine rest, on the right arm
using an automatic oscillometric device (OMRON, DVM-Medical Supplies, Canberra,
Australia).
3.2.6 Peak Workload Test
All subjects performed an incremental max workload test. Baseline samples were
collected during 5 minutes of seated rest. A 5-minute warm up was performed at 50 W.
Following the 5-minute warm up, the workload began to increase at a rate of 50 W.min1
, at a set cadence of 60 rpm until volitional exhaustion.
3.2.6.1 Measurements during peak workload test
3.2.6.1.1 Metabolism
Expired gas samples were collected continuously from the beginning of the rest period
until the end of the protocol. The samples were used to determine oxygen consumption
and carbon dioxide production via a respiratory gas analysis system (TrueOne 2400
metabolic measurement system, ParvoMedics Inc., Utah, USA).
This data was
collected in a mixing chamber mode and sampled second by second. The data was
presented as averages in 15-second increments. The gas analysers were calibrated
before each trial using alpha gas standards (15.97% oxygen, 4.03% carbon dioxide,
balance Nitrogen). The system was calibrated for volume using a syringe of known
volume (3 L) and was calibrated over 5 flow rates ranging from 50 L.min-1 – 500 L.min1
.
3.2.6.1.2 Heart Rate
Heart rate data was obtained from ventricular depolarisation , using a heart rate monitor
(Polar Electro Sport Tester, Finland) and displayed and collected with the TrueOne
2400 metabolic measurement system. Data was averaged into 15 second samples to
correspond with the metabolic data.
69
3.2.6.1.3 Perceived exertion
Perceived exertion ratings (RPE) were obtained during exercise every minute, using the
15 point Borg Category Scale (Borg, 1962) and participants were asked the question:
“How hard are you exercising?”
The 15-point Borg Category scale
6
7
Very, very light
8
9
Very light
10
11
Fairly light
12
13
Somewhat hard
14
15
Hard
16
17
Very Hard
18
19
Very, very hard
20
Figure 3.3: The BORG category scale. Used to quantify an individual’s perception of physical
exertion.
70
3.2.7 Isometric Strength
Maximal isometric quadriceps muscle strength was recorded as maximal isometric knee
extension force (N) exerted at 90 degrees knee joint flexion using a custom built 1000N
load cell (Applied Measurement, X-TRAN, 51W-1kN, Eastwood, NSW, Australia) via
a DC pressure amplifier (Neurolog, 108A, DigitimerNeurolog, Hertfordshire, UK).
Joint position was standardised, by keeping hip and knee at 90o of flexion using the
lateral femoral epicondyle as the axis, the greater trochanter and the lateral malleolus.
The lever arm was fixed 2 cm above the lateral malleolus using a nonstretch static
Velcro strap (Aagaard et al., 2001). The back support was set at 90 degrees and subjects
were secured using femoral, pelvic and thoracic straps (Dvir, 2004). After a 10 minute
warm up on a concentric cycle ergometer and 10 warm-up contractions, increasing to
maximum effort, subjects performed 3 maximal contractions. The contractions were
initiated by a 3-second increase in force production toward maximum, followed by a 3second period holding maximum voluntary contraction (Hunter et al., 2006). If the
variation between attempts was too great, more contractions were performed until a
minimum of two attempts achieve peak value within +/-5% of each other. Sampling
rates for the load cell were set to a frequency of 1000 Hz. The maximum voluntary
contraction was recorded as the highest peak torque achieved of the 3 attempts and was
calculated as torque. To calculate torque the lever distance from the knee joint axis to
the load cell anchor was measured and torque data is presented as N.m-1.
Figure 3.4: Isometric strength testing apparatus. Subject sitting in strength testing apparatus with
femoral, pelvic and chest straps.
71
3.2.8 Electromyography (EMG)
Surface Electromyography (EMG) was recorded using bipolar Ag-Agcl adhesive cloth
electrodes with a surface diameter of 15mm (red dot, 3M, Ryde, Australia). EMG
signals were pre amplified with a low frequency cut off to 3 Hz, amplified 1000 times
(Neurolog 844, 820, 144, 135, DigitimerNeurolog, Hertfordshire, U.K). The signal was
filtered with a high pass range of 500 Hz and low pass range of 10 Hz via the Power
1401 analogue to digital converter (Cambridge Electronic Design, Cambridge, U.K.).
Data was collected for each channel at 1000 Hz.
The muscles measured were rectus
femoris, vastuslateralis and vastusmedialis using the same preparation and electrode
placement as outlined above in section 2.1.7.1, and was collected at a frequency of 1000
Hz. The maximum voluntary contraction will be recorded as the highest peak torque
achieved of the 3 attempts. Spike software will be used to analyse peak torque and
EMG was measured over a 100 ms time period, 50 ms either side of peak torque. The
vastuslateralis electrode was placed two thirds of the distance between the greater
trochanter and the base of the patella with an interelectrode spacer of 2 cm. The
electrodes were on an oblique angle just lateral to the midline. The vastusmedialis
electrode was placed 2 cm medial to the superior rim of the patella. Electrodes were set
at an oblique angle of 55 degrees with 2 cm spacing. Subjects had electrode positions
marked with ink and measured from known anatomical landmarks to ensure
reproducibility. Data was analysed for Root Mean Squared (RMS) using Spike
software. Program scripts were written to minimise error.
3.2.9 Functional Strength
Functional strength was measured using a 6 repetition maximum protocol on a 45o,
plate loaded leg press (Cybex International, Medway, MA, USA). The leg press
machine was adjusted accordingly so the hips and back were well supported and the hip
and knee positions were at 90 degrees, using the lateral femoral condyle as the axis at
the knee and the greater trochanter at the hip. Subjects were cued to cross their arms
across their chest throughout the exercise and to breathe out upon exertion. Subjects
performed an initial warm up set with minimal load. From this warm up set, an estimate
was made to determine the mass of the first attempt. Subjects were rested for 3 minutes
between each attempt and there was no more than six attempts performed in any one
testing session to prevent the accumulative effect of fatigue.
72
Figure 3.5: 45 degree leg press. Subject can be seen sitting in the leg press machine
With the sled at lowest position and the knee at 90 degrees.
3.2.10 Familiarisation
Subject familiarisation followed the same procedures as outlined in section 2.1.6,
however for this study, subjects performed 5 sessions as opposed to 3. As was seen in
the results from Chapter 2 there was a systematic decrease in the variability over 3
sessions. An additional 2 sessions allowed us to see if this pattern continued or if there
was a plateau in the variability of work.
3.2.10.1 Measurements during familiarisation
3.2.10.1.1 Power, cadence and heart rate
Power cadence and heart rate data were recorded as outlined above in section 2.1.5.1.1.
3.2.10.1.2 Muscle Soreness
Muscle soreness was measured 5 minutes, 24 hours, 48 hours and 72 hours after
training using a visual analogue scale as described in section 2.2.6.1
3.2.11 Training Intervention
After initial testing was complete, subjects were matched in pairs according to their
initial isometric strength. From there, each pair was split and were randomly allocated
to either group 1 (Concentric) or group 2 (Eccentric) for the 8-week training
intervention. The training intensity for each group was set at 60% of the peak workload
achieved in the peak aerobic test during baseline testing. Both groups completed 2
73
sessions per week, starting at 10 minutes per session and progressively increasing to 30
minutes (Table 3.1).
Group 1 cycled on a recumbent cycle where workload was fixed at 60% of their peak
workload. Subjects were required to maintain a cadence of 60 rpm. Heart rate was
recorded every minute using a polar monitor. Ratings of perceived exertion were
collected every 2 minutes using a 15 point BORG scale.
Group 2 had a fixed cadence of 60rpm controlled by the custom built cycle ergometer
but were required to use biofeedback to maintain the target of 60% peak workload.
Heart rate and ratings of perceived exertion were collected as in group 1 as well as
power (W) and cadence (rpm) which was recorded second by second via the SRM
power crank system. SRM details can be seen in section 2.2.1.4.
Table 3.1: Training Session Timeline
Week
Number of
Sessions
1
2
3
4
5
6
7
8
2
2
2
2
2
2
2
2
10
15
20
20
25
25
30
30
20
30
40
40
50
50
60
60
Session
Duration
(minutes)
Week total
(minutes)
Weekly session information
3.2.12 Training Impulse (TRIMP)
The training impulse (TRIMP) is a common method used to quantify the aerobic work
of exercise training (Banister & Calvert, 1980; Banister et al., 1992; Iwasaki et al.,
2003). It uses session duration, average session heart rate and different exponent values
for males and females which weights TRIMP for relatively higher exercise intensities.
The following formula was first used by Banister et al. (1980) and was used to calculate
TRIMP in this study.
74
𝑇𝑅𝐼𝑀𝑃 = 𝑡𝑟𝑎𝑖𝑛𝑖𝑛𝑔 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛 (𝑚𝑖𝑛𝑢𝑡𝑒𝑠)
∗ [(𝐻𝑅𝑎𝑣𝑔 – 𝐻𝑅𝑟𝑒𝑠𝑡)/(𝐻𝑅𝑚𝑎𝑥 – 𝐻𝑅𝑟𝑒𝑠𝑡)]
∗ 𝑓𝑎𝑐𝑡𝑜𝑟 𝐴 𝑒𝑥𝑝[(𝐻𝑅𝑎𝑣𝑔 – 𝐻𝑅𝑟𝑒𝑠𝑡)/(𝐻𝑅𝑚𝑎𝑥 – 𝐻𝑅𝑟𝑒𝑠𝑡) ∗ 1.92]
HRavg : mean heart rate throughout training session
HRrest :resting heart rate
HRmax:maximal heart rate
Factor A = 0.64 for males, 0.86 for females
Factor B = 1.92 for males, 1.67 for females
3.2.13Final Testing
Subjects returned between 3 and 5 days after their training final session for the final,
testing. Peak workload, isometric strength, functional strength and resting tests were
repeated as outlined in baseline testing section above.
3.2.14 Statistical Analysis
Subject characteristic data age, height, mass and BMI reported as mean ± SD. All other
experimental data reported as mean ± SEM. Where only baseline and final testing
sessions occurred two tailed paired T tests were performed to determine significant
within group changes (p ≤ 0.05). For between group analysis at baseline or final testing
unpaired T tests were used to determine between group differences (p ≤ 0.05). Where
more than two testing sessions occurred a one way repeated-measures ANOVA was
used to determine within group differences (p ≤ 0.05). A two way ANOVA was used to
determine a group difference independent of session.
Linear regressions were
performed to determine the correlation between muscle soreness and power output and
muscle soreness and power output variability.
75
3.3 Results
Of the 24 subjects that commenced the study, 17 completed the entire 8 week
intervention and final testing sessions. Two subjects withdrew with musculoskeletal
injuries unrelated to the study, one withdrew for medical reasons and four withdrew due
to work or family commitments. The drop outs occurred at various time points between
the initial testing session and the fourth week of the intervention. Of the 17 subjects
that completed the intervention 8 were in the concentric group and 9 were in the
eccentric group.
3.3.2 Physical Characteristics
At the beginning of the study, the concentric and eccentric groups had a mean age of 46
± 8 and 40 ± 8 years respectively. There was no significant difference between groups
at baseline with height, mass and BMI scores of 1.79 ± 0.07 m, 94.3 ± 15.9 kg and 29.4
± 5.6 respectively for the concentric group and 1.80 ± 0.07 m, 90.6 ± 15.6 kg and 27.9 ±
5.1 for the eccentric group. There were no significant changes in any of these variables
for either group at final testing. Individual and group mean, age, height, mass and BMI
data are reported in Table 3.2. Anthropometric measurements of waist, hip and thigh
displayed no significant between group difference at baseline or final testing, nor was
there any within group changes over the duration of the training program. The waist to
hip ratio was used along with BMI as a surrogate indicator of conditioning low physical
fitness. Anthropometric data can be seen in Table 3.3.
