Calcif Tissue Int
DOI 10.1007/s00223-015-9976-6
ORIGINAL RESEARCH
Low-Load Very High-Repetition Resistance Training Attenuates
Bone Loss at the Lumbar Spine in Active Post-menopausal
Women
Vaughan P. Nicholson • Mark R. McKean •
Gary J. Slater • Ava Kerr • Brendan J. Burkett
Received: 7 November 2014 / Accepted: 27 February 2015
Ó Springer Science+Business Media New York 2015
Abstract This study determined the effect of 6 months of
low-load very high-repetition resistance training on bone
mineral density (BMD) and body composition in nonosteoporotic middle-aged and older women. Fifty healthy,
active community-dwelling women aged 56–75 years took
part in the two-group, repeated-measures randomized
controlled trial. Participants either undertook 6 months of
low-load very high-repetition resistance training in the
form of BodyPumpTM or served as control participants.
Outcome measures included BMD at the lumbar spine, hip,
and total body; total fat mass; fat-free soft tissue mass and
maximal isotonic strength. Significant group-by-time interactions were found for lumbar spine BMD and maximal
strength in favor of the BodyPumpTM group. No favorable
effects were found for hip BMD, total body BMD, total fat
mass, or fat-free soft tissue mass. Three participants
withdrew from the intervention group due to injury or fear
of injury associated with training. Under the conditions
used in this research, low-load very high-repetition resistance training is effective at attenuating losses in lumbar
spine BMD compared to controls in healthy, active women
aged over 55 years but did not influence hip and total body
BMD or fat mass and fat-free soft tissue mass.
Keywords Bone mass Exercise Strength Middle-age Elderly
V. P. Nicholson (&) M. R. McKean G. J. Slater A. Kerr B. J. Burkett
School of Health and Sport Sciences, University of the Sunshine
Coast, 90 Sippy Downs Drive, Sippy Downs, QLD 4556,
Australia
e-mail: [email protected]
Introduction
Age-related reductions in bone mineral density (BMD)
occur at most skeletal sites after the third or fourth decade
in men and women [1] and such reductions are typically
accelerated in women after menopause [2, 3]. Fortunately,
it is now well established that resistance training can
maintain and improve BMD in post-menopausal women
[4–6]. Typically, high-intensity (or high-load) training interventions utilizing training loads over 75–80 % of onerepetition maximum (1RM) have been more successful at
improving BMD when compared to low-load training
(\50 % 1RM) interventions [7, 8], though the low-load
interventions assessed have also used relatively low
repetition ranges. Interestingly, when training volumes are
equivalent both the low- and high-load training may be
similarly effective at improving BMD [5].
Low-load high-repetition resistance training has been
shown to improve maximal strength, balance, and functional task performance in older populations [9, 10] but to
date there has been no research exploring its effect on
BMD when very low loads (\30 % 1RM) and very high
repetitions ([60) are used. Animal bone loading experiments have demonstrated that increasing repetitions at
submaximal loads increases the bone response compared
with low repetitions [11, 12] suggesting that high cycle
numbers compensate for low strain magnitudes. Additionally, low-load high-repetition training with vascular restriction produces similar changes in markers of bone
turnover as high-load training [13]. As such, low-load very
high-repetition ([60 repetitions) resistance training may
provide an alternative to high-load resistance training in
middle-aged and older adults. Moreover, low-load very
high-repetition resistance programs such as BodyPumpTM
are available in over 14,000 fitness facilities globally [14].
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V. P. Nicholson et al.: Bone density and low-load very high repetition resistance training
This pre-choreographed group class uses light weights and
very high (80–100) repetitions for each exercise so it
provides a platform to assess the effect of low-load very
high-repetition resistance training and as recent trends
indicate that a growing number of over 55 s are undertaking fitness center-based activities [15], the apparent effectiveness of such activities warrants examination.
Furthermore, social factors are a key motivator for exercise
participation in middle-aged and older adults [16] so participation in a group class may promote greater compliance
among participants and provide prolonged benefits.
