CARDIFF METROPOLITAN UNIVERSITY
Prifysgol Fetropolitan Caerdydd
CARDIFF SCHOOL OF SPORT
DEGREE OF BACHELOR OF SCIENCE (HONOURS)
SPORT CONDITIONING, REHABILITATION AND
MASSAGE
2015-6
ISOMETRIC MID-THIGH PULL vs. PLYOMETRIC POST
ACTIVATION POTENTIATION AND THEIR EFFECTS ON
MAXIMUM VELOCITY IN ATHLETIC MALES
SCRAM
LOUIE SIMS
ISOMETRIC MID-THIGH PULL vs. PLYOMETRIC POST
ACTIVATION POTENTIATION AND THEIR EFFECTS ON
MAXIMUM VELOCITY IN ATHLETIC MALES
Cardiff Metropolitan University
PrifysgolFetropolitanCaerdydd
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02.04.2016
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TABLE OF CONTENTS
Acknowledgements ............................................................................................................i
Abstract...............................................................................................................................ii
CHAPTER 1: INTRODUCTION ...........................................................................................1
1.0 INTRODUCTION ............................................................................................................2
1.1 Importance of linear sprinting and limb stiffness.......................................................3
CHAPTER TWO: REVIEW OF LITERATURE.....................................................................4
2.0 LITERATURE REVIEW..................................................................................................5
2.1 Potentiating Stimulus, contraction type and recovery time ..................................5
2.2 Underpinning Kinetics and Kinematics of Sprinting ............................................9
2.3 Aims of the Study ..............................................................................................10
CHAPTER THREE: METHODOLOGY ..............................................................................11
3.0 METHODOLOGY..........................................................................................................12
3.1 Experimental Approach to the Problem.............................................................12
3.2 Participants........................................................................................................12
3.3 Instruments .......................................................................................................13
3.4 Testing Procedures ...........................................................................................14
3.4.1 Control Trial..........................................................................................14
3.4.2 Plyometric PAP ...................................................................................15
3.4.3 Isometric PAP ......................................................................................15
3.5 Video Analysis....................................................................................................16
3.6 Data Analysis ....................................................................................................17
CHAPTER FOUR: RESULTS ...........................................................................................18
4.0 RESULTS ....................................................................................................................19
4.1 30-40 meter times .............................................................................................19
4.2 Average step length.......................................................................................... 20
4.3 Average step frequency.....................................................................................21
4.4 Percentage change in 30-40 meter times..........................................................22
4.5 Plyometric PAP step length and step frequency relationship.............................23
4.6 Isometric PAP step length and step frequency relationship...............................24
4.7 Relative peak force and percentage change in 30-40m time ............................25
CHAPTER FIVE: DISCUSSION.........................................................................................26
5.0 DISCUSSION................................................................................................................27
5.1 Volume effects on PAP ......................................................................................27
5.2 Contraction type effects on PAP........................................................................29
5.3 Rest period effects on PAP................................................................................30
5.4 Subject strength levels and training age effect on PAP.....................................31
5.5 Changes in average step length and step frequency.........................................33
5.6 Limitations and future research..........................................................................34
CHAPTER SIX: PRACTICAL APPLICATIONS AND CONCLUSIONS.............................35
6.0 PRACTICAL APPLICATIONS AND CONCLUSIONS...................................................36
REFERENCES...................................................................................................................37
APPENDICIES
Appendix A ............................................................................................................A-1
Appendix B ............................................................................................................B-1
Appendix C ............................................................................................................C-1
List of Tables
Table 1: Standardised Warm-up protocol...........................................................................14
List of Figures
Figure 1: The Relationship between Potentiation and Fatigue............................................8
Figure 2: Schematic representation of the Study Design...................................................12
Figure 3: Individual 30-40m times for Control vs. Plyometric PAP....................................19
Figure 4: Individual 30-40m times for Control vs. Isometric PAP.......................................19
Figure 5: Individual average step length for Control vs. Plyometric PAP...........................20
Figure 6: Individual average step length for Control vs. Isometric PAP.............................20
Figure 7: Individual average step frequency for Control vs. Plyometric PAP.....................21
Figure 8: Individual average step frequency for Control vs. Isometric PAP.......................21
Figure 9: Difference between %change in 30-40m times .................................................22
Figure 10: Correlation between Plyometric step length and step frequency %change......23
Figure 11: Correlation between Isometric step length and step frequency %change........24
Figure 12: Correlation between Relative Peak Force and Plyometric %change...............25
Figure 13: Correlation between Peak Force and Isometric %change................................25
ACKNOWLEDGEMENTS
Foremost, I would like to thank Jason Pedley on his outstanding support and guidance
throughout the process, and also Rob Meyers and the other members of the S&C team for
their time and acceptance of random discussions.
Thanks to all the participants that took part in the study and maintained their reliability
throughout the process.
Thanks to my parents and girlfriend for keeping me focussed and motivated through
university.
i
ABSTRACT
Postactivation potentiation (PAP), an acute enhancement of muscular performance
observed after a preconditioning stimulus, has been reported to increase sprint
acceleration performance after a variety of contraction types. Very few studies have
analysed different contraction type effects on subsequent sprint performance, with no
current studies solely investigating the maximal velocity phase of sprinting or kinematic
data, therefore the present study examined the effects of both isometric mid-thigh pulls
(IMTP) and plyometric pogo hops (PPH) on subsequent maximum velocity phase sprinting
performance. In a randomized crossover study design, athletic men (n = 13) performed a
standardised warm up with no further PAP stimulus (C) or the standardised warm up
followed by 3 sets of 5s maximal isometric contraction (IMTP) or 3 sets of 20 plyometric
hops (PPH). 8 minutes of passive rest was utilised and then subjects performed three 45m
sprints each separated by 4 minutes rest (with the 30-40m split being analysed). 2D video
analysis was used to calculate changes in step length and frequency between trials and
force data was also collected during the IMTP. Repeated measures ANOVA indicated no
significant differences between PPH and IMTP 30-40m times (p= 1.00) and IMTP vs. C 3040m times (p= .064). A significant decrease in performance was observed between PPH
and C 30-40m times (p= .05). No significant differences were observed in C vs. PPH
average step length (p= .168), C vs. IMTP (p= 1.00) and PPH vs. IMTP (p= .281). No
significant differences were observed between C vs. PPH (p= 1.00) and C vs. IMTP
average step frequency (p= .216). Differences in PPH vs. IMTP average step frequency
approached significance (p=0.53). There were also no significant differences in
performance responses between the strongest and weakest subjects but large variations
in individual responses were found between the subjects. The findings suggest that the
present protocol in the present subject population will lead to decreases in maximal
velocity sprint performance. However large individual responses were present and thus
PAP should be considered on an individual basis. Factors including contraction type,
volume, intensity and rest period should be carefully considered in PAP practical
application, with future research aiming to utilise a similar protocol in elite populations.
ii
CHAPTER 1
INTRODUCTION
1
1.0 Introduction
Optimal training protocols to maximize performance are greatly sought after by coaches
and athletes (Lim and Kong, 2013). The ability to maximise muscular power (Wilson et al.,
2013) and limb stiffness (Chelly and Denis, 2001) is critical for successful outcomes in a
variety of sports, especially in relation to sprinting performance (Chelly and Denis, 2001).
Therefore a protocol that enables maximal physical performance is desirable. The use of
strength and power potentiating complexes is one method to utilise explosive strength in
athletes (Stone et al., 2008). This entails performing near maximal contractions followed
by a biomechanically similar explosive movement, this training technique utilises
postactivation potentiation (PAP). PAP is defined as an increase in muscle twitch and low
frequency tetanic force after a previous conditioning contractile activity (Sale, 2002). PAP
is a theoretical concept that suggests the contractile history of a muscle influences the
performance of subsequent contractions (Lorenz, 2011). Two principal mechanisms have
been proposed for PAP, the first is the phosphorylation of myosin regulatory light chains, in
which actin-myosin interaction is sensitised to Ca2 released from the sarcoplasmic
reticulum during subsequent contractions (Grange, Vandenboom and Houston, 1993; Sale
2002; Judge, 2009). Also, the myosin light chain kinase, responsible for increasing ATP
availability at the actin-myosin complex increases the rate of actin-myosin cross bridging
(Xenofondos et al., 2010), thus increasing the power output of the cross bridges and in
turn improving performance of explosive movements (Hodgson, Docherty and Robbins,
2005).
The Second mechanism is the increase in the recruitment of high order motor units
(Tubman et al., 1996; Chiu et al., 2003). However increased neural activity has also been
attributed to better synchronization of motor units and decreases in presynaptic inhibition
(Aagaard, 2002; Xenofondos et al., 2010). There is also evidence to suggest that changes
in pennation angle after a conditioning stimulus may contribute to PAP (Tillin and Bishop,
2009; Xenofondos et al., 2010). Thence the PAP effect may be a result of neural and
muscular mechanisms of which are not fully understood at this time.
Although the physiological mechanisms underpinning PAP are not fully understood,
muscle performance has been shown to increase after conditioning tetanus (Abbate et al.,
2000; Trimble and Harp, 1998), subfusion stimuli (Macintosh and Willis, 2000), or maximal
voluntary contraction (MVC) (Vandervoort, Quinlin and McComas, 1983; Gullich and
Schmidtbleicher, 1996; Smilios et al., 2005).
2
Concerning MVC, maximal isometric contractions (Gullich and Schmidtcleicher, 1996;
Hamada et al., 2000), high intensity resistance exercise (Jensen and Ebben, 2003;
McBride, Nimphus and Erickson, 2005), ballistic movements with resistance (Smilios et al.,
2005) and plyometric exercise (Masamoto, 2003) have all been shown to have a positive
effect on performance when used as potentiating exercises in various athletic movements.
Furthermore, voluntary muscle actions have been shown to elicit a PAP response for
ballistic movements in the lower limbs (Young, McLean and Ardagna, 1995; Young,
Jenner and Griffiths, 1998; Grant, Young and Aitken, 2002; Gourgoulis et al., 2003),
however this was not the case for peak isometric force (Gossen and Sale, 2000) or the
unloaded shortening velocity (Shorten, 1987). Moreover, it has also been reported that
plyometrics can cause PAP for maximal isometric voluntary contraction (Masamoto et al.,
2003).
1.1 Importance of linear sprinting and limb stiffness
Linear sprint performance has been shown to be an important determinant of matchwinning actions in a wide variety of sports (Schneiker et al., 2006; Alemdaroğlu, 2012), as
opposed to just track and field event outcome (Winchester et al., 2008; Judge, 2009).