76
77
Eccentric mean ± SEM
Concentric mean ± SEM
E9
E8
E7
E6
E5
E4
E3
E2
E1
C8
C7
C6
C5
C4
C3
C2
C1
Subject
40 ± 8
46 ± 8
31
36
36
45
53
52
35
34
39
30
50
47
47
46
38
53
1.80 ± 0.07
1.79 ± 0.07
1.78
1.79
1.81
1.89
1.83
1.81
1.71
1.92
1.7
1.74
1.89
1.76
1.74
1.87
1.84
1.81
1.69
Baseline
Baseline
54
Height (cm)
Age (years)
Table 3.2: Physical characteristics
90.6 ± 15.6
94.3 ± 15.9
66.7
107.6
75.4
103.6
86.5
95.1
73.8
98.4
108.2
86.2
110.8
84.0
116.6
103
79.3
72.5
102.1
Baseline
90.2 ± 16.3
94.9 ± 16.0
65.9
109.1
76.0
101.0
86.8
94.0
71.0
98.0
110.2
89.0
110.8
84.1
117.7
103.5
79.9
72.3
102.1
Final
Mass (kg)
27.9 ± 5.1
29.4 ± 5.6
21.2
33.7
23.1
29.1
25.8
29.0
25.3
26.7
37.4
28.4
30.9
27.1
38.5
29.4
23.4
22.0
35.6
Baseline
BMI
27.8 ± 5.4
29.8 ± 5.7
20.9
34.2
23.3
28.4
25.9
28.7
24.4
26.6
38
29.3
30.9
27.1
38.8
31
23.6
22
35.6
Final
78
101.0
88.7
110.4
123.6
99.8
118.5
102.4
128.4
92.0
83.0
100.0
96.9
108.0
88.3
116.4
82.6
107.8 ± 11.8
99.5 ± 15.6
C2
C3
C4
C5
C6
C7
C8
E1
E2
E3
E4
E5
E6
E7
E8
E9
Concentric mean ± SEM
Eccentric mean ± SEM
99.4 ±13.8
106.7 ± 11.3
83.5
115.5
99.0
100.4
95.2
99.5
83.0
93.0
125.5
102.5
114.5
98.2
123.0
111.4
88.0
101.2
115.0
Final
106.0 ± 9.0
109.4 ± 12.1
92.6
117.0
98.6
103.5
106.4
107.0
98.5
110.5
120.3
106.3
117.5
105.6
123.3
117.0
98.5
87.7
119.0
Baseline
93.5
117.0
99.0
107.2
105.0
107.0
98.0
110.0
119.0
106.0
116.0
104.1
123.2
113.0
100.0
87.7
119.0
Final
106.2 ± 8.5
108.6 ± 11.5
Hip (cm)
Individual anthropometric data with group mean ± SEM in the bottom two rows.
118.0
Baseline
Waist (cm)
C1
Subject
Table 3.3: Anthropometric measurements
58.1 ± 6.0
59.1 ± 5.0
51.0
65.4
53.4
61.5
57.0
55.4
52.4
58.3
68.4
59.0
60.6
56.0
67.2
59.3
57.8
50.0
63.0
Baseline
58.2 ± 5.8
59.2 ± 5.4
51.5
64.9
53.5
61.2
57.8
55.4
52.5
58.3
68.5
59.2
62.8
54.5
0.93 ±0.08
0.99 ±0.07
0.89
0.99
0.90
1.04
0.91
0.93
0.84
0.83
1.07
0.96
1.01
0.95
1.00
0.94
57.5
67.5
0.90
1.15
0.99
0.93 ± 0.07
0.99 ± 0.08
0.89
0.99
1.00
0.94
0.91
0.93
0.85
0.85
1.05
0.97
0.99
0.94
1.00
0.99
0.88
1.15
0.97
Final
W/H ratio
Baseline
57.9
50.5
63.4
Final
Thigh (cm)
3.3.3 Resting cardiovascular measurements.
There is a strong association between resting heart rate (Perret-Guillaume et al., 2009)
and blood pressure (Pescatellio et al., 2004) with health and mortality. A decrease in
any of these measurements that could be attributed to the training intervention would
indicate potential cardiovascular health benefits associated with this programme. At
baseline there was no significant difference in resting heart rate between groups (Con:
64 ± 2 beats.min-1, Ecc: 71 ± 4 beats.min-1). By final testing there was a 1 beat (63 ± 2)
reduction in the concentric group and a significant 9 beat (62 ± 3) reduction in the
eccentric group. This greater reduction achieved by the eccentric group brought both
groups closer together so at final testing there was only a 1 beat difference between
groups.
At baseline, resting systolic blood pressure was 132 ± 2 mm.Hg-1 for the
concentric group, and 125 ± 4 mm.Hg-1 for the eccentric group. At final testing there
had been a 2 mm.Hg-1 reduction achieved in both groups (Con: 130 ± 3 mm.Hg-1, Ecc:
123 ± 5 mm.Hg-1) however this was not significant. Resting diastolic blood pressure
was not significantly different between groups at baseline (Con: 83 ± 2 mm.Hg-1, Ecc:
74 ± 4 mm.Hg-1). Neither group achieved a significant decrease by final testing (Con:
80 ± 2 mm.Hg-1, Ecc: 72 ± 3 mm.Hg-1). Group data for resting heart rate, systolic blood
pressure and diastolic blood pressure can be seen in Figures 3.5 A, B and C.
respectively. Individual baseline and final data can be seen in Table 3.4.
79
Figure 3.6: Resting cardiovascular parameters. Resting (A) heart rate, (B) systolic blood pressure
and (C) diastolic blood pressure for concentric  (n=8) and eccentric  (n=9) training groups.
Data presented as mean ± SEM. ϯ indicates within group difference compared to baseline (P ≤ 0.05)
80
81
55
62
60
58
67
74
69
70
74
83
75
45
73
78
70
67
64 ± 2
71 ± 4
C2
C3
C4
C5
C6
C7
C8
E1
E2
E3
E4
E5
E6
E7
E8
E9
Concentric mean ± SEM
Eccentric mean ± SEM
62 ± 3
63 ± 2
64
66
57
71
43
68
60
69
58
73
60
70
60
61
62
53
61
Final
125 ± 4
132 ± 2
110
134
114
131
111
146
112
134
134
126
128
140
132
138
127
125
142
Baseline
123 ± 5
130 ± 3
104
136
116
125
114
146
103
133
132
132
129
131
143
137
120
122
128
Final
Systolic blood pressure (mm.Hg)
Individual resting cardiovascular data with group mean ± SEM in the bottom two rows.
67
Baseline
Resting Heart Rate (beats.min-1)
C1
Subject
Table 3.4: Resting cardiovascular measurements
74 ± 4
83 ± 2
60
86
64
78
65
87
68
70
88
78
76
90
88
88
76
80
84
Baseline
72 ± 3
80 ± 2
55
83
67
76
65
81
64
74
83
76
83
86
88
82
71
72
81
Final
Diastolic blood pressure (mm.Hg)
3.3.4 Indices of autonomic activity
Heart rate variability is used as an indicator of autonomic tone. Activity measured in
the low frequency band represents the sympathetic and parasympathetic contribution of
heart rate control where the high frequency band indicates the parasympathetic
contribution. The low frequency to high frequency ratio is used to determine the
relative contribution of sympathetic and parasympathetic modulation of heart rate. A
shift in the LF:HF ratio can be used to demonstrate a shift towards a more dominant
contribution from sympathetic or parasympathetic nervous system. Baseline and final
heart rate variability data can be seen in Table 3.5. There was no significant between
group difference for any of the frequency domain measurements at any time point nor
was there and within group changes that could be contributed to the training
intervention.
82
83
139
88
106
81
100
125
57
80
176
102
59
61
113
227
169
146
101 ± 9
126 ± 19
C2
C3
C4
C5
C6
C7
C8
E1
E2
E3
E4
E5
E6
E7
E8
E9
Concentric mean ± SEM
Eccentric mean ± SEM
103 ± 14
104 ± 17
142
119
83
185
84
116
89
57
52
121
79
195
141
93
59
48
98
Final
177 ± 18
159 ± 28
157
243
114
233
193
127
110
179
237
125
131
22
195
225
150
139
286
Baseline
146 ± 19
153 ± 25
159
196
222
207
113
50
101
162
105
145
170
25
166
116
135
194
273
Final
High Frequency(ms2)
558 ± 36
537 ± 23
517
574
659
540
309
635
658
594
534
542
604
645
450
519
545
475
517
Baseline
513 ± 31
539 ± 17
540
540
432
563
325
588
563
615
454
614
569
584
0.79 ± 0.17
1.12 ± 0.51
0.93
0.70
2.00
0.48
0.31
0.46
0.93
0.98
0.34
0.46
0.95
4.65
0.41
0.47
516
506
0.59
1.00
0.40
Baseline
0.84 ± 0.20
1.46 ± 0.90
0.89
0.61
0.37
0.90
0.75
2.3
0.88
0.35
0.50
0.83
0.46
7.70
0.85
0.80
0.44
0.25
0.36
Final
HF:LF ratio
530
462
533
Final
Total Power (ms2)
Individual maximal data and and group mean ± SEM. * represents significant between group difference compared to baseline.
† represents a significant within group difference (P<0.05).
115
Baseline
Low Frequency (ms2)
C1
Subject
Table 3.5: Heart rate variability
3.3.5 Peak Aerobic Cycle Test
At baseline a significant difference was observed in peak concentric and eccentric
power outputs of 262.5 ± 18.6W and 300.6 ± 15.4W respectively.
There was a
significant increase in the concentric group peak workload by final testing to 301.9 ±
10.7 W that was not present in the eccentric group 302 8 ± 14.9. There was a
concomitant, significant increase in the concentric group’s peak oxygen consumption
from 27.4 ± 2.1 mL.kg.min-1to30.0 ± 1.7 mL.kg.min-1. Eccentric group peak oxygen
consumption remained the same from 33.2 ± 1.5 mL.kg.min-1 at baseline and 33.3 ± 1.6
mL.kg.min-1 at final testing. This close relationship between peak work load and peak
oxygen consumption was expected. Additionally there was no significant change in
peak heart rate for either group that was also expected. Individual and group mean peak
aerobic workload, oxygen consumption and heart rate can be seen in Table 3.6 and
group means can be seen in Figure 3.6.
84
Figure 3.7: Peak aerobic (A) workload, (B) O2 consumption and (C) heart rate for concentric 
(n=8) and eccentric  (n=9) training groups. Data presented as mean ± SEM. ϯ indicates within
group difference compared to baseline (P ≤ 0.05). * indicates between group difference at baseline.
85
86
260
300
250
285
150
305
310
265
395
270
280
285
350
295
315
250
262.5 ± 18.6
300.6 ± 15.4*
C2
C3
C4
C5
C6
C7
C8
E1
E2
E3
E4
E5
E6
E7
E8
E9
Concentric mean ± SEM
Eccentric mean ± SEM
235
315
280
350
290
290
340
370
255
340
330
275
305
300
330
280
255
Final
33.2 ± 1.5 *
27.4 ± 2.1
36
29.7
38.7
32.3
33.4
29.8
33.4
39.9
26
35.6
24.9
23.6
20.8
24.7
35.5
31.3
22.8
Baseline
33.3 ± 1.6
30.0 ± 1.7 †
35.7
29.2
35.3
33.4
32.3
30.2
37.5
41.2
24.8
35.1
27.5
26.9
25.8
28.2
37.4
34.5
24.6
Final
Peak VO2 (mL.kg.min-1)
171 ± 4.7
165.4 ± 6.3
163
184
186
173
148
162
182
185
157
179
173
177
164
128
184
158
161
Baseline
171.4 ± 3.9
165.9 ± 5.6
164
178
183
179
155
166
182
182
155
185
163
175
158
138
184
171
154
Final
Peak heart rate (beats.min-1)
* represents significant between group difference compared to baseline. † represents a
302.8 ± 14.9
301.9 ± 10.7 †
Individual maximal data and and group mean ± SEM.
significant within group difference (P<0.05).