The aim of this study was to assess whether 6 months of
low-load very high-repetition resistance training in the
form of BodyPumpTM would improve BMD and fat-free
soft tissue mass in a group of healthy, active females aged
over 55 years. It was hypothesized that BMD at the lumbar
spine and hip would be better preserved in the intervention
group compared with the control group and that fat-free
soft tissue mass would increase after 6 months of group
training. Additionally it was hypothesized that maximal
dynamic strength would increase following such an
intervention.
Methods
Participants
Apparently healthy women aged between 55 and 75 years
were invited to take part in the study. All participants were
recruited through local advertising and an adult education
facility. All participants were physically active non-fallers
who had not undertaken formal resistance training in the
previous year. All women were at least 5 years postmenopause and provided details of medical history and
current medication use. Exclusion criteria included: acute
or terminal illness, myocardial infarction in the past
6 months, recent low impact fracture, osteoporosis, use of
hormone replacement therapy (HRT), and other medications known to affect bone metabolism in the previous
2 years, or any condition that would interfere with moderate intensity exercise participation. A total of 50 women
aged 58–75 years took part in the intervention after providing informed consent conforming to the Declaration of
Helsinki, approved by the Human Research Ethics Committee of the university.
size of 25 per group to identify an expected difference of
1 % between groups for lumbar spine BMD with a standard
deviation of 0.1 g/cm2 [4, 8]. To account for a 15 % attrition rate a sample size of 29 per group was required.
Participants undertook all testing at university testing facilities at baseline and after 6 months. Participants were
allocated to either the intervention group (PUMP) or control group (CON) on a 1:1 ratio using a computer-generated
random number list after baseline data collection.
PUMP participants were instructed to attend two
BodyPumpTM classes per week for 6 months. Each class
was approximately 50 min in duration and included exercises such as squats, lunges, and chest press, utilizing light
weights and a very high number of repetitions. BodyPumpTM release 83 was used for the duration of the program (Table 1). The pre-choreographed class is separated
into ten tracks that last up to 6 min each. Each track focuses on a particular movement pattern such as squats or a
particular muscle group such as biceps or triceps. All
classes were conducted at a local fitness facility where
PUMP participants were provided with complimentary
access. Classes were exclusively attended by project participants and all classes were instructed by experienced
group fitness instructors who were not associated with
testing or recruitment of participants. The first 4 weeks of
the intervention were used to ensure if participants completed all exercises with appropriate technique. From week
5 onwards all classes were instructed at a level that one
would expect to encounter if they took part in a BodyPumpTM class at any fitness center providing such classes.
The weights lifted for each exercise were self-selected but
were guided by general recommendations provided by the
class instructor. Participants recorded the weight lifted for
the selected exercises during each session and these records
were later used to determine changes in load over the
course of the program (Table 2). Control (CON) participants did not undergo any training and were instructed
to maintain their current level of physical activity for the
duration of the study.
Measurements
Participants were tested on two occasions: the first
assessment was conducted prior to the beginning of training and the second assessment was conducted immediately
after the 6-month intervention.