Faude, Koch and Meyer (2012) found that straight sprinting is the most frequent action in
goal situations in professional football with 45% of goals in the German League being
preceded by a linear sprint by the scoring or assisting player (Faude et al, 2012). To date a
number of studies have examined the acute effects of heavy back squats (Yetter and Moir,
1999; Mcbride, NimphIus and Errickson, 2005; Chatzopoulous et al., 2007), Plyometrics
(Till and Cooke, 2009; Byrne, Kenny and O’ Rourke, 2014), and Sled Pulls (Whelan,
O'Regan and Harrison, 2014; Winwood et al., 2015) on sprint performance. The existing
literature has found significant improvements to sprint performance over from distances of
10-40m, however the PAP stimuli, rest periods and subjects utilised have been varied
(Byrne, Kenny and O’ Rourke, 2014). Leg stiffness has been significantly correlated with
maximal velocity, with individuals with greater levels of lower limb joint stiffness being able
to achieve a higher maximal velocity (Arampatzis, Brüggemann and Metzler, 1999;
Kuitunen, Komi and Kryöläinen, 2002). Studies investigating the effects of plyometric
exercise on stiffness in relation to PAP have reported significant increases in limb stiffness
post-activation (Barnes et al., 2015), however existing literature looking at isometric
contractions and their effects on limb stiffness have been inconclusive (Kay and Blazevich,
2009; Gago et al., 2014).
3
CHAPTER 2
REVIEW OF LITERATURE
4
2.0 Literature Review
2.1 Potentiating Stimulus, contraction type and recovery time
Previous research has focussed on the effects of PAP on performance using dynamic
movements (Young, Jenner and Griffiths, 1998; Baker, 2003; Gourgoulis et al., 2003; Scott
and Docherty, 2004; McBride, Nimphus and Erickson, 2005) and isometric maximum
voluntary contractions (French, Kraemer and Cooke, 2003; Gossen and Sale, 2000;
Gullich and Schmidtbleicher, 1996). A majority of research on dynamic lower body
exercise has used the squat exercise and measured PAP using the vertical jump test
(Young, Jenner and Griffiths, 1998; Gourgoulis et al., 2003; Jensen and Ebben, 2003;
Jones and Lees, 2003; Scott and Docherty, 2004), horizontal jumps (Radcliffe and
Radcliffe, 1996) and drop jumps (Gullich and Schmidtbleicher, 1996; French, Kraemer and
Cooke, 2003). Although both dynamic and isometric maximum contractions have been
shown to elicit a PAP response, a wide variety of exercises, rest periods and protocols
have been utilised (Till and Cooke, 2009). Therefore, there still exists a wide variety of
methods used to utilise PAP, highlighting the uncertainty of which is the most effective
protocol to elicit the PAP response (McBride, Nimphus and Erickson, 2005). Reviews have
shown that it is possible to elicit a PAP response in highly trained, recreationally trained
and untrained populations (Ebben, 2002; Docherty, Robbins and Hodgson, 2004;
Hodgson, Docherty and Robbins, 2005), however most studies utilised jump performance
as a marker of the PAP effect. The effect of PAP on practical, athletic performance
therefore remains unclear (Winwood et al., 2015). The current body of evidence suggests
that PAP could have a significant effect on performance, with PAP shown to increase the
rate of force development (RFD) and thus could be utilised to improve the performance of
athletic movements such as the acceleration and the maximum velocity phases of
sprinting (Vandenboom, Grange and Houston, 1995; Batista et al., 2007; Judge, 2009).
The current body of literature regarding PAP on sprint performance is highly focussed on
acceleration (Gullich and Schmidtbleicher, 1996; French, Kraemer and Cooke, 2003;
Chatzopoulos et al., 2007; Rahimi, 2007; Yetter and Moir, 2008; Till and Cooke, 2009;
Bevan, 2010; Comyns, Harrison and Hennessy, 2010; Linder, 2010) with no current
studies found solely investigating the maximum velocity phase of sprinting. Chatzopoulos
et al. (2007) investigated PAP on running speed and found significant increases after 10
reps of 90% 1RM performed as singles after 5 minutes rest when compared to the control.
There is also a lack of literature comparing different contraction types as a potentiating
5
stimulus for sprinting. Lim and Kong (2013) investigated single-joint isometric, multijoint
isometric and multi-joint dynamic potentiating stimuli on 30m sprint times. The study
concluded that none of the protocols had a significant effect after 4 minutes postactivation. However both of the studies mentioned utilised acceleration phase type
distances (>30m) (Wild et al., 2011). Therefore there is a lack of research within the area
of the PAP effect on the max velocity phase of sprinting.
Chatzopoulos et al. (2007) reported that after 10 single squat repetitions (at 90% of 1RM)
0-30m times and running speed were significantly improved after 5 minutes, but not 3
minutes post-activation, in 15 amateur team sports players. McBride, Nimphus and
Erickson (2005) reported that after 3 repetitions of back squats at 90% of one repetition
maximum (1RM) 40m sprint performance was significantly increased after 4 minutes postactivation, however at 10m and 30m no significant differences in sprint time were
observed, with performance increases being observed at 30-40m. Yetter and Moir (2008)
conducted a study which compared progressive sets of back squats against front squats
(30-70% 1RM) and a control, 0-40m trials were found to be significantly faster in the back
squat protocol than vs. control and front squat 4 minutes post-activation. Interestingly, as
in Mcbride, Nimphius and Erickson (2005) the most significant increase in performance
was during the 30-40m interval, given that maximum velocity is usually achieved at ~30m
(Dolenec and Čoh, 2009), this supports the hypothesis that the maximal velocity phase of
sprinting could be influenced by PAP.
To date there is no uniform agreement about the optimal recovery time between preload
stimuli and explosive activity (Kilduff et al., 2007). Previous studies have used rest
intervals ranging from 0 to 18.5 minutes (Young, Jenner and Griffiths, 1998; Baker, 2003;
Chiu et al., 2003; Gourgoulis et al., 2003). Minimal studies have solely examined the
optimal time between the preload stimulus and subsequent explosive activity (Jensen and
Ebben, 2003; Kilduff et al., 2007). Jensen and Ebben (2003) examined rest periods of 10
seconds, 1, 2, 3 and 4 minutes between the preload stimulus (5RM squat) and subsequent
explosive activity, the study concluded that there was no effect on jumping ability after any
of the rest periods; however the author highlighted that a rest period greater than 4
minutes may show an effect on performance. Jones and lees (2003) reported no
significant change in performance following 3, 10 and 20 minutes of rest following heavy
squats, however due to a small sample size (n=8) statistical tests carried minimal power.
Chiu et al. (2003) reported that average and peak power were significantly greater at 18.5
minutes post-activation compared to 5 minutes post-activation, however these were the
only time points that results were measured, meaning the optimal time could lay anywhere
6
between the two times. In light of the previous studies, Kilduff et al. (2007) set out to
determine the most effect rest period greater than 4 minutes using a 3RM back squat. The
study concluded that the optimal recovery to maximise the PAP effect lies between 8-12
minutes. Whelan et al. (2014) investigated the effect of sled sprints at 30% of bodyweight
on 10m sprint performance after 1, 2, 4, 6, 8 and 10 minutes of exercise, the study found
no significant differences in 10m times vs. control. In light of previous research, Winwood
et al. (2015) investigated the effect of 150% and 75% of bodyweight sled pulls on sprint
performance 4, 8 and 12 minutes post-activation. The study concluded that the 75% body
mass sled pull improved 15m sprint performance, providing that 8 to 12 minutes recovery
was allowed.
A majority of sprinting studies used dynamic PAP protocols (Chatzopoulos et al., 2007;
Rahimi, 2007; Yetter and Moir, 2008; Till and Cooke, 2009; Bevan, 2010; Comyns,
Harrison and Hennessy, 2010; Linder, 2010) with few utilising an isometric PAP protocol
(Till and Cooke, 2009). A majority of the studies that utilised a dynamic protocol have
utilised the squat to elicit PAP, however further studies have utilised plyometrics as a PAP
stimulus (Hilfiker et al., 2005, Till and Cooke, 2009, Byrne, Kenny and O’ Rourke, 2014;
Turner et al., 2015). Till and Cooke (2009) reported that 5 tuck jumps were not effective to
significantly improve 10-20m sprint performance in twelve male soccer players 4, 5 and 6
minutes post-activation. Turner et al. (2015) investigated the effects of 3 sets of 10
repetitions of alternate-bounding with bodyweight and a weighted vest (10% of
bodyweight) vs. a control on 20m sprint times. Significant increases were observed after
the weighted vest condition 4 and 8 minutes post-activation vs. control and 4 minutes postactivation in the bodyweight condition. Byrne, Kenny and O’ Rourke (2014) investigated
the effect of a drop jump (predetermined by using the maximum jump method) and found
significant improvements in 20m times vs. control at 1 minute post-activation. Till and
Cooke (2009) found that 3 sets of 3 seconds maximal isometric knee extension had no
effect on 20m sprint times 4, 5 and 6 minutes postactivation. Given the similar musculature
involved with the squat exercise, sled pull, plyometric and isometric PAP studies (Schache
et al., 2012), key findings of the reviewed literature can be drawn upon to inform the author
of optimal rest periods to elicit the PAP response.
It is generally accepted that different contraction types will cause differing levels of fatigue
(Xenofondos et al., 2010), given the coexistence of potentiation and fatigue different
amounts of time will be needed between the potentiating stimulus and subsequent
performance measure in order to achieve a potentiated state (Rasier and Macintosh,
2000) (figure 1).
7
Figure 1: The Relationship between Potentiation and Fatigue
Isometric contractions are reported to recruit a greater number of muscle fibres than
dynamic contractions, potentially resulting in a greater percentage of regulatory chain
phosphorylation as well as alterations in muscular architecture (Tillin and Bishop, 2009).
Lactate accumulation occurs at a faster rate during dynamic contractions resulting in faster
peripheral and neuromuscular fatigue (Karelis, Marcil and Peronnet, 2004), given that
fatigue and potentiation coexist these findings could be important (Rasier and Macintosh,
2000). Lim and Kong (2013) investigated isometric vs. dynamic potentiation protocols on
sprint performance, the findings of the study were inconclusive between the conditions and
found high variability of the effectiveness of PAP between individual subjects. The latter
finding is coherent with the current literature, with variations of -7.1% to +8.2% being
reported (Till and Cooke, 2009), with the variability being attributed to muscle fibre type
(Sale, 2002), performance level (Young, McLean and Ardagna, 1995; Gourgoulis et al.,
2003), exercise type (Lim and Kong, 2013), time interval between the conditioning stimulus
and the performance testing (Kilduff et al., 2007), and gender (Linder et al., 2010).
8
2.2 Underpinning Kinetics and Kinematics of Sprinting
General similarities between the acceleration and maximal velocity phase of sprinting
exist, such as the triple extension (proximal-to-distal hip, knee, ankle sequencing),
however, both subtle and gross differences can also be identified between accelerative
and maximum velocity sprinting from existing literature (Wild et al., 2011). A key difference
between the two phases is ground contact time, it has been reported that with an increase
in velocity comes a decrease in ground contact time (Wild et al., 2011). In a controversial
study Weyand et al. (2000) found that reducing ground contact times and producing a
greater ground reaction force (GRF) at maximum velocity allows for faster running speeds,
not faster leg movements. Therefore given that PAP has been shown to increase RFD
(Batista et al., 2007; Judge, 2009) it can be hypothesised that PAP may influence maximal
velocity.