240
Baseline
Peak Workload (W)
C1
Subject
Table 3.6: Peak aerobic cycle test data
3.3.6 Familiarisation
3.3.6.1 Power output
Subjects performed five, 10-minute familiarisation sessions at 60% of the peak
workload achieved in the maximal exercise test. The mean target power output for the
familiarisation sessions was 180.1 ± 9.3W. The first session indicated that subjects were
undershooting the target power output with an actual mean power output of 138.2 ±
13.0W, 41.9(W) lower than the target. The second session had increased to 171.2 ± 10.0
(W) by the third session the 182.5W was achieved. The fourth and final session
remained consistent around the target workload at 192.1 ± 9.5 and 183.4 ± 9.8 W.
Individual data can be seen in Table 3.7 and group data can be seen in Figure 3.7A.
3.3.6.2 Variability of power output
During the initial familiarisation session there was considerable variability in the power
output during sessions of 51.6 ± 4.2 W. The variability systematically decreased over
the five familiarisation sessions. Values were 51.6 ± 4.2 W, 41.7 ± 6.0 W, 41.6 ± 3.3 W,
36.4 ± 3.1 W and 28.5 ± 2.8 W from the first through to the fifth session respectively.
Additionally there was a significant reduction in variability from the first to the fifth
session. Individual data can be seen in Table 3.7 and group data can be seen in Figure
3.7B.
87
Figure 3.8: Eccentric power output during familiarisation sessions. Percentage of target power
output (A), and standard deviation of power output (B) throughout 10 minute familiarisation
sessions one (F1), two (F2), three (F3), four (F4) and five (F5). Data presented as mean ± SEM. n=9
for all three sessions. ϯ indicates p ≤ 0.05
88
89
47
87
87
98
97
77
78
3
4
5
6
7
8
9
95 ± 4
99
101
98
101
75
92
113
88
90
F2
102 ± 6
117
82
137
104
83
92
112
91
101
F3
70
51
41
56
61
31
41
63
109
105
100
100
92
103
89
120
52 ± 6
50
102
102 ± 3
F1
F5
42 ± 4
86
27
27
43
38
37
31
41
45
F2
42 ± 3
48
38
40
42
35
38
38
65
32
F3
(W)
36 ± 3
42
46
22
39
43
46
29
36
24
F4
38
28
13
35
28
28
23
37
23
F5
†
28 ± 3
Standard deviation of power output
Variability of power output
0.05
0.41 ±
0.55
0.28
0.18
0.3
0.38
0.28
0.66
0.49
0.54
F1
0.05
0.26 ±
0.59
0.14
0.16
0.2
0.3
0.24
0.17
0.2
0.31
F2
0.02
0.23 ±
0.28
0.25
0.16
0.19
0.24
0.25
0.21
0.3
0.2
F3
0.02
0.19 ±
0.23
0.26
0.12
0.16
0.25
0.26
0.16
0.15
0.14
F4
Coefficient of Variation
* represents significant between group difference compared to baseline. † represents a significant
107 ± 3 †
127
92
106
116
103
104
111
101
106
F4
Individual familiarisation data and mean ± SEM.
within group difference (P<0.05).
SEM
77 ± 6
61
2
Mean ±
58
F1
1
Subject
(% of target)
Precision of power output
Table: 3.7: Work performed and variability of work during familiarisation
0.01
0.15 ±
0.22
0.17
0.07
0.18
0.16
0.17
0.14
0.14
0.14
F5
3.3.6.3 Muscle Soreness
Muscle soreness was present 5 minutes after the first session, peaked at 24 hours, and
systematically decreased beyond 24 hours for the first three familiarisation sessions.
Muscle soreness peaked at 5 mins, dropped at 24 hours and was absent at 48 and 72
hours for the fourth and fifth sessions. The magnitude of muscle soreness for all four
time periods systematically decreased from the first to the fifth session with the
exception of the 5 minute point in the fifth session. This was the same pattern as was
illustrated in the 3 familiarisation sessions in study 1, however the magnitude in this
subject cohort was much lower. The magnitude of muscle soreness for all four time
periods systematically decreased from the first to the fifth session with the exception of
the 5 minute point in the fifth session. Muscle soreness for the 5-minute time point was
significantly lower in the last three sessions compared to the first. Eight of the nine
subjects in the eccentric group returned all VAS data sheets.
Individual muscle
soreness data can be seen in Table 3.8 and group data in Figure 3.8.
Figure 3.9: Muscle soreness following familiarisation sessions. Muscle soreness measured using a
Visual Analogue Scale (VAS) for sessions one (F1), two (F2), three (F3), four (F4) and five (F5).
Data presented as mean ± SEM. n=8 for all three sessions. * indicates p ≤ 0.01. † indicates p ≤ 0.05
90
Table 3.8: Muscle soreness after familiarisation sessions
Muscle soreness (%)
Time
Subject
F2
F3
F4
F5
1
6
5.5
0.5
1
3.5
2
1
0.5
0
0
0
3
9
11
3.5
3.5
1
4
0
0
0
0
0
5
9
0
0
0
0
6
0.5
0.5
0
0
1.5
7
3
3.5
1
0
0
8
1
0
0
0
0
1
1
11
4
2
0
2
0
0
0
0
0
3
33
27.5
2.5
0.5
0.5
4
0
0
0
0
0
5
21
1
1.5
0
0
6
0
0
0
0
0
7
13
7.5
1.5
0
0
8
0.5
0
0
0
0
1
0
8
0
0
0
2
0
0
0
0
0
3
39.5
8.5
4
0
0
4
0
0
0
0
0
5
10
0
0
0
0
6
0
0
0
0
0
7
3.5
4
1
0
0
8
0
0
0
0
0
1
0
1
0
0
0
2
0
0
0
0
0
3
19.5
3
1
0
0
4
0
0
0
0
0
5
2
0
0
0
0
6
0
0
0
0
0
7
0
0
0
0
0
8
0
0
0
0
0
5 min post mean ± SEM
4±1
3±1
1±0
1±0
1±0
24 hr post mean ± SEM
9±4
6±3
1±1
0±0
0±0
48 hr post mean ± SEM
7±5
3±1
1±0
0±0
0±0
72 hr post mean ± SEM
3±1
2±0
0±0
0±0
0±0
72 hours after session
48 hours after session
24 hours after session
5 minutes after session
F1
Individual muscle soreness data calculated as a percentage. Mean ± SEM presented in the lower
four rows for each time period and session.
91
3.3.6.4 Using muscle soreness as an indicator of familiarisation
Similar to the results of study 1, the results of study 2 demonstrate a weak relationship
between muscle soreness and both measures of work performance. A linear regression
between muscle soreness and percentage of target power output (Figure 3.9A) resulted
in an R2 = 0.0637 and a correlation between muscle soreness and work variability
(Figure 3.9B) resulted in an R2 = 0.018. This poor relationship raises the question that if
the absence of muscle soreness was used as an indication of successful familiarisation in
other studies, how confident can the researcher’s be that the desired amount of work
was actually performed. Eight subjects had complete data sets for muscle soreness,
work performed and work variability were used for the linear regressions.
92
Figure 3.10: The lack of linearity between (A) mean power output, (B) power output variability and
muscle soreness 24 hours after familiarisation sessions one, two, three, four and five.. n = 8 for all 3
sessions in graph A and B.
93
3.3.7 Training Session Data
3.3.7.1 Work performed
All training sessions were visually monitored and digital biofeedback given to the
subject via the SRM system. One training session from each of the different training
durations was recorded. Subjects were blinded to the recorded session. Mean data
shows subjects performed the training sessions within 7.2 ± 3.3, 3.4 ± 9.0, 5.5 ± 2.6, 2.7
± 1.5 and 3 ± 1.8 % of target workload for the 10,15,20,25 and 30 minute sessions
respectively.
Figure 3.11: Mean power output during eccentric training sessions. Subjects were visually
monitored by the tester for all sessions and were provided with verbal feedback when required.
Additionally, subjects were randomly audited at one session at each different exercise duration.
Subjects were blinded to the recorded session. Data presented as mean ± SEM. n=9 for all five
exercise durations. The dashed line represents the target workload of 180 W.
94
3.3.7.2 Training heart rates
The average heart rates over the 16 training sessions were 154 beats.min-1 and 95
beats.min-1 for concentric and eccentric groups respectively. As a percentage of heart
rate reserve this equates to 89% for the concentric group and 24% for the eccentric
group. Two-way analysis of variance showed a significant difference for heart rate
between the concentric and eccentric groups (p< 0.001). Individual data can be seen in
Table 3.9 and group data in Figure 3.11. In relative terms, the eccentric group was
training at a heart rate intensity 38 % lower than the concentric group. There was no
session effect present for either group.
3.3.7.3 Training ratings of perceived exertion
The average rating of perceived exertion over the 16 training sessions were 15for
concentric and 10 eccentric groups respectively. The terms that these numbers best
relate to are “Hard” for the concentric group and “Very Light” for the eccentric group.
One way analysis of variance showed the groups to be significantly different (p ≤
0.001). This pattern matches the heart rate data and shows that the subjects in the
eccentric group perceived their training intensity to be 36 % easier than the concentric
group. Individual data can be seen in Table 3.9 and group data in Figure 3.12.
3.3.7.4 Training Impulse (TRIMP)
The TRIMP method is used as a method for quantifying training load. It uses heart rate
and session duration however is weighted for exercise intensity. Individual weekly
TRIMP values can be seen in Table 3.10. Total TRIMP for the entire 16 sessions is a
4431 (au) for concentric and 254 (au) for the eccentric group. This means that over the
entire 8–week program the eccentric group performed only 6% of the aerobic work of
the concentric group.
95
Figure 3.12: Mean heart rate data over the 16 training sessions for the concentric  (n=8) and
eccentric  (n=9) training groups. Data recorded as mean ± SEM. * indicates a significant
between group difference at all training sessions (p ≤ 0.001).
96
Figure 3.13: Mean ratings of perceived exertion data over the 16 training sessions for the
concentric  (n=8) and eccentric  (n=9) training groups. Data recorded as mean ± SEM. *
indicates a significant between group difference at all training sessions (p ≤ 0.01).
97
98
154 ± 5
152 ± 4
153 ± 4
14
15
16
95 ± 0.8*
92 ± 3
91 ± 3
91 ± 3
93 ± 3
95 ± 4
92 ± 4
93 ± 2
94 ± 4
91 ± 3
95 ± 4
97 ± 4
96 ± 4
100 ± 3
100 ± 4
94 ± 4
101 ± 5
Eccentric
89 ± 0.5
88 ± 3
87 ± 3
89 ± 3
91 ± 3
90 ± 3
90 ± 2
90 ± 2
89 ± 2
88 ± 3
91 ± 3
91 ± 3
89 ± 3
88 ± 3
89 ± 2
85 ± 2
84 ± 2
Concentric
24 ± 0.9*
21 ± 3
20 ± 3
21 ± 3
23 ± 4
24 ± 4
21 ± 4
22 ± 3
24 ± 4
21 ± 2
28 ± 3
26 ± 4
26 ± 4
29 ± 4
30 ± 4
24 ± 4
31 ± 5
Eccentric
% Heart Rate Reserve (%)
Training session data with group mean ± SEM in the bottom two rows.