Study Design and Intervention
Body composition
A two-group, repeated-measures, randomized control trial
was used to investigate the effects of 6 months of BodyPumpTM training. A priori power calculation with power
set at 0.8 and an alpha of 0.05 identified a required sample
Body composition assessments were performed using dualenergy X-ray absorptiometry (DXA). Participants were
overnight fasted and had not undergone any exercise in the
morning before measurements. Participants wore light
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V. P. Nicholson et al.: Bone density and low-load very high repetition resistance training
Table 1 General characteristics
of a BodyPumpTM session
(release 83)
Track number—name
1—Warm up
6
Upright row to overhead press
4
Overhead press
16
Squats
4
8 (per leg)
2—Squats
Squats
108
3—Chest
Chest press
94
4—Back
Dead row
41
Dead lift
15
Clean & press
12
Power press
7
Triceps extension
22
Triceps press
Standing overhead extension
52
30
6—Biceps
Bicep curl
68
7—Lunges
Squat
50
10—Cool down
Squat
Chest press
2.9 ± 1.9 kg
5.5 ± 3.9 kg
2.6 ± 1.1 kg
4.6 ± 5.2 kg
Mean weight ± SD week 13
8.0 ± 3.1 kg
5.6 ± 4.2 kg
Mean weight ± SD week 26
8.2 ± 3.1 kg
6.0 ± 4.4 kg
% 1RM ± SD week 1
3.7 ± 2.2 %
11.8 ± 6.3 %
% 1RM ± SD week 5
7.0 ± 2.7 %a
20.7 ± 9.2 %c
10.0 ± 3.6 %
a,b
24.8 ± 10.1 %c
10.6 ± 3.8 %
a,b
27.4 ± 9.9 %c
Significantly (p \ 0.001) more than week 1
b
Significantly (p \ 0.05) more than week 5
c
Significantly (p \ 0.05) more than week 1
Jump squat
16
Pulse jump squat
16
Lunge
25 (per leg)
Push-up
36
Standing rear deltoid raise
8
Standing side raise
18
Upright row
8
Overhead press
16
Crunch
40
Hover
14
Stretch/mobility
Table 2 Weights used for squats and chest press during the 6-month
training intervention
a
24
16
9—Core
% 1RM ± SD week 26
Deadlift
Dead row
Bicep curl
8—Shoulders
% 1RM ± SD week 13
Approximate repetitions
Lunges
5—Triceps
Mean weight ± SD week 1
Mean weight ± SD week 5
Exercise
sports clothes with all jewelery and metal objects removed
before each scan. Body weight was measured to the nearest
0.1 kg on electronic scales (Tanita, Japan) and body height
was assessed by a wall-mounted stadiometer to the nearest
0.001 m (Table 3).
BMD of the lumbar spine (anteroposterior L2–4) and
hip (femoral neck, total hip, and trochanter) were assessed
following the established protocols using pencil beam
DXA (Lunar DPX Pro, GE Healthcare, UK) with analysis
performed using enCoreTM software (GE Healthcare, UK).
Total body BMD, fat mass, and fat-free soft tissue mass
were assessed by a whole-body scan. The DXA was
calibrated with phantoms as per the manufacturer’s
guidelines each day before measurement. The short-term
coefficient of variance (CV) for BMD and body composition in our laboratory ranged from 0.5 to 1.5 % and 0.6 to
2.2 %, respectively. For the whole-body scan, the scanning
mode was automatically chosen by the DXA machine with
scans for all but two participants (thick mode) scanned in
the standard mode. Subjects were centrally aligned in the
scanning area for all scans. All scans were performed and
analyzed by a single trained and licensed technician who
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V. P. Nicholson et al.: Bone density and low-load very high repetition resistance training
Table 3 Baseline participant
characteristics
Pump (N = 28)
Control (N = 29)
Age (years)
66.0 ± 4.1
65.6 ± 4.7
Height (cm)
164.4 ± 4.4
163.3 ± 5.5
Values reported as mean ± SD
Weight (kg)a
70.6 ± 9.1
66.8 ± 10.7
a
BMI (kg/m2)
26.0 ± 3.2
24.5 ± 2.9
1.5 ± 1.5
1.3 ± 1.1
Significant difference
(p \ 0.05) between groups at
baseline
Number of prescribed medications
was blinded to group allocation. The scans were analyzed
automatically by the software but regions of interest were
subsequently confirmed by the technician.
Strength, Diet, and Activity Assessment
Assessment of 1RM was conducted for the incline leg press
(Calgym, Australia) and Smith machine bench press (Elite,
Australia). A familiarization session was held approximately 1 week prior to baseline 1RM testing to ensure
correct lifting technique using submaximal loads. Testing
using established protocols [17] commenced after a light
cycling warm-up with leg press assessed prior to Smith
machine bench press. Squat 1RM was subsequently predicted from the leg press assessment [18] and the amount
of weight lifted during the program was monitored for both
squats and chest press.