At the maximal velocity phase of sprinting hip and knee kinematics remain fairly constant
with minimal changes in hip and knee angles during ground contact (Mann and Hagy,
1980; Wild et al., 2011). Leg stiffness has been reported to increase as running velocity
increases (Arampatzis, Brüggemann and Metzler, 1999), allowing the body to utilise the
stretch shortening cycle (SSC) more efficiently (Wild et al., 2011), however to date no
studies have investigated the effect of different contraction types on SSC in relation to
PAP. Leg stiffness has been significantly correlated with maximal velocity, with individuals
with greater levels of lower limb joint stiffness being able to achieve a higher maximal
velocity (Arampatzis, Brüggemann and Metzler, 1999; Kuitunen, Komi and Kryöläinen,
2002). The most commonly reported mechanism of stiffness control is co-contraction of
agonist and antagonist muscles (Hortobágyi and Devita, 2000), however minimal studies
have been conducted on isometric PAP effects on limb stiffness (Kay and Blazevich, 2009;
Gago et al., 2014). Kay and Blazevich (2009) found that isometric contractions reduced
Achilles tendon stiffness, however in a more recent study Gago et al. (2014) reported that
isometric contraction can be used to induce PAP without imparing tendon stiffness.
Plyometric exercises are commonly used in sprinting warm-up protocols (Goodwin, 2011),
with plyometric exercise found to significantly increase joint stiffness (Foure et al., 2009;
Foure, Nordez and Cornu, 2010; Foure, Nordez and Cornu, 2012). Barnes et al. (2015)
found that a sub maximal warm up followed by 10 strides with a weighted vest (20% of
bodyweight) followed by 10 minutes recovery resulted in a large enhancement of peak
running speed, a moderate increase in leg stiffness and a large improvement in running
economy in 11 well trained distance runners. The increases in running economy were
9
attributed to potentiation of leg stiffness and the author postulated that treadmill
performance enhancement would translate into competitive endurance performance. The
importance of limb stiffness is not limited to the track and field athlete (Pruyn, Watsford
and Murphy, 2014), with improved running economy being beneficial to any sport inclusive
of running, potentially limiting energy expenditure (Barnes et al., 2015), improving sprinting
ability (Arampatzis, Brüggemann and Metzler, 1999; Kuitunen, Komi and Kryöläinen, 2002)
and thus potentially causing improvements in performance.
2.3 Aims of the Study
Therefore, due to the lack of research concerning PAP at maximal velocity sprinting and
lack of research comparing different PAP protocols, it would be interesting to investigate
the effect that both plyometric and isometric potentiating exercises have on maximal
velocity sprinting. Ideally a stiff leg would provide a predominantly isometric muscle action,
however, inevitably a lot of fast, high force eccentric contractions occur (Chatzopoulos et
al., 2007; Rahimi, 2007; Yetter and Moir, 2008; Linder, 2010; Wild et al., 2011). This study
will utilise key findings from previous research regarding rest periods and stimulus intensity
to compare the PAP effect of both an isometric and plyometric potentiating protocol to a)
determine the PAP effects on group maximal velocity; b) compare the PAP effects of a
plyometric exercise and isometric mid-thigh pull on maximal velocity c) examine the
variation in individual responses after PAP protocols and d) analyse sprint kinematic data
to propose a mechanism for potential differences between trials.
10
CHAPTER 3
METHODOLOGY
11
3.0 Methodology
3.1 Experimental Approach to the Problem
This investigation used a cross-over randomised design involving 2 conditions (Isometric
MVC and Plyometric) and their effects on maximum velocity sprinting (30-40m) when
compared to a control trial (figure 1). Sprint time splits were measured at 0-30m and the
30m-40m mark. It was hypothesised that both the isometric and plyometric protocols
would have a PAP effect on maximum velocity, thus improving subjects sprint
performance. However, it was assumed that the plyometric stimulus would elicit a greater
PAP effect than the isometric MVC. This design allows the different PAP protocols to be
examined as well as examining PAP and its usefulness in potentially improving maximal
velocity sprinting in athletic males.
Warm up
4 minute rest
Plyometric PAP
3 x 20 pogo hops
3-minutes ISR
Isometric PAP
3 x 5s IMTP
3-minutes ISR
Control
4-minute rest
8 minutes passive
rest
Sprint Trials
3x 45 m
4-minutes ISR
Figure 2. Schematic representation of the study design. IMTP= isometric mid-thigh pull, ISR = inter-set rest.
3.2 Participants
13 Male Cardiff Metropolitan University students took part in the study (age 19.2 ± 1.2
years, height 1.78 ± 0.07 m, mass 79.9 ± 10.1 kg). Testing protocol and possible risks
were explained prior to testing; all subjects then filled out a Physical Activity Readiness
Questionnaire (PAR-Q) and signed an informed consent document in accordance with the
Cardiff Metropolitan University Ethics Committees guidelines before testing began (see
appendix A, B and C).
12
All subjects were actively engaged in sport (American football, n=1; Athletics, n=1;
Badminton, n=1; Boxing, n=1; Football, n=3; Gymnastics, n=1; Rugby, n=5) for a minimum
of 12 months, with resistance training being incorporated in training for their given sport as
poor strength levels have been identified to inhibit sprint ability (Goodwin, 2011), as well as
the PAP response (Young, McLean and Ardagna, 1995; Gourgoulis et al., 2003).
Furthermore, gender has been shown to effect the PAP response, thus a male population
was utilised (Linder et al., 2010). Participants had previous experience in relation to
plyometric exercise and were free from injury at the time of the study. Subjects were
instructed to refrain from eating 2 hours before testing and consuming alcoholic or
caffeinated drinks 24 hours prior to each testing appointment (Kilduff et al., 2007).
Participants were also instructed to have regular sleep and refrain from any additional
lower limb training 48 hours prior to testing (McBride, Nimphus and Erickson, 2005;
Chatzopoulos et al., 2007).
3.3 Instruments
Subject’s height and weight was measured prior to the first testing appointment. Height
was obtained to the nearest 0.1cm using a fixed stadiometer (Holtain, Fixed Stadiometer,
Crosswell, UK) and mass was recorded to the nearest 0.1kg using digital scales (SECA,
770, Hamburg, Germany). Timing gates (Fusion Sport, Smart Speed, Coopers Plains,
Australia), consisting of reactive data units coupled with reflector units affixed on top of
tripods, were used to obtain a 10 metre split time from 30m-40m for each trial. Reactive
data units were synchronized with a handheld computer (Sony, Vaio, Tokyo, Japan) which
included customized software to record sprint time. Each split time was recorded in to an
excel spreadsheet (Microsoft, USA). Gates were placed at a height of 1.2 m for all tests
(Oliver and Meyers, 2009), and subjects began each sprint 30 cm behind the start line in
order to trigger the first gate (Oliver and Meyers, 2009). A video camera (Apple, iPad Mini,
California, USA) was mounted on a tripod placed perpendicular to the running lane 16m
away in order to record the 30-40m part of the sprint for each condition. The captured
videos were used to calculate average step length and step frequency. All video data was
recorded at 50 frames per second (FPS) through the Coaches Eye® (TechSmith, USA)
application.
The timing gates that were utilised in the study have been found to be reliable and valid
when recording linear speed in athletic populations (Green et al., 2010).
13
3.4 Testing Procedures
Participants participated in 3 testing sessions each separated by 7 days, involving the two
potentiating protocols (isometric mid-thigh pull and plyometric) and the control protocol.
Prior to each condition subjects underwent a standardized warm-up modified from Ebben
and Petushek (2010) and Till and Cooke (2009) (see Table 1). The participants were
required to do 3x 45m sprints; the first 30m being a flying start to ensure maximal velocity
was reached upon reaching the 30m mark (Dolenec and Čoh, 2009). A 45m section of
track was measured out using a tape measure (SECA, 201, Hamburg, Germany), using
the track lines to retain a straight line. The timing gates were then positioned on 0, 30 and
40m, with a fourth “dummy” gate being placed at 45m in order to prevent participants from
decelerating before the 40m mark. All participants began sprint trials from a split stance in
standing as this has been identified as the most reliable and optimal stance in which to
accelerate from in similar sample populations (Cronin et al., 2007; Johnson et al., 2010).
Table 1: Standardised Warm-up Protocol
Warm-up Exercise
Distance
Light jog
Walking lunges
200m
10m
Squats
Inchworms
Spiderman
10m
10m
10m
High knees
Progressive runs (60, 70, and 80%)
20m
40m
The following describes each testing condition completed in a randomized order:
3.4.1 Control Trial
The standardised warm up was performed and then 4 minutes of rest was allowed,
participants then performed 3x 45m sprints with 4 minutes rest between trials (Yetter and
Moir, 2008; Sapstead and Duncan, 2013).
14
3.4.2 Plyometric PAP
Plyometric exercises focusing on vertical force production were utilised as the maximum
velocity phase of sprinting has been shown to be reliant upon on vertical rather than
horizontal ground reaction force (Weyand et al., 2000). After the warm up was performed 4
minutes rest was allowed, participants then performed 20 pogo hops (Ruben et al., 2010).
The participants were instructed to spring from the floor with both legs, with particular
instruction being directed towards being stiff, fast and powerful (Ruben et al., 2010). After
a period of recovery (~3minutes), two further sets were completed (Turner et al., 2015).
Eight minutes of passive rest then occurred consisting of walking in order to maintain body
temperature, in which no additional stretching or warm up activities were allowed
(McBride, Nimphius and Erickson, 2005). Participants then performed 3x 45m sprints with
4 minutes rest between trials (Yetter and Moir, 2008; Sapstead and Duncan, 2013; Seitz
and Haff, 2015).
3.4.3 Isometric PAP
The isometric mid-thigh clean pull was chosen because it corresponds to the portion of the
clean where the highest forces are generated (Garhammer, 1998). Participants were
instructed to pull on an immovable Olympic bar (York Barbell Co., York, Pennsylvania)
(performed in a power rack with pins) as quickly as possible, and maintain a maximal
effort for 5 seconds, a duration utilised in previous isometric PAP studies (Berning et al.,
2010; Esformes et al., 2011; Sapstead and Duncan, 2013). The subjects performed all
trials on a force plate (AMTI, Accupower, Boston, USA) recording at a sample rate of 20Hz
in order to obtain force data. After the subjects were placed in to position, knee angles
(141±10°) were measured with a Goniometer (Biometrics, F35, Newport, UK) in order to
ensure that the position was accurately reproduced during each trial (Kawamori et al.,
2006). Three sets were performed in total with ~3 minutes rest between sets (Turner et al.,
2015). Eight minutes of passive rest then occurred consisting of walking in order to
maintain body temperature, in which no additional stretching or warm up activities were
allowed (McBride, Nimphius and Erickson, 2005), before participants performed 3x 45m
sprints with 4 minutes rest between trials (Yetter and Moir, 2008; Sapstead and Duncan,
2013; Seitz and Haff, 2015).
15
3.5 Video Analysis
The subjects fastest trial (Bevan et al., 2010) was analysed in the Coaches Eye®
(TechSmith, USA) application to obtain average SL and SF over the 30-40m split.
A 2 way mixed intraclass correlation coefficient (ICC) was calculated from 31 video trials,
all independently analysed by 2 separate analysts (Weir, 2005). A high degree of reliability
was found between the video times extracted from the video data. The average measure
ICC was 1.000 with a 99% confidence interval from 1.00 to 1.00.