SEM
154 ± 0.5
155 ± 4
13
Eccentric mean ±
155 ± 5
153 ± 5
8
12
155 ± 4
7
156 ± 5
156 ± 5
6
11
154 ± 6
5
155 ± 5
153 ± 5
4
10
155 ± 6
3
154 ± 5
150 ± 5
2
9
150 ± 6
Concentric
1
Session
Heart Rate (beats.min-1)
Table 3.9: Training session data
14.9 ± 0.1
14.3 ± 0.2
14.2 ± 0.2
14.8 ± 0.4
14.8 ± 0.4
14.4 ± 0.3
14.9 ± 0.5
14.7± 0.5
15.0 ± 0.5
15.0 ± 0.5
15.0 ± 0.4
15.3 ± 0.4
15.0 ± 0.6
15.0 ± 0.6
14.8 ± 0.5
15.0 ± 0.5
15.4 ± 0.5
Concentric
9.5 ± 0.1*
8.6 ± 0.7
8.9 ± 0.8
9.0 ± 0.8
9.4 ± 0.8
9.1 ± 0.8
9.1 ± 0.8
9.3 ± 0.9
9.3 ± 0.8
9.4 ± 0.8
9.6 ± 0.8
9.4 ± 0.8
0.1± 0.0*
0.0 ± 0.0
2.5 ± 1.1
2.6 ± 0.2
0.0 ± 0.0
0.1 ± 0.1
0.1 ± 0.1
0.1 ± 0.1
0.2 ± 0.1
0.1 ± 0.1
0.0 ± 0.0
0.0 ± 0.0
0.1 ± 0.1
0.0 ± 0.0
0.2 ± 0.2
0.0 ± 0.0
0.1 ± 0.1
0.0 ± 0.0
0.0 ± 0.0
Eccentric
2.1 ± 1.1
3.0 ± 0.6
4.0 ± 0.8
2.8 ± 0.9
2.5 ± 1.2
2.8 ± 0.9
2.4 ± 0.7
2.3 ± 0.6
3.4 ± 0.7
3.0 ± 0.7
3.3 ± 0.8
2.1 ± 0.6
10.1 ± 1
10.0 ± 0.8
3.0 ± 0.9
0.6 ± 0.3
1.0 ± 0.5
Concentric
Rest (minutes)
9.9 ± 0.9
10.1 ± 0.9
10.9 ± 0.9
Eccentric
RPE (BORG category scale)
99
2.6
24.2 ± 1.5
1.9 ± 0.3
0.9
0.2
1.6
17.4 ± 0.8
1.1 ± 0.3
E7
E8
E9
Concentric mean ± SEM
Eccentric mean ± SEM
1.4
2.7
2.2
3.1
2.1
0.0
2.4
0.4
2.2
E6
0.8
E1
26.0
1.9
19.3
C8
32.9
E5
21.8
C7
23.7
2.1
16.9
C6
21.4
E4
15.8
C5
25.0
0.1
19.1
C4
25.3
E3
16.1
C3
20.2
0.4
15.5
C2
19.0
Week 2
E2
15.1
Week 1
C1
Subject
Table 3.10: Training Impulse (TRIMP)
1.9 ± 0.4
31.0 ± 2.2
1.1
1.8
3.6
2.0
4.1
1.2
0.1
0.9
2.4
29.6
45.4
31.3
28.4
28.0
31.3
28.6
25.4
Week 3
1.5 ± 0.3
31.3 ± 2.0
1.1
1.0
2.6
2.0
2.9
1.5
0.1
0.7
1.6
32.8
43.0
33.3
27.6
24.1
32.6
27.7
29.7
Week 4
1.9 ± 0.4
38.9 ± 2.0
1.8
2.0
1.4
3.2
3.1
1.3
0.0
1.0
3.3
41.2
51.3
39.5
35.8
35.0
39.9
33.2
35.1
Week 5
Training Impulse
1.9 ± 0.5
38.5 ± 2.1
1.2
2.1
1.1
5.2
3.3
0.9
0.1
1.6
1.7
36.2
51.7
40.3
2.1 ± 0.5
46.5 ± 2.9
1.7
1.2
1.7
3.4
4.0
1.7
0.0
1.1
3.9
48.9
63.7
47.6
43.8
36.8
33.0
38.1
49.3
42.1
39.5
Week 7
39.7
32.3
36.4
Week 6
1.8 ± 0.4
49.1 ± 3.6
1.6
1.7
1.9
3.1
3.8
1.7
0.0
0.8
1.4
51.4
67.8
55.5
46.8
34.4
53.1
43.3
40.7
Week 8
3.3.8 Maximal voluntary contraction
3.3.8.1 Peak Torque
All subject’s individual testing data can be seen in Table 3.11. Figure 3.13 displays
group changes in peak torque throughout the intervention for concentric and eccentric
groups. During baseline testing there was no significant difference between the groups
peak torque (Con: 1345 ± 158 N.m-1 ;Ecc: 1239 ± 103 N.m-1) (p=0.60). The eccentric
group was tested again after familiarisation and there was no significant difference from
baseline. By the third week of training both groups had increased peak force (Con:1432
± 146 N.m-1, Ecc: 1359 ± 87 N.m-1) and this increase continued systematically until
week 7. The eccentric training group had significantly improved strength by the third
week of training and had significantly increased from the third week value by final
testing (1500 ± 102 N.m-1). The concentric group had significantly increased peak
torque by week 7 of the intervention (1550 ± 106 N.m-1), however there was a slight
decrease in the final testing session (1543 ± 139 N.m-1) and was no longer significantly
different to baseline. The concentric training group achieved a significant improvement
in isometric strength after a total of 230 minutes of training. The eccentric group
achieved a significant improvement in isometric strength after 80 minutes of training.
This includes the additional 30 minutes performed during familiarisation.
100
Figure 3.14: Peak isometric torque values over the 5 testing sessionsfor concentric  (n=8) and
eccentric  (n=9) training groups. Data presented as mean ± SEM. ϯ indicates within group
difference compared to baseline (P ≤ 0.05).
101
Table 3.11 Individual peak Torque (N.m-1)
Subject
Baseline
Week 3
Week 5
Week 7
Final
C1
1351
1047
1405
1355
1276
C2
722
913
922
993
953
C3
1608
1730
1666
1518
1680
C4
1292
1416
1371
1548
1542
C5
1702
1644
1677
1663
1732
C6
627
949
1212
1550
1138
C7
1744
1915
1974
2027
2032
C8
1717
1843
2032
1746
1988
E1
1119
1229
1279
1383
1413
E2
1367
1443
1505
1516
1713
E3
607
806
697
799
855
E4
1097
1483
1527
1456
1550
E5
1109
1300
1349
1510
1409
E6
1464
1447
1408
1541
1652
E7
1301
1289
1305
1349
1378
E8
1716
1776
1952
2025
1981
E9
1368
1453
1648
1530
1547
Concentric
Mean ± SEM
1345 ± 158
1432 ± 146
1532 ± 134
1550 ± 106†
1543 ± 139
Eccentric
Mean ± SEM
1239 ± 103
1358 ± 87 †
1408 ± 113†
1457 ± 105†
1500 ± 102†
Individual peak force data and group mean ± SEM
102
3.3.8.2 Muscle activation
Muscle activation was similar between groups in the baseline isometric strength test.
There was no significant difference between concentric and eccentric peak muscle
activation at baseline, week five or the final testing session. There was also no
significant within group difference for the concentric or eccentric groups over the three
testing sessions. Mean values can be seen in Figure 3.14 and individual data in Table
3.12.
Figure 3.15: Peak quadriceps activation over the 3 testing sessions for concentric  (n=8) and
eccentric  (n=9) training groups. Data presented as mean ± SEM.
103
104
0.158
0.114
0.026
0.247
0.127
0.063
0.046
0.118
0.117
0.047
0.074
0.071
0.084
0.106
0.129
0.242
0.168
0.122
0.104 ±0.024
0.116 ± 0.020
C2
C3
C4
C5
C6
C7
C8
E1
E2
E3
E4
E5
E6
E7
E8
E9
Concentric± SEM
Eccentric± SEM
0.106 ± 0.019
0.097 ± 0.015
0.199
Error
0.093
0.114
0.043
0.08
0.049
0.138
0.117
0.062
0.051
0.137
0.15
0.041
0.084
0.085
C1
Muscle Activity
(RMS)
Baseline
(RMS)
Muscle Activity
Subject
Table 3.12 Muscle activation
Week 5
-0.1 ± 0.1
0.1 ± 0.1
-0.1
-0.1
-0.2
Error
-0.1
0.4
-0.4
0.1
0
0.2
0
0.3
-0.2
0.1
-0.4
0.6
0
Change from BL
(%)
0.101 ± 0.014
0.112 ± 0.016
0.114
0.192
0.123
0.082
0.095
0.091
0.088
0.1
0.027
0.112
0.111
0.047
0.054
0.156
0.165
0.148
0.103
Muscle Activity
(RMS)
Final
-0.1 ± 0.1
0.6 ± 0.6
-0.1
0.1
-0.5
-0.4
-0.1
0.1
0.2
0.4
-0.4
0
-0.1
0
-0.1
0.2
-0.3
4.7
0.2
Change from BL
(%)
3.3.9 Functional Strength
At baseline, the concentric and eccentric groups had a 6 repetition max score of 176 kg
and 192 kg respectively. This was not significantly different between groups. After the
8 weeks of training, the concentric group achieved a 13 % improvement from baseline
to final testing and the eccentric group achieved an 11 % improvement. This was an
absolute improvement of 20.7 kg and 21.1 kg for concentric and eccentric groups
respectively. This was a significant improvement for both groups. Individual data can
be seen in Table 3.13 and group data can be seen in Figure 3.15.
Figure 3.16: Peak functional strength of the lower limb extensors for concentric  (n=8) and
eccentric  (n=9) training groups. Data presented indicates best performance in a 6 repetition
maximum leg press. Data presented as mean ± SEM. ϯ indicates within group difference compared
to baseline (P ≤ 0.05)
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Table 3.13: Functional strength
Baseline (kg)
Subject
150
C1
Final (kg)
165
C2
110
125
C3
250
250
C4
95
110
C5
210
250
C6
145
185
C7
220
250
C8
225
235
E1
175
190
E2
245
250
E3
157.5
165
E4
147.5
170
E5
210
250
E6
220
285
E7
200
200
E8
215
245
E9
160
165
Concentric ± SEM
176 ± 20
196 ± 21
Eccentric ± SEM
192 ± 11
213 ± 15
Individual functional strength data and group mean ± SEM
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3.4 Discussion
This study has achieved a significant improvement in both isometric and functional
strength after an 8-week, low load eccentric cycling protocol. This improvement was
comparable with a concentric control group despite the eccentric group performing
the training sessions with significantly less cardiovascular strain and perceived
effort. This appears to be an efficient mode of strength training as improvements can
be achieved with less cardiovascular strain. This could be a beneficial training
modality for individuals suffering exercise intolerance as it allows improvements in
strength without a large demand for oxygen.
Throughout the intervention the concentric group performed training sessions at an
average heart rate of 154 beats.min-1 compared to the 38% lower 95 beats.min-1 of
the eccentric group. Using the heart rate reserve method the concentric group was
exercising at an average of 89% of HRR which corresponds with “very hard” where
the eccentric group were working at 24% which corresponds with a “light “intensity
(Pollock et al., 1998). Another common tool for quantifying the amount of aerobic
work performed during an activity is the training impulse method (TRIMP). It is
calculated by multiplying the heart rate (beats.min-1) by the session duration
(minutes). Using the TRIMP method over the entire 16 sessions it was calculated
that the eccentric group scored a TRIMP value of 253 where the concentric group
had a TRIMP score of 4431. This common quantitative method demonstrates that
the overall difference in aerobic workload is greater than would appear using heart
rate data alone. Using the current TRIMP scores it suggests that the eccentric group
performed only 6% of the aerobic work as the concentric group. This physiological
data corresponded with psychophysical data collected simultaneously.