Dietary intake was assessed from self-reported 3-day
food records completed at baseline and follow-up. Participants were instructed to record the type and amount of
all food, drink, and supplements consumed over three
consecutive days (2 week days and 1 weekend day). All
records were entered into FoodWorks 7 (Xyris Software,
Australia) and daily consumption of total energy (kJ),
protein (g/kg body weight), and calcium (mg) were analyzed. Energy expenditure derived from exercise and
physical activity was estimated by a 7-day activity diary. A
metabolic equivalent value was assigned to each activity
and was used to determine the average amount of energy
used for exercise/planned physical activity (including
BodyPump classes) during the program for both groups
[19].
Statistical Analyses
All data are reported as mean and standard deviation (SD).
Primary outcomes were changes from baseline in BMD, fat
mass, and fat-free soft tissue mass in response to the
6-month intervention. Secondary outcomes included
6-month changes from baseline in maximal strength, dietary intake, energy expenditure, and changes in weight
lifted during each class during the PUMP intervention.
Potential differences between groups at baseline were
assessed by independent t tests. A repeated-measures
123
general linear model (GLM) was used to determine group
(PUMP, CON) and time (baseline, 6 months) effects on
primary outcomes. Baseline values for any measures that
were different between groups at baseline were used as a
covariate in the GLM. Partial eta squared was used to
determine the effective size for each outcome variable.
When the GLM revealed significant interaction (time 9
group), paired samples t tests were used to assess differences between initial and final values for each group. A
repeated-measures ANOVA with pairwise comparisons
and Bonferroni correction was used to determine differences between the amounts of weight lifted (in terms of
percentage 1RM) for squats and chest press at four time
points (week 1, week 5, week 13, and week 26) for PUMP.
Data were analyzed using both per-protocol (C85 %
compliance) and intention-to-treat (ITT). As there were no
significant differences between the two analyses, results
presented are for the ITT data. Analyses were performed
using IBM SPSS (version 21). Statistical significance was
set at p \ 0.05.
Results
PUMP Attendance, Adverse Events, and Training
Fifty participants aged between 58 and 75 years (PUMP
n = 24, age = 66 ± 4.4 years, CON n = 26, age = 66 ±
4.5 years) completed all baseline and follow-up testing
with four participants lost to follow-up from PUMP and
three lost to follow-up from CON (Fig. 1). Three of the
four participants lost to follow-up from PUMP were due to
fear of injury or injury associated with the intervention.
One participant (aged 64) withdrew due to intermittent
neck pain associated with shoulder press and chest press
and although lifting modifications were implemented the
participant was unable to continue the program beyond
8 weeks. A further participant (aged 60) reported an exacerbation of a previous knee complaint with squats and
lunges that did not improve following program modifications and ongoing physiotherapy treatment. A further participant (aged 63) withdrew after 4 weeks of training due to
fear of a neck or back injury associated with lifting. Mean
PUMP attendance was 48 (±12) classes over 26 weeks
V. P. Nicholson et al.: Bone density and low-load very high repetition resistance training
Fig. 1 Project flow chart
Assessed for eligibility (n=66)
Enrolment
Excluded (n= 9)
Not meeng criteria (n= 7)
Declined to parcipate (n= 2)
Completed Baseline tesng
(n= 57)
Allocated to intervenon (n=28)
Randomizaon &
Allocaon
Allocated to control (n=29)
Follow-Up
Lost to follow-up (n= 4)
Lost to follow-up (n= 3)
Family commitments (n=1), neck pain (n=1), knee pain (n=1),
fear of injury from intervenon (n=1)
Fractured scaphoid (n=1, cycling injury),
fractured rib (n=1), knee surgery (n=1)
Final Analysis
Analyzed (n= 24)
(range = 16–52 classes) resulting in an attendance compliance of 89 %. There was an increase in the amount of
weight lifted during PUMP (in terms of percentage 1RM)
for squats from week 1 to week 5 (p \ 0.001) and week 5
to 13 (p = 0.004). There was no significant difference in
the amount of weight lifted between weeks 13 and 26 for
squats (p = 0.76). Significant increases were only evident
for chest press from week 1 to 5 (p = 0.001). There were
no evident increases from week 5 to 13 (p = 0.15), or
week 13 to 26 (p = 0.25) (Table 2).