Steps taken within the 10m were counted initially, coloured tape (ShurTech, Color Duck
Tape, Ohio, USA) was placed on the 30m and 40m mark, a step was counted if the foot
was in contact with either of the strips of tape at touchdown or between the two pieces of
tape. The 30-40m split time was divided by the amount of steps taken to calculate average
velocity. The time between the first step to the final step (total step time) was then
calculated as follows:
St = t – ((s1 – c1) + (c2 – s2))
Where (St) represents total step time, (t) is 30-40m split time, (s1) is the time of the first
step, (c1) is the time at which the 30m line was crossed, (c2) represents the time at which
the 40m line was crossed and (s2) represents the time of the final step.
Step time was then used to calculate the average step length:
Sl = St x v
ts
Where (Sl) represents average step Length, (St) is total step time, (v) is the average
velocity and (ts) represents the total steps taken between 30-40m.
Average Step frequency could then be calculated:
Sf = v
Sl
Where (Sf) represents average step frequency, (v) is the average velocity and (Sl)
represents step length.
16
3.6 Data Analysis
All Statistical data was analysed using SPSS Statistics v.22 (IBM, USA) and all graphical
data was computed in Excel (Microsoft, USA). As sample size was <50, a Shapiro-Wilk
test of normality was applied to all descriptive statistics to determine if the data was
normally distributed (Villasenor Alva and Estrada, 2009).
The Participants best sprint trial was used for statistical analysis (Bevan et al., 2010). The
percentage difference between the control and potentiated 30-40m times and the
percentage difference between the Plyometric and Isometric SL and SF was calculated:
%change = (Control 30-40m – PAP 30-40m) x 100
PAP 30-40m
%change = (ISO SL or SF – PLYO SL or SF) x 100
PLYO SL OR SF
%change = (PLYO SL or SF – ISO SL or SF) x 100
ISO SL OR SF
Force data obtained from the force plate was exported in to an Excel spreadsheet
(Microsoft, USA) in which relative peak force values were calculated as:
Relative Peak Force = (F1- γ)
m
Where (F1) represents absolute peak force value, (γ) represents body weight and (m)
represents body mass. Due to corrupt data one of the subjects strength data could not be
computed and thus could not be utilised for data analysis.
A paired samples T-test was then used to test for any significant differences between the
%changes in 30-40m times. A Pearson’s correlation coefficient was used to correlate
relative peak force values against %change in 30-40m times, Plyometric SL and SF
%change and Isometric SL and SF %change. One way repeated-measures Analysis Of
Variance (ANOVA) were performed to analyse differences in 30-40m times, average step
length (SL) and average step frequency (SF). Post-hoc analysis consisted of a Bonferroni
correction (Armstrong, 2014). Where sphericity could not be assumed a GreenhouseGeisser correction was utilised (Garcia et al., 2008). For all statistical tests criterion for
statistical significance was set a priori of p< 0.05.
17
CHAPTER 4
RESULTS
18
4.0 Results
4.1 30-40m times
Repeated measures one-way ANOVA with Boferroni correction post hoc tests indicated no
significant differences between Plyometric (1.18 ± .083s) and Isometric (1.18 ± .092s) 3040m times F(1.396,16.752) = 4.67, p= 1.00 and Isometric (1.18 ± .092s) vs. Control (1.15
± .085s) 30-40m times (p= .064). A significant difference (p= .05) was observed between
Control and Plyometric 30-40m times. Figures 3 and 4 provide individual 30-40m times (s)
for Control and potentiated trials.
Figure 3: individual 30-40m time for Control and Plyometric PAP
Figure 4: individual 30-40m time for Control and Isometric PAP
19
4.2 Average Step Length
Repeated measures one-way ANOVA with Bonferroni correction post hoc test tests
revealed no significant differences between Control (1.61 ± .10m) vs. Plyometric (1.56 ±
0.12m) average step length F(2,24) = 3.170, p= .168, Control (1.61 ± .10m) vs. Isometric
(1.61 ± 0.11m) (p= 1.00) and Plyometric (1.56 ± 0.12m) vs. Isometric (1.61 ± 0.11m) (p=
.281). Figures 5 and 6 provide individual Step length responses to both PAP stimuli.
Figure 5: individual average Step length for Control and Plyometric PAP
Figure 6: individual average step length for Control and Isometric PAP
20
4.3 Average Step Frequency
Repeated measures one-way ANOVA with Bonferroni correction post hoc tests indicated
no significant difference between Control (5.42 ± .24 Hz) vs. Plyometric (5.48 ± .41 Hz)
F(2,24) = 3.055, p= 1.00 and Control (5.42 ± .24 Hz) vs. Isometric (5.29 ± .25 Hz) average
step frequency (p= .216). Differences in Plyometric (5.48 ± .41 Hz) vs. Isometric (5.29 ±
.25 Hz) average step frequency approached significance (p=0.53). Figures 7 and 8 provide
individual Step frequency responses to both PAP stimuli.
Figure 7: individual average Step Frequency for Control and Plyometric
PAP
Figure 8: individual average step Frequency for Control and Isometric PAP
21
4.4 Percentage change in 30-40m time
A paired samples T-test found no significant difference between the percentage change for
the Plyometric protocol (-2.67 ± 2.52%) and Isometric protocol (-2.66 ± 3.49%); t(12)= 0.006, p = .995. Negative values indicate slower 30-40m times, with positive values
representing decreases in 30-40m times. Figure 9 represents group differences for
Plyometric and Isometric PAP percentage changes.
Plyometric
Potentiation
Isometric
Potentiation
Figure 9: Differences between %change in 30-40m time for Plyometric and
Isometric PAP.
22
4.5 Plyometric PAP Step length and Step frequency relationship
Plyometric SL and SF were calculated as a percentage difference vs. Isometric SL and
SF. A Pearson’s correlation coefficient found a significant negative relationship between
the Plyometric step length (-3.04 ± 6.33%) and step frequency (3.46 ± 4.70%) percentage
change, r(11) = .732, p =0.004. Figure 10 represents the relationship between Plyometric
SF and SL %change.
Step Frequency (%change)
Step Length (%change)
Figure 10: Correlation between Plyometric SL and SF %change
23
4.6 Isometric PAP Step length and Step frequency relationship
Isometric SL and SF were calculated as a percentage difference vs. Plyometric SL and
SF. A Pearson’s correlation coefficient found a significant negative relationship between
the Isometric step length (3.53 ± 6.65%) and step frequency (-3.16 ± 4.40%) percentage
change, r(11) = .713, p =0.006. Figure 11 represents the relationship between Isometric
SF and SL %change.
Step Frequency (%change)
Step Length (%change)
Figure 11: Correlation between Isometric SL and SF %change
24
4.7 Relative Peak Force and Percentage change in 30-40m time
A Pearson’s correlation coefficient found no significant relationship between relative peak
force (23.14 ± 4.26 N/kg) and %change in Plyometric (-2.67 ± 2.52%) or Isometric (-2.66 ±
3.49%) 30-40m time, r(10) = -.290, p =0.360 and r(10) = -.190, p =0.553 respectively.
Negative values indicate slower 30-40m times vs. control, with positive values
representing decreases in 30-40m times. Figures 12 and 13 represent the relationship
between relative peak force and percentage change in 30-40m times for both potentiating
protocols.
Relative Peak Force (N/kg)
%Change in 30-40m time
Figure 12: Correlation between relative peak force and plyometric %change
Relative Peak Force (N/kg)
%Change in 30-40m time
Figure 13: Correlation between relative peak force and isometric %change
25
CHAPTER 5
DISCUSSION
26
5.0 Discussion
The present study investigated the potentiating effects of both plyometric and isometric
contractions on maximal velocity sprint performance. 3x 20 pogo jumps and 3x 5s
isometric mid-thigh pulls were utilised as potentiation stimuli to determine if different
contraction types had different effects on the maximal velocity phase of sprinting.
Kinematic data was analysed to determine if step length and frequency changes occurred
between the two protocols. Force data was also collected to see if a relationship exists
between relative peak force and the level of PAP. It was hypothesised that both the
isometric and plyometric protocols would have a PAP effect on maximal velocity, with the
plyometric conditioning activity (CA) having a greater PAP effect than the isometric
protocol.
5.1 Volume effects on PAP
Contrary to the initial hypothesis the main findings of the study was that both isometric and
plyometric protocols had negative effects on maximal velocity, with significantly worse 3040m times being observed between the plyometric protocol vs. control. The exact
mechanisms responsible for decreases in performance are unclear as no tests were used
to measure the level of neuromuscular activation (Mcbride, Nimphius and Errickson,
2005). In a recent meta-analysis in which 47 PAP studies were analysed Seitz and Haff
(2016) suggested that a plyometric CA would produce considerably larger PAP effects
than a maximal isometric CA, however the present study concludes that neither plyometric
or maximal isometric CAs have a PAP effect on sprint performance with performance
actually being decreased. It has be hypothesised that plyometric CAs may produce less
fatigue than traditional resistance exercise CAs (Seitz and Haff, 2016), Saez de Villarreal,
González-Badillo and Izquierdo (2007) reported greater PAP effects after 3 sets of 5
plyometric drop jumps than various squat protocols ranging from 2-4 reps of 80-95% of
1RM, however the difference was not significant and a countermovement jump (CMJ) was
used as the PAP measure. To date few studies have investigated plyometric CA vs.