Average
perceived exertion of 15 on the BORG scale or “hard” compared to 10 or “very
light” shows that the perception of effort matched the physiological response as seen
from heart rate. An average of 40.8 minutes of rest was taken per subject in the
eccentric group and 1 minute rest per subject for the concentric group over the 8
week program. No subject requested a rest break in the eccentric group due to
fatigue. The rests that were taken by the eccentric group were all due to pain in the
arches of the feet. This problem could potentially be resolved by using a different
pedal system. A racing style pedal was used but perhaps a flatter platform pedal
would be more comfortable. It is clear from the combination of physiological and
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psychophysical data that the subjects in the eccentric group consistently performed
less aerobic work over the 16 training sessions in study 2. The primary aim of this
study was to determine whether strength improvements could be achieved whilst
training at these significantly lower cardiovascular workloads. This data has
confirmed that the training intensity was significantly lower for the eccentric group.
3.4.1 Strength adaptations to low load eccentric cycling
It is well documented that when two training groups perform concentric or eccentric
cycling at equivalent cardiovascular workloads that the group performing eccentric
cycling can do so at much higher forces and achieve greater improvements in
strength (Lastayo et al., 1999, Lastayo et al., 2000, Myer et al., 2003). This study
has shown that 8 weeks of eccentric cycling at loads, much lower than those used by
Lastayo (1999), Lastayo (2000) and Myer (2003) can still produce significant
improvements in isometric and functional strength. The 12.7% and 10.7% increase
in isometric and functional strength respectively was not significantly different to the
14.7% and 13.0% improvements observed in the concentric group. These equivalent
improvements occurred despite the eccentric group training with significantly less
metabolic and cardiovascular strain.
This equivalent improvement in strength,
achieved with lower cardiovascular demand appears to indicate that eccentric cycling
at low load’s, is a more energy efficient method for improving strength in a
sedentary male population.
Isometric strength was measured at baseline and final testing as well as 3
intermediate time points. This allows the improvements in strength to be tracked
throughout the program and has demonstrated an interesting pattern. There was a
significant increase in peak force in the eccentric training group at week 3 testing
where the concentric training group did not achieve a significant improvement in
peak force until week 7 testing. This can be seen in Figure 3.18. This means that the
eccentric training group achieved a significant improvement in strength after only 80
minutes of training.
This includes the additional 30 minutes of familiarisation
performed by the eccentric group. The concentric group performed 230 minutes of
training before a significant improvement was seen.
This means the eccentric
training was able to significantly improve strength in approximately one third of the
time required to improve strength in the concentric control group. The eccentric
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training group systematically increased strength over the five testing sessions where
the concentric group peaked at week 7 and then reduced slightly during the final
testing session. If this pattern was to continue it appears that the eccentric training
group is still improving where the concentric group appears to have plateaued. In
order to determine this, a longer duration training study would need to be performed.
One possible reason for the reduction in peak force for the concentric group in the
final testing session is fatigue. During the final two weeks of training the concentric
group performed 95% more aerobic work as calculated by the TRIMP method. This
additional work may have resulted in fatigue that had a detrimental effect on the final
maximum voluntary contraction. Although it is not possible confirm, this data
indicates the possibility that a longer training period would produce further increases
in isometric strength where the concentric group had already plateaued.
The study with the closest program to the current training study was an 8 week
regimen with healthy male subjects with a mean age of 23.9 (LaStayo et al., 2000).
This study achieved a 26% increase in isometric quadricep strength over the 8
weeks. This means that the 12.5% increase in strength achieved in the current study
is 48% of that achieved by LaStayo et al. (2000). This could be interpreted that the
current regimen is only half as good as the LaStayo et al. (2000) regimen however
the workloads and total volume need to be considered carefully. The high force
eccentric training of the LaStayo study had an average force production of 489 W
and total of 780 minutes over the 8 weeks. The current study had an average force
production of 180 W and a total of 350 minutes. This means that the current study
performed only 45% of the total volume at 36% of the workload. Despite this
contrast in volume and intensity the current study still achieved 48% of the
improvement. This would suggest that in terms of increasing strength, the current
regimen is more energy efficient. Other factors that could affect the response is the
exercise history of the cohorts. The mean age of the subjects in the current training
study are approximately 20 years older than in the two studies by LaStayo et al.
(1999; 2000). There is some evidence to suggest that a high response to strength
training can be achieved in the elderly, with studies reporting an increase of up to
60% in frail elderly subjects. This could suggest that the magnitude of strength
changes are highly dependent upon the responsiveness of the subject cohort used.
The current training study did not perform functional tests such as the sit to stand or
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timed up and go. As the subjects were all living independently it was assumed that
their performance in those types of test would be easily achieved.
There are two generally accepted pathways for increasing skeletal muscle strength,
changes to the nervous system and intrinsic changes to the muscle itself.
Neuromuscular adaptations that can improve strength can be further broken down
into increased activation of agonists (Sale, 1988), decreased activation of antagonists
(Häkkinen et al., 1998) and improved synchronisation of motor unit firing (Sale,
1988).
Intrinsic muscular changes that are capable of increasing strength are
increases in muscle cell cross-sectional area (hypertrophy) or alterations to muscle
architecture such as pennation angle and fascicle length. The only attempt by this
study to determine the mechanism of the achieved strength change was by measuring
muscle activation of the quadriceps using surface EMG. Despite an increase in peak
isometric force in the concentric and eccentric groups, there was no significant
change in muscle activation of the quadriceps femoris. Compared to baseline there
was a 0.1% and -0.1% change in muscle activation at week five for concentric and
eccentric respectively and a 0.6% and -0.1% change at final testing. This absence of
a significant change in agonist muscle activation with a corresponding increase in
muscle strength would suggest that the increase in strength observed was not due to
greater agonist activation by the nervous system. Traditional resistance training
interventions have been demonstrated to significantly increase agonist muscle
activation (Sale, 1988). There are no known studies that have performed high force
eccentric cycling studies and reported changes in agonist muscle activation. High
force eccentric cycling studies that have found strength increases ranging from 33% 60% (LaStayo et al., 2003; LaStayo, et al., 2000; Lastayo et al., 1999) have not
measured or reported muscle activation and have attributed the strength increases to
significant muscle fibre hypertrophy. Eccentric resistance training has been shown
produce greater increases in muscle activation than concentric training (Pesini et al.,
2002), with high force eccentric resistance training demonstrating up to a 7 fold
greater increase in surface EMG compared to concentric training (Hortobagyi et al.,
1996). There is no evidence of an increase in muscle activation in the current study
however it is possible that the low force contractions utilised do not provide enough
stimulus to cause an adaptation of increasing muscle activation. It is generally
accepted that the increases in skeletal muscle strength and power seen in the early
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stages of a resistance training program are attributed to alterations in neuromuscular
factors (Seyness, 2007; Moritani, 1979). Although the EMG data can rule out an
increase in agonist muscle activation being responsible for the strength changes, it
can not rule out the nervous system completely. Synchronisation of motor units or a
decrease in antagonist muscle activation are possibilities but were not measured so
can not be confirmed. In order to test if there has been a decrease in activation of the
antagonist muscles surface EMG of biceps femoris group would need to be
measured. Increased synchronisation can be measured by fine wire EMG of 2
separate motor units simultaneously.
Skeletal muscle cross sectional area is known to be an adaptation to strength training
(Sale et al., 1987) and is directly related to force production (Maughan et al., 1983).
Eccentric resistance training is a particularly potent stimulus for producing
hypertrophy (Hather et al., 1991; Higbie et al., 1996).
The characteristics of
eccentric contractions allow for a greater force production than is possible using
concentric contractions and this produces greater stimulus for hypertrophy (Doss &
Karpovich, 1965; Katz, 1939).
The current project did not measure fibre cross
sectional area so it can not be confirmed whether hypertrophy has occurred. High
force eccentric cycling studies of equivalent length to the current study have
demonstrated increases in skeletal muscle cross sectional area up to 52% in a young
healthy population (LaStayo, et al., 2000) and 60% in the elderly (Lastayo et al.,
2003). It has been demonstrated for both upper limb (Nosaka et al., 02) and lower
limb (Paschalis et al., 05) eccentric exercise that volume rather than intensity is
responsible for the magnitude of muscle damage. Equal volumes of high and low
intensity eccentric exercise elicit the same degree of skeletal muscle damage
(Nosaka et al., 02; Paschalis et al., 05). Despite the low intensity eccentric training
causing similar levels of muscle damage to high intensity, the low intensity training
caused less acute negative effects on muscle performance (Nosaka et al., 02;
Paschalis et al., 05). Therefore, low intensity eccentric exercise will potentially
produce equivalent damage and associated benefits as high force eccentric training,
without the negative effects on recovery and performance. The current eccentric
cycling training program is high very volume and low force. In fact for a 30 minute
session there was 1800 high velocity, low force contractions.
The findings of
Nosaka (2002) and Paschalis (2005) suggests due to a volume rather than intensity
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dependency between eccentric muscle contractions and muscle damage, that similar
muscle damage will have occurred in the current study compared to the high force
eccentric cycling studies in the literature (LaStayo et al., 2003; LaStayo et al., 2000;
Meyer et al., 2003). This provides good evidence that the strength changes found in
this study are likely due to an increase in skeletal muscle cross-sectional area.
The final possibility is alterations in muscle architecture (Blazevich et al., 2007).
Fasicle angle changes occur in a linear fashion over the first few months of training
where fascicle length adapts rapidly and does not continue to change beyond the first
few weeks of training (Butterfield 2006). Studies have shown that increases in
muscle fibre length can occur as early as 10 days and changes in fibre angle as early
as 35 days (Seynnes et al., 2007). The current training study lasted 56 days so it is
possible that the strength improvements seen in this group are associated with one
of, or a combination of these architectural changes. This increase in fascicle length
is caused by the addition of sarcomeres in length and resistance training has been
shown to induce this in both animal (Lynn et al., 1998) and human studies
(Blazevich et al., 2007; Seynnes et al., 2007). Increased fascicle length is known to
be associated with muscle excursion range, maximum shortening velocity and the
force length relationship (Blazevich et al., 2007).
Specifically to this project
Blazevich et al., (2007) and Seynnes et al., (2007) measured these increases in
fascicle length in the quadriceps group, however it has also been shown to occur in
other muscle groups (Potier et al., 2009). There is conflicting theories regarding the
influence of mode of muscle contraction and changes in fascicle length. Potier et al.,
(2009) found that eccentric training increased skeletal muscle fascicle length where
concentric controls did not produce an increase. Blazevich et al., (2007) suggested
changes in fascicle length are not influenced by contraction mode and are most likely
effected by training range of motion. In the current training study, range of motion
was kept consistent via standardised positioning and crank length. This setup was
consistent between the concentric and eccentric ergometers. This would suggest that
because the range of motion is consistent changes in muscle fascicle length between
the groups should be fairly consistent. It was not measured but was noticed by the
researchers that subjects performing eccentric cycle ergometry appeared to drop the
heel more while trying to decelerate the force of the pedals. The concentric group
appeared to plantarflex the ankle slightly more when producing the force to turn the
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pedals. This perceived greater ankle dorsiflexion in the eccentric group resulted in
the knee extending slightly further than the concentric group. It is unknown whether
this small difference in range of motion would have an effect on the adaptations of
muscle fibre length.
This study utilised a concentric control group and did not have a test only control
group.