The Effect of PUMP on BMD
There were no group differences in any BMD measure at
baseline. There was a significant group-by-time interaction
for lumbar spine BMD (F (1, 49) = 8.58, p = 0.005)
(Table 4). Paired samples t tests demonstrated a nonsignificant increase for PUMP (t (23) = 1.61, p = 0.121)
and a significant reduction in BMD for CON (t (25) =
2.53, p = 0.018) in lumbar BMD. There was a significant
group-by-time interaction for total body BMD (F (1, 49) =
4.07, p = 0.049) with paired samples t tests showing a
significant reduction in BMD for PUMP (t (23) =
2.30, p = 0.031) and a non-significant change for CON
Analyzed (n= 26)
(t (25) = -0.67, p = 0.51). There were no group-by-time
interactions on femoral neck, total hip, or trochanter BMD.
The Effect of PUMP on Body Composition and Body
Weight
There were no baseline group differences in total body fat
mass or fat-free soft tissue mass. There were no significant
group-by-time interactions or time effects on total fat mass
or total fat-free soft tissue mass (Table 4). There was no
group-by-time interaction for body weight but there was a
significant time effect (F (1, 49) = 40.25, p \ 0.001) related to significant reductions from baseline to follow-up in
both PUMP (t (23) = 4.85, p \ 0.001) and CON (t (25) =
4.09, p \ 0.001).
The Effect of PUMP on Maximal Strength
There were no group differences in leg press or Smith
machine bench press at baseline. There were significant
group-by-time interactions for both leg press (F (1, 48) =
17.56, p \ 0.001) and Smith machine bench press
(F (1, 48) = 11.03, p = 0.002) (Table 4). Paired t tests
demonstrated a significant increase for PUMP in both leg
123
123
0.875 ± 0.113
0.937 ± 0.099
0.762 ± 0.089
Total hip BMD (g/cm2)
Trochanter BMD (g/cm2)
1RM leg press (kg)
41 ± 19
1.15 ± 0.25
770 ± 256
6435 ± 1468
30 ± 22
-13 ± 27
-17 ± 37
-13 ± 28
14 ± 17
12 ± 11
-2.4 ± 2.7
-2.11 ± 2.75
-1.70 ± 5.32
-0.57 ± 1.37
-0.52 ± 3.61
-0.21 ± 2.13
0.11 ± 2.78
1.01 ± 3.24
BMD bone mineral density, 1RM one-repetition maximum, METs metabolic equivalents
Values presented as mean ± SD
32 ± 21
1.32 ± 0.31
929 ± 249
Weekly METs
7419 ± 1729
Protein (g/kg body weight)
Calcium (mg)
25 ± 5
147 ± 31
22 ± 5
132 ± 28
Energy (kJ)
1RM Smith bench press (kg)
68.6 ± 10.0
36.71 ± 3.86
27.71 ± 8.75
1.053 ± 0.235
0.758 ± 0.088
0.935 ± 0.102
0.876 ± 0.118
1.099 ± 0.122
70.3 ± 9.5
37.50 ± 4.81
Total fat-free soft tissue mass (kg)
Body weight (kg)
1.059 ± 0.235
28.19 ± 9.40
Total body BMD (g/cm )
Total fat mass (kg)
2
1.088 ± 0.121
Femoral neck BMD (g/cm2)
36 ± 24
1.48 ± 0.62
854 ± 349
7710 ± 2474
23 ± 4
123 ± 25
64.4 ± 9.8
36.07 ± 3.36
24.21 ± 7.83
1.087 ± 0.095
0.747 ± 0.107
0.937 ± 0.099
0.857 ± 0.108
1.098 ± 0.136
Baseline
Mean percentage
change
Baseline
Follow-up
Control (N = 26)
Pump (N = 24)
Lumbar BMD (g/cm2)
Outcome measure
37 ± 25
1.28 ± 0.51
800 ± 390
6904 ± 1321
23 ± 4
122 ± 25
63.1 ± 9.5
36.17 ± 3.02
23.79 ± 7.66
1.089 ± 0.096
0.746 ± 0.119
0.909 ± 0.124
0.848 ± 0.136
1.075 ± 0.143
Follow-up
3±9%
-14 ± 36
-6 ± 39
-10 ± 29
0.0 ± 11
-0.81 ± 12
-2.1 ± 2.3
0.28 ± 2.62
-1.73 ± 5.65
0.18 ± 1.24
-0.13 ± 2.08
-2.99 ± 4.12
-1.05 ± 1.80
-2.09 ± 4.15
Mean percentage
change
Table 4 Pre- and post-intervention values for BMD, body composition, maximal strength, dietary intake, and weekly energy expenditure
0.268
0.761
0.027
0.892
0.548
0.096
0.000
0.009
0.002
0.187
\0.001
0.002
0.012
0.018
0.000
0.077
0.006
0.048
0.002
0.149
Partial g2 for
group-by-time
0.448
0.352
0.905
0.049
0.618
0.244
0.781
0.005
Group-by-time
interaction p
V. P. Nicholson et al.: Bone density and low-load very high repetition resistance training