isometric CA in relation to PAP in sprinting (Till and Cooke, 2009). Tsolakis et al. (2011)
investigated isometric (3x 3 seconds) vs. plyometric (3x 5 repetitions) PAP effect on lower
body (CMJ) explosive performance. The study found that the isometric CA had significant
negative effects on CMJ jump scores 8 and 12 minutes post-activation, with plyometric CA
having no effect. The present study however, suggests that the 3x 20 pogo hops
plyometric CA is a more fatiguing stimulus than the 3x 5 second isometric MTP 8 minutes
27
post-activation. Given the various intensities and volume utilised in previous plyometric
and isometric PAP studies (Till and Cooke, 2009; Tsolakis et al., 2011; Turner et al., 2015)
it is hard to identify the best protocol to elicit PAP. It is common in PAP literature that
generally multiple sets of a preconditioning activity induces a larger PAP effect (Wilson et
al., 2005; Chatzopoulos et al., 2007; Turner et al., 2015) than single set CAs (Till and
Cooke, 2009). However, the previous point is hard to confirm in relation to the present
findings with multiple sets being used and reporting decreases in maximal velocity sprint
performance. Moreover, the present study did not compare multiple sets vs. a single set
CA and it could be that other variables (i.e rest times, differing stimulus intensity/volume)
were the reason multiple sets were ineffective in this study (Tillin and Cooke, 2009). It was
hypothesised that the moderately sub-maximal pogo hops utilised would have provided a
biomechanically similar potentiation to the ankle kinematics observed at maximal velocity
(Wild et al., 2011), i.e. forefoot contact at high velocity with minimal changes in
dorsi/plantarflexion being observed in individuals with high levels of ankle stiffness
(Vanderka and Kampmiller, 2012). Turner et al. (2015) investigated two plyometric
protocols (bodyweight vs. weighted vest) of 3x 10 alternating leg bounds effects on 20m
sprint velocity. Both protocols had significant effects at 4 minutes post-activation, with the
weighted vest condition also having significant effects 8 minutes post-activation. The
volume prescribed was less than the present study, however given the added intensity of
the weighted vest, the differences in ground contact time of the plyometric exercise
(Turner et al., 2015) and acceleration phase as opposed to maximal velocity phase being
investigated, it makes study comparisons difficult. Previous sprinting PAP studies
investigating isometric CAs have utilised 3x 3 seconds of maximal isometric knee
extension and 3x 3 seconds of maximal isometric back squat and found no effect on 30m
sprint performance (Lim and Kong, 2013). Till and Cooke (2009) also found no effect after
3x 3 seconds of maximal isometric knee extension. The authors hypothesised that 9s of
maximal isometric contraction may not be enough to elicit a PAP response, however, the
previously discussed studies used a leg extension and isometric squat exercise as
opposed to the IMTP that the present study used. The isometric MTP and squat will recruit
more/different muscle groups (i.e. knee flexors, hip and leg extensors) than a single joint
isometric exercise (Garhammer, 1998), and thus provide a larger potentiating stimulus
(Tillin and Bishop, 2009) as a greater number of high order motor units would be recruited
(Tubman et al., 1996; Chiu et al., 2003) and potentially greater phosphorylation of myosin
regulatory light chains may occur (Grange, Vandenboom and Houston, 1993; Sale 2002;
Judge, 2009). However the IMTP and squat may cause greater fatigue (Garhammer,
28
1998), and given the coexistence of fatigue and potentiation (Xenofondos et al., 2010)
further research is warranted to investigate the prior hypothesis in relation to maximal
velocity sprinting.
It may simply be that the total of 60 plyometric contacts and 15s of maximal isometric
contraction, utilised in the present study, may be too great in volume prescription for
fatigue to have subsided 8 minutes post-activation in the subject population and PAP
effects may well have been observed after more rest (Tillin and Bishop, 2009). However
the present study did not investigate different rest intervals, volumes or different subject
populations.
5.2 Contraction Type effect on PAP
There currently exists minimal literature investigating different contraction types PAP effect
on sprint performance (Till and Cooke 2009; Lim and Kong, 2013), however both studies
investigated the acceleration phase of sprinting (>30m) (Wild et al., 2011). Lim and Kong
(2013) utilised both a single and multi-joint isometric CA vs. back squat, the study
concluded no significant differences between sprint trials vs. control and each other. Till
and Cooke (2009) utilised 5 tuck jumps as a plyometric stimulus vs. a single joint isometric
exercise and found no significant difference in sprint performance. Given that the back
squat and single joint isometric contractions were utilised it is difficult to compare study
findings. In relation to the multi-joint isometric CA (squat), conflicting findings were
observed in the present study; Lim and Kong (2013) reported non-significant increases in
performance whereas the present study observed non-significant decreases in
performance. In the 5 tuck jump protocol used in Till and Cooke (2009) no differences
were observed in sprint times. Seitz and Haff (2016) suggest that a plyometric CA may be
less fatiguing than loaded traditional exercises, such as the squat exercise, allowing a
greater potentiation effect to be achieved as less recovery time will be needed in order to
achieve the potentiated state, advocating that the PAP effect can be realized earlier after
the completion of a plyometric CA when compared with traditional high and moderateintensity CAs. However in coherence with the present findings, with 8 minutes rest being
utilised, it can be argued that more time would be needed after plyometric exercise before
the subsequent sprint trials in order for fatigue to subside and potentiation to occur (Rasier
and Macintosh, 2000; Tsolakis et al. 2011) given that previous research has found PAP
effects in sprint studies after 4 minutes with traditional CAs (Mcbride, Nimphius and
Errickson, 2005; Yetter and Moir, 2008; Till and Cooke, 2009). Given the high eccentric
forces involved with plyometric exercise and the high demand placed upon the
29
neuromuscular system when utilising the SSC (Harrison, Keane and Coglan, 2004), it is
unsurprising that subjects in the present study showed greater fatigue after the plyometric
CA than the isometric CA. Furthermore, it has been found that lactate accumulation occurs
at a faster rate during dynamic contractions as opposed to isometric contractions resulting
in faster peripheral and neuromuscular fatigue (Karelis, Marcil and Peronnet, 2004),
supporting the findings of the present study. Isometric contractions were reported to recruit
more muscle fibres than dynamic contractions, resulting in a greater percentage of
regulatory light chain phosphorylation and greater changes in muscle architecture (Tillin
and Bishop, 2009; Lim and Kong, 2013). Plyometric exercise has been associated with
preferential recruitment of type II motor units (Desmedt and Godaux, 1977), with
individuals with a higher percentage of type II fibres being shown to elicit a better PAP
response (Hamada et al., 2000). This occurs due to fast twitch fibres undergoing greater
phosphorylation of myosin regulatory light chains in response to a conditioning activity (Zhi
et al., 2005; Xenofondos et al., 2010). From the present study it can be concluded that a
plyometric PAP stimulus is more fatiguing than a maximal isometric stimulus, however as
observed in previous literature responses to both stimuli were highly individual (Sale,
2002; Till and Cooke, 2009; Linder et al., 2010; Lim and Kong, 2013). Some studies have
attributed differences in contraction type to strength levels (Till and Cooke, 2009; Lim and
Kong, 2013), however from the present data there is no evidence that individuals strength
levels dictates the PAP response following isometric or plyometric CAs. This study did not
recruit highly trained elite athletes who would be considered ‘strong’ such as utilised in
Nelson, McGuigan and Winchester (2008) in which mean absolute peak force values were
considerably higher than observed in the present study (2159±218 vs. 1852±372)
respectively.
5.3 Rest Period Effects on PAP
The rest interval between PAP and subsequent sprint trial may have played a role in the
present studies negative findings. Unlike the present study, Yetter and Moir (2008) and
Mcbride, Nimphius and Erickson (2005) both reported significant increases in 30-40m
times, however the squat exercise was used as the potentiation stimulus with differing
loads, volume and 4 minutes rest post-activation thus making the comparison between
results difficult. The subjects utilised and the subsequent rest time needed after the
potentiation stimulus has been shown to vary dependant on volume (Wilson et al. 2005),
contraction type (Lim and Kong, 2013) and muscle fibre type distribution (Sale et al.,
2002). The decrease in sprinting performance after 8 minutes may be explained by the
30
coexistence of fatigue and potentiation (Tsolakis et al. 2011). Following a pre-stimulus of
high intensity exercise, the muscle is both fatigued and potentiated and subsequent
muscular performance is dependent on these two factors and the rate of recovery
following the performance activity (Tillin and Bishop, 2009). It is possible that at 8 minutes
post-activation the fatigue effect was greater in both protocols than the potentiating effect,
thus subjects performed subsequent sprints under fatigued state as opposed to the
desired potentiated state. Long lasting fatigue after isometric exercise has been reported
previously (Hamada et al., 2003; Tsolakis et al. 2011), with studies utilising plyometric CAs
generally reported performance increases (Byrne, Kenny and O’Rourke, 2014; Turner et
al., 2015) or no significant effect (Till and Cooke, 2009). The latter point conflicts with the
findings of the present study. It is argued that a greater intensity and volume of PAP
contraction may result in the dominance of fatigue in the PAP-fatigue relationship (Tillin
and Bishop, 2009), this was potentially the case in the present study with both the
isometric and plyometric CA being greater in volume than previous sprinting PAP studies
(Till and Cooke, 2009; Byrne, Kenny and O’Rourke, 2014; Turner et al., 2015).
5.4 Subject strength levels and training age effect on PAP
Sprint speed controls observed in the present study were similar to that of Yetter and Moir
(2008) (8.75 ±0.69 m/s vs. 8.00 ±0.44 m/s) during the 30-40m split. Control 40m times
observed in the present study was similar to that of Mcbride, Nimphius and Erickson
(2005) (5.40 ±0.25 vs. 5.35 ±0.32). The previously mentioned studies are the only studies
that have looked at sprinting potentiation over 40m, as opposed to acceleration bias sprint
studies (Till and Cooke, 2009, Byrne, Kenny and O’ Rourke, 2014; Turner et al., 2015). 13
male mixed sports players were used in the present study and similar subject populations,
10 male mixed sports players and 15 male college level American football players
respectively, were utilised in the previous studies. Henceforth similarities in sprint
performance is not surprising (Chelly and Denis, 2001). The comparison of subject
characteristics is important as subject type has been shown to heavily influence the effect
of PAP (Ruben et al., 2010; Seitz and Haff, 2014).
It has been speculated that strength level of the individual mediates the PAP effect
experienced by differing volumes (Seitz and Haff, 2016). Stronger individuals have been
reported to respond better to single sets of very high intensity CAs (Seitz, L., de Villarreal,
E and Haff, G., 2014) as opposed to multiple sets (Ruben et al., 2010), weaker individuals
appear to elicit a better PAP response after multiple sets (Jo et al., 2010). A plausible
rationale for this phenomenon is that stronger individuals develop fatigue resistance to
31
heavier loads, and thus achieve a potentiated state faster as fatigue is minimised (Seitz
and Haff, 2016). It may be the case then that weaker individuals would require submaximal loads with greater volume and greater rest periods in order for PAP to be
experienced. Numerous studies support the argument that PAP effect is determined by
strength level (Ruben et al., 2010; Seitz, de Villarreal and Haff, 2014; Seitz, Trajano and
Haff, 2014), this may be attributed to stronger individuals having a greater percentage of
type II muscle fibres (Maughan, Watson, Weir, 1983; Aagaard and Andersen, 1998) and
thus greater phosphorylation of myosin light chain (Aagaard and Andersen, 1998; Tillin
and Bishop, 2009). Stronger individuals have also been reported to develop resistance to
heavier loads after a near-maximal effort potentially affecting the fatigue-potentiation
relationship post PAP stimulus (Chiu and Barnes, 2003). Moreover it has been reported
that individuals with a greater training age in relation to resistance training elicit a better
PAP response than those with a lower training age (Seitz and Haff, 2016). Generally this
would be expected given that highly trained individuals may have a greater number of type
II muscle fibres and therefore will elicit a better PAP response as previously discussed. In
the present study it was found that strength levels, determined by IMTP scores relative to
bodyweight, has no effect on the amount of PAP experienced. The authors hypothesise
that the nature of the sprint exercise is the reason no significant correlations were found
between PAP effect and strength. Previous PAP literature that has found that strength
levels determine the PAP effect (Ruben et al., 2010; Seitz, de Villarreal and Haff, 2014;
Seitz, Trajano and Haff, 2014) have used drop jumps and counter-movement jumps (CMJ)
as the PAP measure. In a CMJ the time for RFD is much greater (~0.6s) than at maximal
velocity sprinting (~0.18s) (Weyland et al., 2000; Linthorne, 2001), therefore stronger
individuals will develop greater ground reaction force in the given time thus creating
greater vertical displacement and jumping higher as a result (Till and Cooke, 2009).