This makes it difficult to completely disregard any effects of test
familiarisation on improvements in strength. The study design was modelled off
previous studies by LaStayo (1999; 2000) which also used a concentric control
group. These studies however did not find significant improvements in force output
in the concentric group. LaStayo et al. (2000) had a concentric control group that
was tested in a similar fashion, but more frequently at once per week for 10 weeks
and there was no significant improvement seen.
Similarly, LaStayo (1999)
performed weekly isometric strength testing using similar protocols and also found
no significant improvement in strength in the concentric control group. This leads us
to believe that any familiarisation effect in the current study, would be minimal, as a
similar testing protocol was used, for twice as many sessions, and twice as
frequently, but did not significantly improve strength (LaStayo et al., 2000). The
reason for an increase in strength seen in the concentric group in the current study
that is not seen in similar concentric training programs is unknown but thought to be
attributable to differences in the training status and responsiveness in the subject
cohort. Lastayo et al. (1999) used nine healthy subjects, male and female with an
average age of 21.5 years. LaStayo et al. (2000) used 14 healthy male subjects with
an average age of 23.9 years. Both of these cohorts are significantly younger than
the 17 sedentary male subjects that completed the current study.
3.4.2 Cardiovascular adaptations to eccentric exercise
The cardiovascular adaptations achieved in study 2 can be broken into resting
cardiovascular parameters and peak cardiovascular parameters.
When low load
eccentric cycling was repeated over an eight week training study, the amount of
cardiovascular work per session remained significantly less every session over the
duration of the program. This significantly lower cardiovascular response during
eccentric cycling training sessions is particularly positive as it appears to induce
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similar decreases in resting blood pressure and heart rate. Reductions in resting
blood pressure and heart rate are known to have a positive impact on mortality.
The long term adaptation from 8 weeks of low load eccentric cycling, demonstrate
no significant changes in systolic and diastolic blood pressure in the eccentric or
concentric control. Despite the significantly greater cardiovascular demand by the
concentric group, there appeared to be no additional benefit acheived in terms of
resting blood pressure. The eccentric training group had small, but not significant
reductions of 2 mm.Hg-1 in both systolic and diastolic blood pressure and were
comparable to the concentric control group who reduced systolic and diastolic blood
pressure by 2mm.Hg-1 and 3 mm.Hg-1 respectively. Resting heart rate decreased
significantly in the eccentric group only with a 9 beat.min-1 reduction from 71
beats.min-1to 62 beats.min-1. The concentric group achieved a non-significant 1
beat.min-1 reduction from 64 beats.min-1, to 63 beats.min-1. Interpreting this result
needs to be done carefully. The baseline resting heart rate was 7 beats higher in the
eccentric group which could account for the greater reduction seen in that group.
Ideally both groups would have had the same baseline resting heart rate however as
the primary purpose of this project was to determine strength changes, subjects were
matched for baseline isometric strength and not resting heart rate.
Conventional aerobic exercise has been reported to reduce blood pressure and reduce
resting heart rate (Shi et al., 1995).
Strength training has also been shown to
decrease blood pressure in both normotensive healthy adults (Kelley and Kelley
2000, Melo et al., 2008) and in the elderly (Taylor et al., 2003, Melo et al., 2008).
There is no known difference between training with concentric and eccentric muscle
contractions and adaptations in resting heart rate or blood pressure and both modes
of contraction appear to produce positive results. Melo et al. (2008) performed an
eccentric exercise training regimen and demonstrated that high force eccentric
resistance training at 75-80% of peak torque can produce increases in muscular force
production concurrently with a significant decrease in systolic blood pressure. The
forces used in this project are much lower than the forces used by Melo et al. (2008)
but appear to be trending towards similar decreases in blood pressure. As there are
no known differences in adaptations to cardiovascular parameters when looking at
cardiovascular adaptations, the concentric group will be treated as high intensity
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aerobic exercise, and the eccentric group treated as low intensity aerobic exercise.
Cornelisson et al. (2010) compared high and low intensity exercise programs and
although not identical, similarities can be drawn with the current study in terms of
exercise intensity and the length of the intervention. The current study was only 2
weeks shorter than the 10 week Cornelisson et al. (2010) study and the intensities
were close with our concentric group performing sessions at 89% of heart rate
reserve compared to the 66% of the high intensity group in the Cornelisson et al.
(2010) study. The eccentric group performed sessions at 24% of heart rate reserve
compared to the 33% by the low intensity group in Cornelisson et al. (2010). This
demonstrates that in respect to cardiovascular training intensity our concentric group
was higher, and eccentric group lower than the comparison groups in the Cornelisson
et al. (2010) study. Cornelisson et al. found significant improvements for both high
(5mm.Hg-1 reduction) and low intensity (4mm.Hg-1 reduction) training groups for
systolic blood pressure. This is in line with the data from this study however the
magnitude of change is less. This lower magnitude change could be due to the fact
that Cornelisson et al., (2010) performed a 2 week longer intervention, and also
performed 3 hours of exercise per week so the total volume of exercise was much
higher than the current project. The 2mm.Hg-1 decrease in both the concentric (high
CV intensity) and the eccentric (low CV intensity) training groups in this project
does not appear to be affected by the large difference in aerobic training intensity.
Similar decrements were observed for diastolic blood pressure with a 3 and 2
mm.Hg-1 decrease for concentric and eccentric groups respectively. This study was
not designed to determine mechanisms responsible for any changes in cardiovascular
parameters. However mean arterial pressure is the product of cardiac output and
total peripheral resistance so a decrease in mean arterial pressure must be attributable
to a decrease in one or both of these factors. Chronic exercise does not generally
induce a decrease in cardiac output so it can be suggested that changes are due to
decreases in total peripheral resistance (Pescatello et al., 2004).
Resting heart rate data collected in the current study demonstrated no significant
change with a 1 beat.min-1 decrease from 64 to 63 beats.min-1 in the concentric (high
intensity) group and a significant 9 beat reduction from 71 to 62 beats.min-1 in the
eccentric (low intensity) group. This is in contrast to Cornelisson et al., (2010) who
found greater reductions in the high intensity group. It should however be noted that
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although not significantly higher, the baseline resting heart rate of the eccentric
group was 7 beats.min-1 greater than the concentric group, and that by the end of the
8 week program both groups were only separated by 1 beat.min-1. As the primary
objective of this study was to assess changes in strength subjects were matched for
baseline isometric strength and not for resting heart rate resulting in this significant
difference in resting heart rate at baseline. Not too much emphasis can be put on the
differences between groups for this measure but it is safe to say that this data does
not appear to show any greater improvements in the concentric group despite
training under much higher cardiovascular stress.
Where changes in systolic blood pressure appear to be independent of exercise
intensity, reductions in resting heart rate were associated with intensity and a greater
decrease is observed with high intensity training (Cornelisson et al., 2010). There
are three possible mechanisms responsible for a reduction in resting heart rate,
decreased intrinsic cardiac rate, increased parasympathetic nervous system activity
or decreased sympathetic nervous system activity (Katona et al., 1982). There are
conflicting theories surrounding the contribution of these factors in exercise induced
resting bradycardia. Studies using parasympathetic blockades such as atropine have
been able to prove the contribution of reduced intrinsic cardiac rate (Benedito et al.,
1985). The autonomic data collected in this study found no significant change in
low frequency, high frequency or the low frequency: high frequency ratio suggesting
that the reductions in resting heart rate observed in the eccentric group are due to
alterations in the intrinsic cardiac rate.
The current study has shown a significant improvement in peak aerobic power and
peak aerobic workload in the concentric training that was not apparent in the
eccentric group. There was no change in either group for peak heart rate. Endurance
training is known to increase oxygen transport, deliver and use through increased
capillary density, myoglobin concentration and number, size and activity of
mitochondria (Hollonszy and Booth, 1979). There are three proposed possibilities
for the differences in the aerobic adaptations between groups. Firstly it is possible
that the differences seen between groups for peak aerobic power and peak aerobic
workload were due to differences in baseline measures. Although not significant
there was a 38W larger peak aerobic workload, and a 5.8 mL.kg.min-1 larger peak
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aerobic power in the eccentric group at baseline. Secondly it is possible that test
specificity is responsible for the differences.
The incremental step test was
performed concentrically so this would definitely have favoured the concentric
training group. It is however more likely that the higher amount of aerobic work in
the concentric training group is responsible for the greater improvement. It has been
demonstrated that high intensity training has a greater effect on improving peak
aerobic power than lower intensity training (Helgerud et al., 2007; Tabata et al.,
1996). This however is not agreed by all and some studies that have shown high
versus low intensity exercise elicits no difference in peak VO2 (Gaesser & Rich,
1984).
It cannot be definitively concluded from this study but the greater
improvements in peak aerobic workload and peak aerobic power achieved by the
concentric group are believed to be due to higher aerobic workloads during training
combined with test specificity.
Study two extended the number of familiarisation sessions to five to determine
whether the improvements in performance continue to beyond the three sessions
performed in study one. The initial sessions observed a similar pattern to study one
by initial undershooting the target power output in the first session then
systematically increasing up to the target power output by the third session. After
the third session, the power output achieved remained close to the target power
output during the fourth and fifth session.
The power output variability
systematically decreased from the first to the fifth session. The combination of
familiarisation data from Study one and study two suggest that 3 sessions is adequate
to achieve a target power output, however the variability of the power output will
continue to improve out to a minimum of 5 sessions.
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Chapter 4: Clinical Implications
This study has achieved several outcomes that add to the information already known
about eccentric cycle ergometry. The global aim of this project was to begin to
determine whether there is a dose response for the benefits of eccentric cycle
ergometry, particularly in strength gains. As mentioned by Hortobagyi (2003) all of
the eccentric cycle ergometry training studies that have reported strength gains have
utilised high force eccentric cycling at supramaximalconcentric loads.
Study 1
demonstrated that heart rate and metabolic cost remain significantly lower
throughout a 30-minute bout of eccentric cycle ergometry at 60% of concentric peak
workload in a healthy young group of males and females. Previously, all acute
metabolic comparisons had been conducted with much shorter durations, or athigher
absolute workloads. Study 1 provided evidence that eccentric cycle ergometry at sub
maximal concentric workloads can be achieved for significantly lower metabolic and
cardiovascular cost, over a duration recommended for training sessions. Once this
had been established, study 2 used a sedentary male model to represent a cohort with
early possible exercise intolerance and performed an 8-week training intervention.
Despite working at an average of 36% lower heart rate, or 94% lower TRIMP scores,
the eccentric cycling group achieved significant improvements of 21.0% and 10.7%
for isometric and functional strength respectively. These improvements were not
significantly different to the 14.7% and 13.0% improvements seen in the concentric
group, who worked at much higher intensities. As well as the improvements in
strength, there was a significant reduction in the resting heart rate of the eccentric
group that was not apparent in the concentric group and a similar but not significant
decrease in resting blood pressure in both the eccentric and concentric groups. The
clinical implications of this increase in strength and decrease in resting
cardiovascular parameters are an improvement in health risk and mortality.
The 21% increase in isometric strength achieved in this project was statistically
significant, however it is unknown whether this would relate to functional
improvements in daily life. LaStayo et al. (2003) showed that high force eccentric
cycling improved strength, balance, stair descent and timed up and go test results in a
frail elderly population however these improvements occurred simultaneously with a
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60% increase in isometric strength. Improvements in these functional tests resulted
in a shift from “high risk” of falls to “low risk”. While LaStayo et al. (2003) used
elderly frail subjects, our training study used sedentary subjects who were not
functionally impaired. It is difficult to know whether the smaller 21% increase in
isometric strength would still equate to functional improvements in functionally
impaired subjects. Increased strength is known to improve performance in daily
tasks such as ascending stairs (Ploutz-Snyder et al., 2002) and will positively affect
an individual’s level of independence (Janssen et al., 2002).