V. P. Nicholson et al.: Bone density and low-load very high repetition resistance training
press (t (23) = 6.19, p \ 0.001) and bench press
(t (23) = 4.56, p \ 0.001).
Dietary Intake and Energy Expenditure
There were no differences between groups at baseline for
dietary intake or energy expenditure. There were no significant group-by-time interactions for any dietary intake
measure. There were however significant time effects for
total energy (F (1, 44) = 5.99, p = 0.019), protein (F (1,
44) = 6.48, p = 0.015), and calcium intake (F (1,
44) = 4.72, p = 0.036) that indicated a reduction in intake
for all three measures between baseline and follow-up for
both groups. There was a significant group-by-time interaction for energy expenditure (Table 4) due to a significant
increase in energy expenditure for PUMP (t (23) = 3.71,
p = 0.001) and a non-significant change for CON
(t (25) = 0.05, p = 0.64).
Discussion
We assessed the impact of a widely available pre-choreographed low-load very high-repetition resistance training
program (PUMP) on BMD and body composition in females aged over 55 years. There was a significant groupby-time interaction for lumbar spine BMD that was due to
a non-significant increase in the PUMP group and a significant reduction in the CON group. There were neither
any significant interactions for femoral neck, total hip, or
trochanter BMD, nor were there were any changes for fat
mass or fat-free soft tissue mass following training. Total
body BMD reduced for PUMP following training while
maximal strength as determined by 1RM assessment increased significantly following PUMP.
It was hypothesized that BMD would be maintained in
the PUMP group following 6 months of low-load very
high-repetition training. This hypothesis was only partially
supported by the significant reduction in lumbar spine
BMD in the control group and the small non-significant
improvement in PUMP. It should be noted that the small
improvement of 0.01 g/cm2 observed for PUMP is less
than the smallest detectable difference for the lumbar spine
[20]. Other low-load protocols have also typically failed to
demonstrate substantial positive changes in lumbar spine
BMD in similar aged cohorts [4, 8, 21]. To our knowledge,
only one study has reported positive changes in lumbar
spine BMD following a low-load resistance training program [5]. In that study, participants aged 55–74 years
trained for 40 weeks at either 40 % (3 9 16 reps) or 80 %
(3 9 8 reps) 1RM and all groups achieved similar gains in
lumbar spine BMD although gains tended to be higher for
men than women. It should be noted that the majority of
women in that study [5] were on HRT, and although a
subgroup analysis was performed to compare HRT and
non-HRT participants there was no control group for direct
comparison. There were no evident training effects at any
hip site in this study which is in contrast to many previous
resistance training studies in post-menopausal women [6,
7] that have typically identified a maintenance or improvement in BMD at least at one hip site compared to
controls. The results of previous low-load resistance
training are disparate as one study reported no improvement in BMD at the hip after 6 months of training [8] while
another reported improvements at the total hip and trochanter but no change at the femoral neck [5]. The conflicting results of these two studies are likely related to the
large difference in training volume as participants completed just one set of 13 repetitions at 50 % 1RM [8]
compared to three sets of 16 repetitions at 40 % 1RM [5].