However given the shorter duration of foot contact during the maximal velocity phase, the
time in which is available to generate ground reaction force is limited and therefore will
bias athletes of whom possess high levels of ankle stiffness and can apply large forces
quickly (i.e. highly trained sprinters) (Weyand et al., 2000). Given that the subjects utilised
were general athletic males of whom engaged in sport at differing levels, not specifically
sprinting,
it is highly possible that they did not possess the joint stiffness and
neuromuscular force producing capabilities that are required to efficiently perform at
maximal velocity (Kuitunen, Komi and Kyröläinen, 2002; Morin, Edouard and Samozino,
2011a). Morin, Edouard and Samozino (2011a) found that the index of force application
technique has a significant correlation with maximal velocity and therefore, any
32
musculotendinous potentiation that may have occurred from the PAP stimuli would
potentially not have been utilised effectively by the athletes as they did not possess the
ability to express force, the suitable structural adaptations or SSC efficiency (Wilson et al.,
2013).
5.5 Changes in Average step length and frequency
To date only one study found has investigated kinematic variables in relation to PAP
sprinting performance (Smith et al., 2014). However the study investigated the kinematic
changes in sprint performance whilst performing a resisted sprint with a sled at differing
loads as opposed to the changes in subsequent un-resisted sprint performance. The
present study found differing effects on SL and SF after the different contraction CAs. The
plyometric CA reduced SL, and given the inverse relationship between SL and SF, step
frequency was increased (Hunter et al., 2005). It has been reported that higher step
frequency resulting from a shorter contact time is a major determinant of sprint
performance success in relation to maximal velocity (Morin et al., 2012). Given the
significant decrease in maximal velocity performance and the increases in SF observed in
the present study, it is plausible to suggest that the subjects, due to their fatigued state,
were unable to exert greater force in the short periods of ground contact and thus adopted
an ineffective SF cadence as the ability to maintain SL via GRF was compromised
(Weyand et al., 2000). This hypothesis is in line with previous research in which
investigated fatigue over repeated sprints and found that in a fatigued state force
production was reduced and thus technical ability was altered (Morin et al., 2011b). The
opposite relationship between SL and SF was observed after the isometric potentiation, SL
was increased and thus SF decreased. It may be the case that the isometric CA increased
force producing properties; however subjects may have spent more time in contact with
the ground in order to produce the force in order to increase SL resulting in a greater
horizontal breaking force and therefore affecting sprint performance (Weyand et al., 2000;
Weyand et al., 2010). The previous hypotheses were not directly measured however and
thus in depth analysis of the kinematics involved would be needed to confirm the
presented hypotheses.
33
5.6 Limitations and Future Research
Future research should seek to investigate total isometric volumes between 9 and 15
seconds, and differing amounts of plyometric contacts (i.e. 5-60 contacts) at differing rest
intervals in order to establish the effects of differing volumes, rest intervals has when using
similar CAs to the present study in relation to maximal velocity sprinting. Although controls
were put in place for subject selection, 12 month active participation in sport with
resistance training incorporated into their training, the type of resistance training was not
specified. Therefore future research should carefully consider the subject population
utilised in relation to strength level when comparing differing contraction types in relation to
PAP. Henceforth, given the specificity to maximal velocity sprinting further studies should
utilise highly trained sprinters as they will be conditioned and thus variability in terms of
poor sprinting technique, structural adaptation and poor resistance to fatigue will be
minimised. Future research should also observe the effects of a similar protocol and its
potentiating effect on maximal velocity sprinting with in depth kinematic and kinetic
analysis of SL, SF and force changes that exist in relation to differing contraction CAs.
The present study utilised non-elite generally athletic males as opposed to elite sprinters
and as already discussed subject population will have a major effect on the PAP effect
experienced. Also the subjects best trial was utilised, therefore extra sprint trials may have
been performed after the conditioning activity with inter-sprint rest occuring and thus an
extra stimulus and greater recovery times may have skewed the results of the study (Tillin
and Bishop, 2009), however this approach has been used in previous PAP literature
(Mcbride, Nimphius and Errickson, 2005; Chatzopoulos et al., 2007; Till and Cooke, 2009;
Turner et al., 2015). The kinematic analysis was performed from 2 dimensional video data
captured, thus there is always the possibility of parallax error and given the relatively low
frame rate (50Hz) the exact frame at which the subject crossed the start line may have
been slightly inaccurate (Bartlett, 1997). The force plate data of which was utilised to
obtain force data relative to bodyweight was recorded in 20Hz as opposed to 1000Hz and
therefore maximal force data may have been inaccurate (Nelson, McGuigan and
Winchester, 2008).
34
CHAPTER 6
PRACTICAL APPLICATION AND CONCLUSIONS
35
6.0 Practical application and Conclusions
Although this study failed to show and significant PAP improvements on maximal velocity
sprint performance large individual variation in relation to the PAP stimuli existed. Given
the extensive transfer to many sports inclusive of sprinting, strength and conditioning
coaches looking to utilise PAP to enhance overall sprinting performance should examine
individual responses to PAP methods to establish if their athletes will respond positively.
Utilising PAP for sprint training sessions may be advocated providing that better
adaptations are observed with its use, however further research is warranted to confirm if
better adaptations occur when utilising PAP within training. Given the variability of PAP
stimuli used and subject populations utilised in present research, practitioners should
consider the differing factors involved such as contraction type, volume, intensity and
recovery times to fully benefit from PAP and its underpinning mechanisms. The present
protocol consisting of 3x 20 pogo hops or 3x 5 seconds of maximal IMTP should be
avoided in relation to potentiation of maximal velocity sprinting in males of whom would be
considered generally athletic, however future research is needed to establish the protocol
effects in elite populations. Given the small improvements that can be identified in
individual performance it seems that the benefits attributed to PAP should be reserved for
elite populations as time would be better spent developing general physical attributes in
non-elite individuals.
36
REFERENCES
37
References
Aagaard, P. and Andersen, J. (1998). Correlation between contractile strength and myosin
heavy chain isoform composition in human skeletal muscle. Medicine and Science in
Sports and Exercise, 30(8): 1217–22.
Aagaard, P., Simonsen, E., Andersen, J., Magnusson, P. and Dyhre-Poulsen, P. (2002).
Neural adaptations to resistance training: Evoked V-wave and H-reflex responses. Journal
Of Applied Physiology, 92: 2309–2318.
Abbate, F., Sargeant, A., Verdijk, P. and De Haan, A. (2000). Effects of high-frequency
initial pulses and post-tetanic potentiation on power output of skeletal muscle. Journal of
Applied Physiology, 88:35–40.
Alemdaroğlu, U. (2012). The Relationship Between Muscle Strength, Anaerobic
Performance, Agility, Sprint Ability and Vertical Jump Performance in Professional
Basketball Players. Journal of Human Kinetics, 31(1):87-92.
Arampatzis, A., Brüggemann, G. and Metzler, V. (1999). The effect of speed on leg
stiffness and joint kinetics in human running. Journal of Biomechanics. 32: 1349–1353.
Armstrong, R. (2014). When to use the Bonferroni correction. Ophthalmic And
Physiological Optics, 34(5), 502-508.
Baker, D. (2003). Acute effect of alternating heavy and light resistances on power output
during upper-body complex training. Journal of Strength and Conditioning
Research.17(3):493-497.
Barnes, K., Hopkins, W., McGuigan, M. and Kilding, A. (2015). Warm-up with a weighted
vest improves running performance via leg stiffness and running economy. Journal of
Science and Medicine in Sport, 18(1), 103-108.
Bartlett, R. (1997). Introduction to sports biomechanics. London: E & FN Spon.
Batista, M., Ugrinowitsch, C., Roschel, H., Lotufo, R., Ricard, M. and Tricoli, V. (2007).
Intermittent Exercise as a Conditioning Activity to Induce Postactivation Potentiation.
Journal of Strength and Condition Research, 21(3): 837–840.
38
Berning, J., Adams, K., DeBeliso, M., Sevene-Adams, P., Harris, C. and Stamford, B.
(2010). Effect of Functional Isometric Squats on Vertical Jump in Trained and Untrained
Men. Journal of Strength and Conditioning Research, 24(9): 2285-2289.
Bevan, H., Cunningham, D., Tooley, E., Owen, N., Cook, C., and Kilduff, L. (2010).
Influence of post-activation potentiation on sprinting performance in professional rugby
players. Journal of Strength and Conditioning Research, 24: 701–705.
Chatzopoulos, D., Michailidis, C., Giannakos, A., Alexiou, K., Patikas, D., Antonopoulos,
C., and Kotzamanidis, C. (2007). Postactivation potentiation effects after heavy resistance
exercise on running speed. Journal of Strength and Conditioning Research, 21: 1278–
1281.
Chelly, S. and Denis, C. (2001). Leg power and hopping stiffness: relationship with sprint
running performance. Medicine and Science in Sports and Exercise, 33(2): 326-333.
Chui, L., Fry, A., Weiss, L., Schilling, B. Brown, L. and Smith, S. (2003). Postactivation
potentiation response in athletic and recreationally trained individuals. Journal of Strength
and Conditioning Research, 17:671–677.
Comyns, T., Harrison, A., and Hennessy, L. (2010). Effect of squatting on sprinting
performance and repeated exposure to complex training in male rugby players. Journal of
Strength and Conditioning Research, 24: 610–618.
Cronin, J., Green, J., Levin, G., Brughelli, M., and Frost, D. (2007). Effect of Starting
Stance on Initial Sprint Performance. Journal Of Strength and Conditioning Research,
21(3), 990.
Desmedt, J. and Godaux, E. (1977). Ballistic contractions in man: characteristic
recruitment pattern of single motor units of the tibialis anterior muscle. Journal of
Physiology, 264(3): 673–93.
Docherty, D., Robbins, D., and Hodgson, M. (2004) Complex training revisited: A review of
its current status as a viable training approach. Strength and Conditioning Journal, 26: 5257.
Dolenec, A. and Čoh, M. (2009). Comparison of photocell and Optojump measurements of
maximum running velocity. Kinesiologia Slovenica, 15(2), 16–24.
39
Ebben W., and Petushek, E. (2010). Using the reactive strength index modified to evaluate
plyometric performance. Journal of Strength Conditioning Research, 24: 1983–1987.
Ebben, W. (2002) Complex training: A brief review. Journal of Sports Science and
Medicine, 1: 42-46.
Esformes, J., Keenan, M., Moody, J. and Bampouras, T. (2011). Effect of different types of
conditioning contraction on upper body postactivation potentiation. Journal of Strength and
Conditioning Research, 25: 143-148.
Faude, O., Koch, T. and Meyer, T. (2012). Straight sprinting is the most frequent action in
goal situations in professional football. Journal of Sports Sciences, 30(7), 625-631.
Foure, A., Nordez, A. and Cornu, C. (2010). Plyometric training effects on Achilles tendon
stiffness and dissipative properties. Journal of Applied Physiology, 109(3): 849-854.