A vital task for
determination of independent living is the ability to rise from a chair (Hughes et al.,
1996). One of the most commonly used tests to evaluate lower limb strength is a
direct replication of this task and the primary limiting factor is quadriceps strength
(Hughes, et al., 1996). There is a suggested functional threshold for quadriceps
strength which would mean that the smallest of improvements in strength could
move an individual from below to above the threshold for certain activities. There
have been several studies that attempt to determine functional thresholds for
quadriceps strength for activities of daily living. Two have looked at gait speed, stair
ascent and descent and rising from a chair (Ploutz-Snyder, et al., 2002; Rantanen,
1998). Rantanen et al. (1998) used a group of disabled women older than 65 years
and determined that anything above 2.3Nm.kg-1 did not further increase walking
speed. Another study showed that elderly individuals that produce peak quadriceps
force less than 3.0 Nm.kg-1 substantially increased their risk of impaired gait speed,
rise from a chair performance and ascending and descending a stair case
performance (Ploutz-Snyder, et al., 2002). This is very close to the 2.8 Nm.kg-1
required to perform ADL’s as identified by Hasegawa et al. (2008). Although
previously untrained, the subject pool from the current study had a mean baseline
peak torque of 14 Nm.kg-1, far greater than this proposed threshold. If the functional
threshold of 2-3 Nm.kg-1 exists, it would be pointless to test these subjects on
functional tasks. It must be said however that the data from the current study cannot
be directly compared with Ploutzsynder et al. (2002) due to differences in isometric
strength testing protocols as the force data they used was measured at 60o of knee
extension which had the strongest correlation with the tests they were performing.
Due to the properties of the length tension curve, it is known that there would be a
difference in peak isometric torque at different testing angles. This could partly
explain some of the large differences in the strength to mass ratio. It could also just
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be that although sedentary, the subject pool used in the current study is much
younger and are much stronger. All subjects were very independent and had no
reported problems with performing activities of daily living.
Hypertension (Pescatellio et al., 2004), a high resting heart rate (Perret-Guillaume et
al., 2009), and low heart rate variability (Dekker et al., 1997) have been
demonstrated as independent predictors of cardiovascular disease. A meta-analysis
of 61 studies using individual data of 1 million people has determined that any
reductions in blood pressure will have positive effects on health (Lewington et al.,
2002). Lewington (2002) found that there is a continuous relationship down to at
least 115/75 mm.Hg-1 and that a reduction of as little as 2 mm.Hg-1 of decrease the
risk of stroke mortality or other cardiovascular issues by 7% in the middle aged.
Similarly, there appears to be a continuous relationship between resting heart rate
and mortality (Fox et al., 2007). This shows that although the 2 mm.Hg-1 reductions
achieved in this study were not statistically significant, they may be clinically
significant and still have a positive impact on an individual’s health and mortality. It
must be noted however that the Lewington et al. (2002) and Fox et al. (2007) studies
used much greater subject numbers than the current study. A limitation to this study
is the low subject numbers and a greater subject cohort would be necessary to
determine whether the small improvements seen in this study are significant or just
within the measurement variability. Although the greater reduction in resting heart
rate for the eccentric group may be artificially increased due to mismatched baseline
levels it has shown that low load eccentric cycle training can reduce resting heart
rate. In this study heart rate decreased significantly in the eccentric group, where it
did not in the concentric control did. This meant that the resting heart rate in the
eccentric group was actually lower than the concentric control by final testing. All
resting cardiovascular parameters collected in this training study have moved in a
positive direction that indicates health benefits. Despite working at much lower
cardiovascular workloads the apparent changes appear to be equivalent or greater
than that seen in the concentric control. This indicates that the same health benefits
associated with decreased resting heart rate and blood pressure are achieved from
eccentric cycling, even though the stress on the cardiovascular system is significantly
less.
120
This study has used a sedentary male model to represent the early stages of exercise
intolerance however cohorts with more severe exercise intolerance such as chronic
heart failure patients may benefit from the proposed low load eccentric ergometry.
Chronic heart failure impairs ventricular function and restricts cardiac output
resulting in symptomatic reporting of fatigue and dyspnoea at low work intensities
(Hanson, 1994).
Reduced work capacity is multifactorial but includes muscle
atrophy (Myers & Froelicher, 1991).
Additionally, peak aerobic power is an
independent risk factor for cardiovascular mortality in patients with chronic heart
disease (van den Broek et al., 1992). It has also been shown in men and women with
chronic heart disease that a 1 mL.kg.min-1 is associated with a 15% reduction in all
cause or cardiovascular mortality (Keteyian et al., 2008). It has been demonstrated
that peripheral adaptations such as improvements in muscle structure and peripheral
oxygen transport lead to an increased oxygen consumption and improve exercise
tolerance (Esposito et al., 2011). Although low load eccentric cycling in this study
did not achieve significant improvements in oxygen consumption or maximal work
capacity, it is possible that improvements in muscle structure and function in cohorts
with severe exercise intolerance may be achieved due to peripheral muscle
adaptations (Hollonszy and Coyle, 1984). This would have a positive effect on
mortality in that population. This is just one example of a cohort that could benefit.
Individuals with COPD are another cohort who suffer exercise intolerance and have
also shown improvements in maximal work capacity due to peripheral muscle
adaptations (Arizono et al., 2011).
General difficulty to cardiac rehabilitation interventions (not exercise specific) is
known to be related with long term adherence. Of particular relevance to this project
increased pain levels during exercise are a known barrier to adherence in a
physiotherapy setting (Jack et al., 2010). Exertion during exercise is often mistaken
as pain and so the lower perceived exertion associated with low load eccentric
cycling could potentially help to increase adherence during exercise programs. This
was not measured and can not be concluded from the results of this study, however it
is a possible side benefit of this type of exercise. Another factor that needs to be
considered is whether the pain associated muscle soreness after the initial session of
eccentric training, would in fact increase drop out due to increased pain. Individuals
participating in this type of exercise would need to be informed that muscle was a
121
likely outcome initially, however due to the repeated bout effect would decrease over
the subsequent sessions.
If eccentric cycling is to be utilised as an exercise modality in functionally impaired
cohorts, careful monitoring is necessary to ensure that any muscle soreness or
decreases in muscle strength as a result of the programming do not temporarily place
the individual in a vulnerable position due to a temporary decrease in muscle
strength. If the programming is not monitored carefully, there is the potential that it
will temporarily exacerbate the problems it is attempting to improve (Cleak & Eston,
1992). For example, high force eccentric training could potentially increase the risk
of falling in the short term due to decrements in strength despite the desired outcome
being an increase in strength. Large amounts of muscle soreness may also have a
negative effect on overall adherence to programs. The data from the familiarisation
sessions in both study 1 and study 2 have shown that muscle soreness is minimal at 5
minutes post session, peaks at 24 hours then systematically decreases at 48 and 72
hours.
Due to the difficulties involved with familiarisation and the relative difficulty of
obtaining eccentric cycle ergometers the future of this type of training could be
downhill treadmill walking. Future work should compare eccentric cycle ergometry
with downhill treadmill walking and determine if similar improvements in strength
and cardiovascular parameters can be achieved. Downhill walking would be more
functionally relevant in a clinical setting than cycle ergometry. If downhill walking
is to be utilised the problems associated with familiarisation will be negated as
walking down hill and down stairs is a common task. As negative work can be
defined as the product of the force absorbed and the distance over which it was
absorbed, it will remain constant as the mass of the individual and gravity will not
change. If the speed and decline of the treadmill remain constant then a consistent
amount of eccentric work should be performed. The safety of an eccentric cycle
ergometer may be greater for individuals with high risk and it could be used as a
preliminary training tool to ensure that an individual had enough eccentric strength
to be at a low risk of falling on a treadmill.
122
4.1 Limitations
Scientific study design for interventions aspire to use a double blind randomised
control model. This level of control best attenuates bias on behalf of the participants
and scientific team.
numerous reasons.
However, achieving such goals can be often difficult for
In terms of the scientific team the current project used a
randomisation model and matched subjects based off muscular strength.
Randomisation occurred prior to any training stimulus to avoid bias on the part of
baseline testing. It was not possible to utilise an independent tester due to staff and
funding restrictions however it is believed that any effects caused by the tester’s
knowledge of the subject groups was minimal. In terms of standard operating
procedures a number of criterion methods were employed. These included; Firstly,
the tester used standardised procedures and dialogue to ensure consistency between
subjects. Secondly, the primary results of training workloads, training heart rates
and isometric strength were all determined electronically via pre-written software
scripts.
This would ensure that the tester could not bias any testing procedures to
improve the results seen by the experimental group and subjects would not be
influenced by expectations associated with the experimental or control group.
In terms of subjects, one possible confounding factor is that the distinct differences
between eccentric cycling and concentric cycling were impossible to blind due to the
nature of the activity. However, in the participant information pack there was no
implied bias towards a superior adaptation or preferential mode of exercise for either
group. Therefore all subjects approached training with equal intent to improve their
health.
An additional, and possibly the largest limitation of the current study is the absence
of a test only control group. If a test only control group had been used it would have
been possible to exclude, or quantify any effects of test familiarisation.
The
rationale for using a concentric control group as opposed to a test only control group
was based off the two studies by LaStayo et al (1999; 2000). These two studies
utilised a concentric control group at similar workloads to the current study.
However these two studies did not encounter this limitation as their concentric
control did not increase strength. The reason for the improvement in strength of the
123
concentric group in the current study is unknown as the total volume of training in
the current study is less and the intensity is similar.
An additional limitation that effects this project as a whole is the ability to
extrapolate findings from one subject cohort to another. Although a sedentary male
population was used in study, the long term goal is to use low load eccentric cycling
as a training tool for developing strength in individuals suffering exercise
intolerance. The results of this study appear promising however there are limitations
in the ability to extrapolate from a sedentary cohort into an exercise intolerant or
pathology cohort. Similarly it is a limitation that the findings of study one, using a
healthy young population, were used to form the basis of the second study with a
sedentary older population.
4.2 Conclusion
This project has clearly demonstrated that an acute 30 minute bout of low load
eccentric cycling can be achieved with significantly lower cardiovascular and
metabolic stress and no difference in muscle activation or force production. When
utilised as a training modality over an 8 week program significant improvements in
strength are achieved as well as beneficial reductions in resting cardiovascular
parameters. This is very promising for the clinical setting as similar benefits can be
achieved with significantly lower stress on the cardiovascular system. Eccentric
cycling at loads submaximal to concentric peak could be particularly beneficial for
individuals with exercise intolerance as it allows an increase in strength for low
cardiovascular stress.
124
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138
Appendix A
University of Wollongong
INFORMED CONSENT: EXERCISE PHYSIOLOGY LABORATORY
Eccentric Cycling: Physiological Response to 30 minutes of Eccentric Cycling
The researchers conducting this project adhere to the Declaration of Helsinki, and follow
the principles governing both the ethical conduct of research and the protection (at all times)
of the interests, comfort and safety of experimental subjects. This form, and the
accompanying Subject Information Package, are given to you for your own protection, and
contain an outline of the experimental procedures and the possible hazards.
Your signature below indicates five things:
(1) You have received and read the Subject Information Package.
(2) You have been given the opportunity to discuss the content of this document
with one of the researchers prior to commencing the experiment.
(3) You clearly understand these experimental procedures and possible hazards.
(4) You voluntarily agree to participate in the project.
(5) Your participation may be terminated at any point without jeopardising your
present or future involvement with the University, or, in the case of a student,
your assessment for any subjects, or courses undertaken through the University.