The lack of improvement or maintenance in BMD observed at the hip and total body in this study are likely due
to a number of factors including high baseline BMD levels,
the lack of progressive overload in the program, the exercises used in the program, and low calcium intake of participants. The hip BMD values in this cohort at baseline
were generally higher than age-matched reference values
[22] which suggest that the current training protocol was
not enough to generate further improvement in those with
normal BMD. There was also minimal progression in the
weight lifted during the PUMP intervention, particularly in
the second half of the program. The lack of progression
was largely due to reported apprehension and fear of injury
associated with lifting heavier weights. This overall lack of
progression would have reduced the potential for osteogenic outcomes as strain thresholds would not have
been repeatedly exceeded [23]. A number of other studies
that have reported improvements in BMD at the hip have
included exercises such as hip abduction and hip flexion
that load the hip from various angles [5, 7] and produce
strong muscular contractions of the gluteus medius and
psoas major, respectively, which attach directly to the hip.
In contrast, this intervention was a generic whole-body
program that did not specifically target the hip. The exercises used in this study that load the hip (namely squats and
lunges) would have provided a mostly compressive load
and produced strong contractions of the gluteus maximus
[24] which does not attach directly onto the hip. Although
compressive loading provided by the squat [25], and forward leaning exercises such as deadlifts and dead rows
appeared to be beneficial for lumbar spine BMD in this
study, the lack of variation in loading torques may have
limited the osteogenic effect at the hip. The relatively low
levels of calcium intake in this cohort may have also influenced BMD. Although caution is warranted when determining calcium intake from 3-day food records, the
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V. P. Nicholson et al.: Bone density and low-load very high repetition resistance training
mean calcium intake was below 1000 mg for the majority
of participants and it is recommended that adults over
51 years intake 1000–1200 mg of calcium per day [26] as
the benefits of calcium supplementation on BMD are well
established. Furthermore, a significant reduction in calcium
intake occurred between baseline and follow-up which
could have limited positive changes in BMD.
Our hypothesis that fat-free soft tissue mass would increase in the PUMP group was not supported by the results
herein. It appears that training with loads less than 30 %
1RM twice per week does not promote improvements in
fat-free mass. The overall training volume may have been
too low [27] to promote changes and although hypertrophic
changes have been seen following low-load resistance
training [9, 28], to our knowledge there have been no reports of improvements in total body fat-free mass in older
adults following low-load training. Dietary factors may
have also limited potential changes in body composition.
For example, the distribution, quality [29], and individual
dose [30] of protein consumed throughout the day can influence muscle protein synthesis in older adults but was not
monitored. The reduction in total energy consumption may
have limited the ability to accrue fat-free soft tissue mass
[31] during resistance training. Although there were no
evident reductions in fat mass, both groups had significant
reductions in body weight over the course of the program.
Although caution is warranted when determining total energy intake from food records as under-reporting is common [32], the weight loss is largely attributed to the
reduction in energy intake in both the groups and the significant increase in activity among PUMP participants.
One-repetition maximum strength increased in the
PUMP group for both leg press and Smith machine bench
press. There was a 12 % improvement for leg press and
14 % for bench press. These gains are modest, particularly
for leg press when compared to previous low-load resistance training programs of similar durations [9, 33]. The
modest gains are largely due to the lack of load progression
over the course of the program and potentially due to
participants not training to voluntary muscle failure which
is imperative when training with light loads [34].