Foure, A., Nordez, A. and Cornu, C. (2012). Plyometric training effects on Achilles
tendon stiffness and dissipative properties. European Journal of Applied Physiology,
112(8): 2849 – 2857.
Foure, A., Nordez, A., Guette, M. and Cornu, C. (2009). Effects of plyometric training on
passive stiffness of gastrocnemii and the musculo-articular complex of the ankle joint.
Scandinavian Journal of Medicine & Science in Sports, 19(6), 811-818.
French, D., Kraemer, W. and Cooke, C. (2003). Changes in dynamic exercise
performance following a sequence of preconditioning isometric muscle actions. Journal of
Strength and Conditioning Research, 17(4): 678–685.
Gago, P., Arndt, A., Tarassova, O. and Ekblom, M. (2014). Post activation potentiation can
be induced without impairing tendon stiffness. European Journal of Applied Physiology,
114(11): 2299-2308.
Garcia, P., Vallejo, G., Livacic-Rojas, P., Herrero, J. and Cuesta, M. (2008) Compative
robustness of six tests in repeated measures designs with specified departures from
sphericity. Quality and Quantity, 44(2), 289-301.
Glatthorn, J., Gouge, S., Nussbaumer, S., Stauffacher, S., Impellizzeri, F. and Maffiuletti,
N. (2011). Validity and Reliability of Optojump Photoelectric Cells for Estimating Vertical
Jump Height. Journal of Strength and Conditioning Research, 25(2), 556-560.
40
Goodwin, J. (2011). Maximum velocity is when we can no longer accelerate; using
biomechanics to inform speed development. The Journal of the UK Strength and
Conditioning Association, 21: 3-9.
Gossen, E., and Sale, D. (2000). Effect of postactivation potentiation on dynamic knee
extension performance. European Journal of Applied Physiology. 83: 524–530.
Gourgoulis, V., Aggelousis, N., Kasimatis, P., Mavromatis, G., and Garas, A. (2003). Effect
of the submaximal half-squats warm-up program on vertical jumping ability. Journal of
Strength and Conditioning Research, 17: 342–344.
Grange, R., Vandenboom, R. and Houston, M. (1993). Physiological Significance of
Myosin Phosphorylation in Skeletal Muscle. Canadian Journal of Applied Physiology,
18(3): 229-242.
Grant, M., Young, W. and Aitken, D. (2002). The acute effect of heavy loads on jump squat
performance: An evaluation of the complex and contrasting methods of power
development. Journal of Strength and Conditioning Research, 16: 530– 538.
Green, B.S., Blake, C. and Caulfield, B.M. (2010). A valid field test protocol of linear speed
and agility in rugby union. Journal of Strength and Conditioning Research 25, 1256-1262.
Gullich, A. and Schmidtbleicher, D. (1996). MVC-induced short-term potentiation of
explosive force. New Studies in Athletics, 11: 67–81.
Hamada, T., Sale D., MacDougall, J., Tarnopolsky, M. (2000). Postactivation Potentiation,
fiber type, and twitch contraction time in human knee extensor muscles. Journal of Applied
Physiology, 88:2131–2137.
Hamada, T., Sale, G., Macdougall, J. and Tarnopolsky, M. (2000). Postactivation
potentiation, fibre type, and twitch contraction time in human knee extensor muscles.
Journal of Applied Physiology, 88: 2131–2137.
Harrison, A., Keane, S. and Coglan, J. (2004). Force-Velocity Relationship and StretchShortening Cycle Function in Sprint and Endurance Athletes. Journal of Strength and
Conditioning Research, 18(3): 473–479
41
Hilfiker, R., Hubner, K., Lorenz, T., and Marti, B. (2007). Effects of drop jumps added to
the warm up of elite sport athletes with a high capacity for explosive development. Journal
of Strength and Conditioning Research, 21: 550–555.
Hodgson, M, Docherty, D, and Robbins, D. (2005) Post-activation potentiation: Underlying
physiology and implications for motor performance. Sports Medicine, 35: 585-595.
Hortobágyi, T., and P. Devita. (2000). Muscle pre- and coactivity during downward
stepping are associated with leg stiffness in aging. Journal of Electromyography and
Kinesiology, 10: 117–126.
Jensen, L., and Ebben, P. (2003). Kinetic analysis of complex training rest interval effect
on vertical Jump performance. Journal of Strength and Condition Research, 17: 345–349.
Jo, E., Judelson, D., Brown, L., Coburn, W. and Dabbs, C. (2010). Influence of recovery
duration after a potentiating stimulus on muscular power in recreationally trained
individuals. Journal of Strength and Conditioning Research, 24(2): 343–347.
Johnson, T., Brown, L., Coburn, J., Judelson, D., Khamoui, A., Tran, T. and Uribe, B.
(2010). Effect of Four Different Starting Stances on Sprint Time in Collegiate Volleyball
Players. Journal of Strength And Conditioning Research, 24(10), 2641-2646.
Jones, P. and Lees, A. (2003). A biomechanical analysis of the acute effects of complex
training using lower limb exercises. Journal of Strength and Condition Research, 17: 694–
700.
Judge, L. (2009). The Application of Postactivation Potentiation to the Track and Field
Thrower. Strength and Conditioning Journal, 31(3): 34-36.
Karelis, A., Marcil, M, and Peronnet, F. (2004) Effect of lactate infusion on M-wave
characteristics and force in the rat plantaris muscle during repeated stimulation in situ.
Journal of Applied Physiology,96: 2133–2138.
Kawamori, N., Rossi, S., Justice, B., Haff, E., Pistilli, E., O'Bryant, H., Stone, M. and Haff,
G. (2006). Peak Force and Rate of Force Development During Isometric and Dynamic
Mid-Thigh Clean Pulls Performed at Various Intensities. Journal of Strength and Condition
Research, 20(3), 483-491.
42
Kay, A. and Blazevich, A. (2009). Isometric contractions reduce plantar flexor moment,
Achilles tendon stiffness, and neuromuscular activity but remove the subsequent effects of
stretch. Journal of Applied Physiology, 107(4): 1181-1189.
Kilduff, L., Bevan, H., Kingsley, M., Owen, N., Bennett, M., Bunce, P., Hore, A., Maw, J.
and Cunningham, D. (2007). Postactivation Potentiation in Professional Rugby Players:
Optimal Recovery. Journal of Strength and Condition Research, 21(4), 1134.
Kuitunen, S., Komi, P. and Kryöläinen, H. (2002). Knee and ankle joint stiffness in sprint
running. Medicine & Science in Sports & Exercise, 34(1), 166-173.
Kuitunen, S., Komi, P. and Kyröläinen, H. (2002). Knee and ankle joint stiffness in sprint
running. Medicine and Science in Sports and Exercise, 34(1): 166-173.
Linder, E., Prins, J., Murata, N., Derenne, C, Morgan, C. and Solomon, J. (2010). Effects
of preload 4 repetition maximum on 100-m sprint times in collegiate women. Journal of
Strength and Condition Research, 24: 1184–1190,
Linthorne, N. (2001). Analysis of standing vertical jumps using a force platform. American
Journal of Sports Physiology, 69(11): 1198.
Lorenz, D. (2011). Postactivation Potentiation: An introduction. International Journal of
Sports Physical Therapy, 6(3):234-240.
Macintosh, B. and Willis, J. (2000). Force-frequency relationship and potentiation in
mammalian skeletal muscle. Journal of Applied Physiology, 88: 2088–2096.
Mann, R. and Hagy, J. (1980). Biomechanics of walking, running, and sprinting. The
American Journal of Sports Medicine, 8(5): 345-350.
Masamoto, N., Larson, R., Gates, T. and Faigenbaum. A. (2003). Acute effects of
plyometric exercise on maximum squat performance in male athletes. Journal of Strength
and Conditioning Research, 17: 68–71.
Maughan, R., Watson, J. and Weir, J. (1983). Relationships between muscle strength and
muscle cross-sectional area in male sprinters and endurance runners. European Journal
of Applied Physiology, 50(3): 309–318.
43
McBride, J., Nimphus, S. and Erickson, T. (2005). The acute effects of heavy load squats
and loaded countermovement jumps on sprint performance. Journal of Strength and
Condition Research, 19: 893–897.
Morin, J., Bourdin, M., Edouard, P., Peyrot, N., Samozino, P. and Lacour, J. (2012).
Mechanical determinants of 100-m sprint running performance. European Journal of
Applied Physiology, 112(11), 3921-3930.
Morin, J., Edouard, P. and Samozino, P. (2011a). Technical ability of force application as a
determinant factor of sprint performance. Medicine and Science in Sports and Exercise,
43: 1680-1688
Morin, J., Samozino, P., Edouard, P., and Tomazin, K. (2011b). Effect of fatigue on force
production and force application technique during repeated sprints. Journal of
Biomechanics, 44: 2719-2723.
Oliver, J.L. and Meyers, R.W. (2009) Reliability and generality of measures of
acceleration, planned agility, and reactive agility. International Journal of Sports
Physiology and Performance, 4:345-354.
Pruyn, E., Watsford, M. and Murphy, A. (2014). The relationship between lower-body
stiffness and dynamic performance. Applied Physiology, Nutrition, and Metabolism, 39(10):
1144-1150.
Radcliffe, J. and Radcliffe, J. (1996). Effects of different warm-up protocols on peak power
output during a single response jump task. Medicine and Science in Sports Exercise,
28(5): 189.
Rahimi, R. (2007). The acute effect of heavy versus light-load squats on sprint
performance. Physical Education and Sport, 5: 163–169.
Rasier, D., and B. Macintosh. (2000). Coexistence of potentiation and fatiguein skeletal
muscle. Brazilian Journal of Medical and Biological Research, 33: 499–508.
Ruben, R., Molinari, M., Bibbee, C., Childress, M., Harman, M., Reed, K. and Haff, G.
(2010). The Acute Effects of An Ascending Squat Protocol on Performance During
Horizontal Plyometric Jumps. Journal Of Strength And Conditioning Research, 24(2), 358369.
44
Ruben, R., Molinari, M., Bibbee, C., Childress, M., Harman, M., Reed, K. and Haff, G
(2010). The acute effects of an ascending squat protocol on performance during horizontal
plyometric jumps. Journal of Strength and Conditioning Research, 24(2): 358–69.
Saez de Villarreal, E., González-Badillo, J. and Izquierdo, M. (2007). Optimal warm-up
stimuli of muscle activation to enhance short and long-term acute jumping performance.
European Journal of Applied Physiology, 100(4): 393-401.
Sale, D. (2002). Postactivation potentiation: Role in human performance. Exercise and
Sport Science Review. 30(3):138–143.
Sapstead, G. and Duncan, M. (2013). Acute effect of isometric mid-thigh pulls on
Postactivation Potentiation during stretch-shortening cycle and non-stretch shortening
cycle vertical jumps. Medicina Sportiva: 17(1): 7-11.
Schache, A., Dorn, T., Blanch, P., Brown, N. and Pandy, M. (2012). Mechanics of the
Human Hamstring Muscles during Sprinting. Medicine and Science in Sports and
Exercise, 44(4), 647-658.