Questions concerning the procedures, or rationale, used in this investigation are welcome at
any time. Please ask for clarification of any point that you feel is not explained to your
satisfaction. Your initial contact person is: Mr. Marc Brown (School of Health Sciences,
University of Wollongong: phone 02-4221-3495), or ultimately to Prof. Julie Steele (Head
of School of Health Sciences: phone 02-4221-3463). For further information about the
conduct of human experiments, please contact the Secretary of the Human Research Ethics
Committee, University of Wollongong (phone: 02-4221-4457).
I agree to participate in the experiment outlined in the Subject Information Package that
will be conducted within the Exercise Physiology Research Laboratory (building 41) at the
University of Wollongong.
Last name: __________________ Given name: ______________ Date of Birth: __/__/__
Address: _______________________________________________________
_______________________________________________________________
Do you give consent for photographs of yourself (dressed as described in the Subject
Information Package) to be taken during experimentation for educational/research purposes?
_______
Name and phone number of contact person in case of an emergency:
Name: _______________________________________ Phone: __________________
Family doctor: _________________________________ Phone: __________________
Signature: _____________________________________ Date: ____/____/______
Witness: Name ____________________________ Signature: ____________________
139
University of Wollongong
SUBJECT SCREENING QUESTIONNAIRE:
Exercise Physiology Research Laboratory
School of Health Sciences, University of Wollongong
Please answer the following questions as frankly and accurately as possible.
This questionnaire is designed to protect the health of both the subject and experimenter.
ALL INFORMATION OBTAINED IN THIS STUDY WILL BE KEPT CONFIDENTIAL.
NAME: _______________________________________________________
RESEARCH ID CODE: (leave blank) ________________ DATE:___________________
ADDRESS: ________________________________________________________________
______________________________________________________ Post Code ___________
TELEPHONE: Home: _______________________
Work: _____________________
DATE OF BIRTH: __________________ (dd/mm/yy) AGE: _________ years
GENDER: ( ) male
( ) female
SECTION A: OCCUPATIONAL HISTORY:
(1) Your current occupation or job:
________________________________________________
(2) Specify total period at this occupation: ______ years.
(3) As part of your present or past occupation, have you ever worked in or been exposed for
long
periods to:
( ) dusty jobs ( ) smoky jobs ( ) gas fumes ( ) chemical fumes
SECTION B: MEDICAL HISTORY:
(1) Your family or personal doctor's details:
Name: __________________________________ Telephone Number:
____________________
Address:
_____________________________________________________________________
(2) Do you have, or have you had any of these illnesses?
(a) Heart problems:
( ) yes ( ) no
If yes, please indicate the doctor’s diagnosis:
__________________________________
First incident at age: ______ years. Last incident on: ______________ (dd/mm/yy).
(b) Respiratory (lung) problem: ( ) yes ( ) no
If yes, please indicate the doctor's diagnosis:
__________________________________
First incident at age: ______ years. Last incident on: ______________ (dd/mm/yy).
140
University of Wollongong
(3) Do you have, or have you had, any of these other illnesses or health problems? For
Example: high blood pressure, diabetes, muscle, bone, joint, neural disorders or major
operations.
If no, skip to next question. If yes, please complete the details below for each item.
(a) If yes, please indicate the doctor's diagnosis: _____________________________
First incident at age: ______ years. Last incident on: ______________ (dd/mm/yy).
(b) If yes, please indicate the doctor's diagnosis: _____________________________
First incident at age: ______ years. Last incident on: ______________ (dd/mm/yy).
(c) If yes, please indicate the doctor's diagnosis: _____________________________
First incident at age: ______ years. Last incident on: ______________ (dd/mm/yy).
(4) Do you have any medical condition(s) you feel the researchers should know about?
( ) no ( ) yes: please give details: ______________________________________
(5) Are you currently taking any medication prescribed by a doctor?
( ) no ( ) yes: please give details: _______________________________________
(6) Has a doctor ever said you have a heart condition and recommended only
medically- supervised physical activity?
( ) no ( ) yes
(7) Do you have chest pain which was brought on by physical activity?
( ) no ( ) yes
(8) Have you developed non-respiratory chest pain within the past month?
( ) no ( ) yes
(9) Do you have a tendency to lose consciousness or fall over as a result of dizziness?
( ) no ( ) yes
(10) Has a doctor ever recommended medication for blood pressure or a heart
condition?
( ) no ( ) yes
(11) Do you have a bone or joint problem that could be aggravated by physical
activity?
( ) no ( ) yes
(12) Are you aware, through your own experience, or through a doctor's advice, of any
other physical reason against your exercising without medical supervision?
( ) no ( ) yes
If yes, please explain briefly: ____________________________________________
141
Appendix B
University of Wollongong
INFORMED CONSENT: EXERCISE PHYSIOLOGY LABORATORY
Eccentric Cycling: Adaptations to chronic eccentric cycle training.
The researchers conducting this project adhere to the Declaration of Helsinki, and follow
the principles governing both the ethical conduct of research and the protection (at all times)
of the interests, comfort and safety of experimental subjects. This form, and the
accompanying Subject Information Package, are given to you for your own protection, and
contain an outline of the experimental procedures and the possible hazards.
Your signature below indicates five things:
(1) You have received and read the Subject Information Package.
(2) You have been given the opportunity to discuss the content of this document
with one of the researchers prior to commencing the experiment.
(3) You clearly understand these experimental procedures and possible hazards.
(4) You voluntarily agree to participate in the project.
(5) Your participation may be terminated at any point without jeopardising your
present or future involvement with the University, or, in the case of a student,
your assessment for any subjects, or courses undertaken through the University.
Questions concerning the procedures, or rationale, used in this investigation are welcome at
any time. Please ask for clarification of any point that you feel is not explained to your
satisfaction. Your initial contact person is: Mr. Marc Brown (School of Health Sciences,
University of Wollongong: phone 02-4221-3495), or ultimately to Prof. Julie Steele (Head
of School of Health Sciences: phone 02-4221-3463). For further information about the
conduct of human experiments, please contact the Secretary of the Human Research Ethics
Committee, University of Wollongong (phone: 02-4221-4457).
I agree to participate in the experiment outlined in the Subject Information Package that
will be conducted within the Exercise Physiology Research Laboratory (building 41) at the
University of Wollongong.
Last name: __________________ Given name: ______________ Date of Birth: __/__/__
Address: _______________________________________________________
_______________________________________________________________
Do you give consent for photographs of yourself (dressed as described in the Subject
Information Package) to be taken during experimentation for educational/research purposes?
_______
Name and phone number of contact person in case of an emergency:
Name: _______________________________________ Phone: __________________
Family doctor: _________________________________ Phone: __________________
Signature: _____________________________________ Date: ____/____/______
Witness: Name ____________________________ Signature: ____________________
142
University of Wollongong
SUBJECT SCREENING QUESTIONNAIRE:
Exercise Physiology Research Laboratory
School of Health Sciences, University of Wollongong
Please answer the following questions as frankly and accurately as possible.
This questionnaire is designed to protect the health of both the subject and experimenter.
ALL INFORMATION OBTAINED IN THIS STUDY WILL BE KEPT CONFIDENTIAL.
NAME: _______________________________________________________
RESEARCH ID CODE: (leave blank) ________________ DATE:___________________
ADDRESS: ________________________________________________________________
______________________________________________________ Post Code ___________
TELEPHONE: Home: _______________________
Work: _____________________
DATE OF BIRTH: __________________ (dd/mm/yy) AGE: _________ years
GENDER: ( ) male
( ) female
SECTION A: OCCUPATIONAL HISTORY:
(1) Your current occupation or job:
________________________________________________
(2) Specify total period at this occupation: ______ years.
(3) As part of your present or past occupation, have you ever worked in or been exposed for
long
periods to:
( ) dusty jobs ( ) smoky jobs ( ) gas fumes ( ) chemical fumes
SECTION B: MEDICAL HISTORY:
(1) Your family or personal doctor's details:
Name: __________________________________ Telephone Number:
____________________
Address:
_____________________________________________________________________
(2) Do you have, or have you had any of these illnesses?
(a) Heart problems:
( ) yes ( ) no
If yes, please indicate the doctor’s diagnosis:
__________________________________
First incident at age: ______ years. Last incident on: ______________ (dd/mm/yy).
(b) Respiratory (lung) problem: ( ) yes ( ) no
If yes, please indicate the doctor's diagnosis:
__________________________________
First incident at age: ______ years. Last incident on: ______________ (dd/mm/yy).
143
University of Wollongong
(3) Do you have, or have you had, any of these other illnesses or health problems? For
Example: high blood pressure, diabetes, muscle, bone, joint, neural disorders or major
operations.
If no, skip to next question. If yes, please complete the details below for each item.
(a) If yes, please indicate the doctor's diagnosis: _____________________________
First incident at age: ______ years. Last incident on: ______________ (dd/mm/yy).
(b) If yes, please indicate the doctor's diagnosis: _____________________________
First incident at age: ______ years. Last incident on: ______________ (dd/mm/yy).
(c) If yes, please indicate the doctor's diagnosis: _____________________________
First incident at age: ______ years. Last incident on: ______________ (dd/mm/yy).
(4) Do you have any medical condition(s) you feel the researchers should know about?
( ) no ( ) yes: please give details: ______________________________________
(5) Are you currently taking any medication prescribed by a doctor?
( ) no ( ) yes: please give details: _______________________________________
(6) Has a doctor ever said you have a heart condition and recommended only
medically- supervised physical activity?
( ) no ( ) yes
(7) Do you have chest pain which was brought on by physical activity?
( ) no ( ) yes
(8) Have you developed non-respiratory chest pain within the past month?
( ) no ( ) yes
(9) Do you have a tendency to lose consciousness or fall over as a result of dizziness?
( ) no ( ) yes
(10) Has a doctor ever recommended medication for blood pressure or a heart
condition?
( ) no ( ) yes
(11) Do you have a bone or joint problem that could be aggravated by physical
activity?
( ) no ( ) yes
(12) Are you aware, through your own experience, or through a doctor's advice, of any
other physical reason against your exercising without medical supervision?
( ) no ( ) yes
If yes, please explain briefly: ____________________________________________
144
Appendix C
Physical Activity Assessment
Descriptions of MODERATE and VIGOROUS physical activity and examples of
each are listed in the boxes below.
MODERATE: Like Walking Fast
Walking fast
Walking Downstairs
Bicycling slow
Bowling
Carpentry
Dancing
Gardening (planting, raking, weeding) Frisbee
Housework (mopping,sweeping)
Gymnastics
Lifting, turning, carrying: < 23kg
Mowing Lawn
Playing with children
Sailing
Tai Chi
Volley Ball
Aqua Aerobics
Washing/working on car
Aerobics, (Low impact)
Calesthenics, light
Fishing, Standing
Golf
Horseback Riding
Ping Pong
Skateboarding
Yoga
Circle the MODERATE activities you do for at least 10 minutes at a time without
stopping during an average week.
During an average week, on how many days did you do moderate physical activity for
at least 10 minutes at a time without stopping?
Days
On those days, how much time did you spend on average doing MODERATE
physical activities?
Minutes/ Day
VIGOROUS: Like Jogging or Running
Jogging, Running
Carrying loads > 23kg
Bicycling fast
Roller skating/blading
Rowing machine
Walking Upstairs
Basketball
Judo/karate/kickboxing
Stair climbing/stair master
Swimming laps
Aerobics (high impact)
Calesthenics, vigorous
Jumping Rope
Soccer
Tennis/Squash
Circle the VIGOROUS activities you do for at least 10 minutes at a time without
stopping during an average week.
During an average week, on how many days did you do VIGOROUS physical
activity for at least 10 minutes at a time without stopping?
Days
On those days, how much time did you spend on average doing VIGOROUS
physical activities?
Minutes/ Day
Over the last year have your activity levels:
levels:
increased
decreased
remained the same
Over the last 5 years have your activity
increased
decreased
remained the same
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