In this study the amount of weights lifted for squats and
chest press was monitored to determine changes in selfselected loads and to ascertain whether progressive loading
occurred. BodyPumpTM classes utilize a low-load very
high-repetition principle but exercises are not strictly performed to fatigue or momentary muscular failure which
may limit strength gains [28] and relative strain on bones
[35]. The progression of load was monitored by the class
instructors but each individual self-selected their weights
during the program. As demonstrated by the limited increases in squat and chest press load in the latter part of the
program it is clear that progressive overload did not occur
123
throughout the intervention. As shown in Table 2, participants trained above 20 % of 1RM for chest press during
the majority of the program while squats were performed at
approximately 10 % of predicted 1RM throughout. Recent
research demonstrated that older adults were able to train at
approximately 20 % 1RM for 80–100 repetitions when
using leg press and leg extension [9]. The results of this
study suggest that similar repetition ranges at equivalent
training loads are achievable for chest press but perhaps
due to the relative complexity of the task, it is likely that
more modest training loads are required to enable completion of very high repetitions with squatting.
The potential benefits of any exercise program need to
be considered in association with the potential risk of injury for that program. Three participants (10 %) withdrew
from training due to injury or fear of injury associated with
the program. This rate of training-related injury (or fear of
injury) is higher than other high-repetition resistance
training programs [9] and high-load training programs [36,
37] of similar durations. The comparably higher rate of
training-related issues may be associated with the more
complex lifting patterns during BodyPumpTM compared to
other training studies that have utilized machine weights.
Another potential issue is the limited direct supervision
achieved with one instructor.
A number of study limitations require attention. Firstly,
the participants in this study were healthy, moderately
active women without osteoporosis so the effect of such
training on sedentary adults or those with low bone density
cannot be determined. Calcium intake was monitored by
food records and although both groups reported similar
levels of calcium intake, no supplementation was provided
to ensure the attainment of recommended levels of calcium. The relatively small study size is likely to have affected the ability to detect small changes between groups
should they exist. The study duration of 6 months is a
further limitation as a bone remodeling cycle can take up to
9 months to complete. The program utilized herein was a
general whole-body low-load resistance training program
and as such did not specifically target the lumbar spine or
hip which will have limited the likelihood of providing
specific loading at these sites. Finally, the loads lifted
during the BodyPumpTM intervention were not progressively increased which would have limited the osteogenic
and hypertrophic effects of such training.
In conclusion, this study provides the first evidence that
low-load resistance training performed with a very high
number of repetitions can limit reductions in lumbar spine
BMD in active post-menopausal women. This form of
training does not have evident impacts on hip BMD or fat
mass and fat-free soft tissue mass. Although other established forms of resistance training may provide greater
BMD and body composition benefits to untrained
V. P. Nicholson et al.: Bone density and low-load very high repetition resistance training
middle-aged and older women, these findings suggest that
resistance training of very low loads can limit BMD declines if the training volume is adequate. Undertaking lowload high-repetition resistance training in this manner may
be more attractive to older adults who are fearful of
training with heavy loads or those that prefer a group
training environment. However, due to the relatively
complex lifting movements involved with BodyPumpTM
and the reported pain/injuries associated with training it is
unlikely to be suitable for a number of individuals. Further
work should assess the effectiveness of such training over a
longer period of time with a greater emphasis on individualized progressive overload and more specific loading
of the hip and lumbar spine.
11.
12.
13.
14.
15.
16.
17.
Acknowledgments This research was supported by PhD funding
provided by The Australian Fitness Network.
Conflict of interest Vaughan Nicholson, Mark McKean, Gary
Slater, Ava Kerr, and Brendan Burkett declare that they have no
conflict of interest.
Human and Animal rights and Informed Consent All participants
provided informed consent and all procedures performed were in accordance with the ethical standards of the the Human Research Ethics committee of the University and with the Declaration of Helsinki.
18.
19.
20.
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