Schneiker, K., Bishop, D., Dawson, B. and Hackett, L. (2006). Effects of Caffeine on
Prolonged Intermittent-Sprint Ability in Team-Sport Athletes. Medicine and Science in
Sports & Exercise, 38(3): 578-585.
Scott, S. and Docherty, D. (2004). Acute effects of heavy preloading on vertical and
horizontal jump performance. Journal of Strength and Conditioning Research. 18(2): 201–
205.
Seitz, L. and Haff, G. (2015). Application of Methods of Inducing Postactivation
Potentiation during the Preparation of Rugby Players. Strength and Conditioning Journal,
37(1): 40-49.
Seitz, L. and Haff, G. (2016). Factors Modulating Post-Activation Potentiation of Jump,
Sprint, Throw, and Upper-Body Ballistic Performances: A Systematic Review with MetaAnalysis. Sports Medicine, 46(2): 231-240.
Seitz, L., de Villarreal, E. and Haff, G. (2014). The temporal profile of postactivation
potentiation is related to strength level. Journal of Strength and Conditioning Research,
28(3): 706–715.
45
Shorten, M. (1987). Muscle elasticity and human performance. Medicine and Sport
Science, 25: 1–18.
Smith, C., Hannon, J., McGladrey, B., Shultz, B., Eisenman, P. and Lyons, B. (2014). The
effects of a postactivation potentiation warm-up on subsequent sprint performance. Human
Movement, 15(1): 36-44.
Stone, M., Sands, W., Pierce, K., Ramsey, M. and Haff, G. (2008). Power and power
potentiation among strength-power athletes: Preliminary study. International Journal of
Sports Physiology Performance, 3: 55–67.
Till, K. and Cooke, C. (2009). The Effects of Postactivation Potentiation on Sprint and
Jump Performance of Male Academy Soccer Players. Journal of Strength and
Conditioning Research, 23(7): 1960-1967.
Tillin, N., and Bishop, D. (2009). Factors modulating post-activation potentiation and its
effect on performance of subsequent explosive activities. Sports Medicine, 39: 147–166.
Trimble, M., and Harp, S. (1998). Post-exercise potentiation of the H-reflex in humans.
Medicine and Science in Sports and Exercise, 36: 993–941.
Tsolakis, C., Bogdanis, G., Nikolaou, A. and Zacharogiannis, E. (2011) Influence of type of
muscle contraction and gender on postactivation potentiation of upper and lower limb
explosive performance in elite fencers. Journal of Sports Science and Medicine, 10: 577583.
Turner, A., Bellhouse, S., Kilduff, L. and Russell, M. (2015). Postactivation Potentiation of
Sprint Acceleration Performance Using Plyometric Exercise. Journal of Strength and
Conditioning Research, 29(2): 343-350.
Vandenboom, R., Grange, R., and Houston, M. (1995). Myosin phosphorylation enhances
rate of force development in fast-twitch skeletal muscle. American Journal of Physiology,
268: 596–603.
Vanderka, M. and Kampmiller, T. (2012). Ontogenetic Development of Kinematic
Parameters of the Running Stride. Sport Science Review, 20(3): 5-24.
Vandervoort, A., Quinlin, J. and McComas, A. (1983). Twitch potentiation after voluntary
contraction. Experimental Neurology, 81:141–152.
46
Viitasalo, J.T., Luhtanen, P., Mononen, H.V., Norvapalo, K., Paavolainen, L. and Salonen,
M. (1997). Photocell Contact Mat: A New Instrument to Measure Contact and Flight Times
in Running. Journal of Applied Biomechanics, 13(2): 254–266.
Weir, J. (2005). Quantifying Test-Retest Reliability Using the Intraclass Correlation
Coefficient and the SEM. Journal Of Strength and Conditioning Research, 19(1): 231.
Weyand, P., Sternlight, D., Bellizzi, M. and Wright, S. (2000). Faster top
running speeds are achieved with greater ground forces not more rapid leg movements.
Journal of Applied Physiology, 89: 1991--‐1999.
Whelan, N., O'Regan, C., and Harrison, A. (2014). Resisted sprints do not acutely
enhance sprinting performance. Journal of Strength & Conditioning Research. 28:18581866.
Wild, J., Bezodis, N., Blagrove, R. and Bezodis, I. (2011). A Biomechanical comparison of
accelerative and maximum velocity sprinting: specific strength training considerations. The
Journal of the UK Strength and Conditioning Association, 21: 23‐36.
Wilson, J., Duncan, N., Marin, P., Brown, L., Loenneke, J., Wilson, S., Jo, E., Lowery, R.
and Ugrinowitsch, C. (2013). Meta-Analysis of Postactivation Potentiation and Power.
Journal of Strength and Conditioning Research, 27(3): 854-859.
Wilson, J., Duncan, N., Marin, P., Brown, L., Loenneke, J., Wilson, S., Jo, E., Lowery, R.
and Ugrinowitsch, C. (2013). Meta-Analysis of Postactivation Potentiation and Power.
Journal of Strength and Conditioning Research, 27(3): 854-859.
Winchester, J., Nelson, A., Landin, D., Young, M. and Schexnayder, I. (2008). Static
Stretching Impairs Sprint Performance in Collegiate Track and Field Athletes. Journal of
Strength and Conditioning Research, 22(1), 13-19.
Winwood, P., Posthumus, L., Cronin, J., Keogh, J. (2015). The Acute Potentiating Effects
of Heavy Sled Pulls on Sprint Performance. Journal of Strength and Conditioning
Research, [Epub ahead of print].
Xenofondos, A., Laparidis, K., Kyranoudis, A., Galazoulas, C., Bassa, E., Kotzamanidis, C.
(2010). Postactivation potentiation: Factors affecting it and the effect on performance.
Journal Of Physical Education and Sport, 28(3): 32-38.
47
Yetter, M. and Moir, G. (2008). The acute effects of heavy back and front squat on speed
during forty-meter sprint trails. Journal of Strength and Conditioning Research,22: 159–
165.
Young, W., Jenner, A. and K. Griffiths. (1998). Acute enhancement of power performance
from heavy load squats. Journal of Strength and Conditioning Research, 12: 82–84.
Young, W., McLean, B. and Ardagna, J. (1995). Relationship between strength qualities
and sprinting performance. Journal of Sports Medicine Physical Fitness, 35: 13– 19.
Zhi, G., Ryder, J., Huang, J., Ding, P., Chen, Y., Zhao, Y., Kamm, K. and Stull, J. (2005).
Myosin light chain kinase and myosin phosphorylation effect frequency-dependent
potentiation of skeletal muscle contraction. Proceedings of the National Academy of
Sciences of the USA, 102(48): 1751–1752.
48
APPENDICIES
APPENDIX A
PARTICIPANT INFORMATION SHEET
A-1
Isometric Mid-thigh pull vs Plyometrics Post Activation Potentiation effect on
maximum velocity.
Participation Information Sheet
Background
This study will investigate and gain relevant information regarding the use of pre-sprint exercises to enhance
subsequent sprint performance. There remains huge debate on the best exercises and rest periods to use in
order to get enhanced sprint performance, therefore this study will utilise previous research published to
further aid in concluding the best exercises and rest periods for enhancing sprint performance. In order to
gather data you will have to attend testing on three occasions, consisting of a control trial and two separate
pre-sprint intervention days. Testing will be spread over a four week period
Why have you been asked?
You have been asked as we believe you would be of benefit from participating. You would gain sprint times
and potential ways of increasing your performance.
What would happen if you agree to take part?
If you agree to join the study, there are three main things that will happen.
1. You will attend testing sessions three times, on three separate occasions, spread out over roughly
one month.
2. During each trial day you will undergo either a control trial or one of two pre-sprint intervention days.
3. The control trial day will consist of performing a standardised warm up, involving some light jogging,
stretching and short sprints. You will then get four minutes rest, followed by three 45m sprint trials
separated by four minutes rest.
4. One of the pre-sprint intervention days will consist of performing a standardised warm up, involving
some light jogging, stretching and short sprints. You will then have to perform a 5s maximal
contraction against a fixed bar at mid-thigh level. Eight minutes passive rest involving walking to
main body temperature will then occur. After the eight minutes of rest you will perform three 45m
sprints separated by 4 minutes rest.
5. The other pre-sprint intervention day will consist of performing a standardised warm up, involving
some light jogging, stretching and short sprints. You will then have to perform three sets of 20
plyometric hopss separated by a short rest. Eight minutes passive rest involving walking to main
body temperature will then occur. After the eight minutes of rest you will perform three 45m sprints
separated by 4 minutes rest.
6. After testing has taken part we will analyse the data in computer software to draw upon conclusions
from the study, your personal scores can be given to you if you wish.
Are there any risks?
Although unlikely, risks from taking part with the study can involve potential injury from added training
volume and/or traumatic injury. Other risks could potentially involve injury from improperly set up equipment
or equipment malfunction. Otherwise general risks are considered to be significantly low.
What happens to the results of the evaluation?
All of the subjects will simply be labelled in coded manor, in which absolutely no personal details will be
disclosed. Absolutely no address details or details concerning personal matters will be disclosed. Your age,
height a weight however will be used calculate the populations mean for each variable. The sprint trial scores
will be analysed and the fastest times will be used in data analysis to compare differences across all three
trials and testing days.
A-2
Are there any benefits from taking part?
Yes, hopefully you will about sprinting data collection procedures and exercises and warm-ups that can be
used prior to a sprinting session. This study should hopefully give an indication for you on what part of your
sprint needs to be worked on and potential methods to go about improving sprint performance.
What happens next?
After you read this information sheet we would require you to fill out a consent form to indicate you are happy
to participate in the study. We will then hopefully be seeing you for testing.
How we protect your privacy:
As specified you can see that we will take every step to ensure your privacy is protected in accordance with
privacy and confidentiality laws and guidelines.
The information collected before, during and after the testing days will be filed away securely and once the
relevant information has been gathered and used to statistical analysis, will be stored away in an archive
safely and securely. Only those involved will be able to gain access to the information collected.
We will only ask for your name, age, height and weight.
Further information
If any further questions you wished to be answered about the experimental study, please contact us via the
following:
Mr Louie P. Sims
Head Researcher
07792874894
@outlook.cardiffmet.ac.uk
A-3
APPENDIX B
PARTICIPANT CONSENT FORM
B-1
PARTICIPANT CONSENT FORM
Reference Number: MTPVSPLYO2015
Participant name or Study ID Number:
Title of Project: Isometric Mid-thigh pull vs Plyometrics Post Activation Potentiation effect on
maximum velocity.
Name of Researcher: Louie Sims
___________________________________________________________________
Participant to complete this section:
Please initial each box.
1.
I confirm that I have read and understand the information sheet for the
above study. I have had the opportunity to consider the information, ask
questions and have had these answered satisfactorily.
2.
I understand that my participation is voluntary and that I am free to
withdraw at any time, without giving any reason.
3.
I agree to take part in the above study.
_______________________________________ ___________________
Signature of Participant
_______________________________________ ___________________
Name of person taking consent
Date
____________________________________
Signature of person taking consent
* When completed, 1 copy for participant & 1 copy for researcher site file
B-2
APPENDIX C
PAR-Q
C-1
C-2