The 30-second article
• After our third or fourth decade, we
experience reductions in bone mineral
density: this is typically accelerated in
women after menopause
• Resistance training can maintain and
improve bone mineral density in
post-menopausal women
• The researchers used BODYPUMP™
classes to assess the effect of
low-load very high-repetition
resistance training on bone mineral
density in older women
• DXA scans were used to assess the
bone mineral density of the lumbar
spine and hip prior to and after the
six-month study
• Low-load high-repetition resistance
training was found to go some way to
limiting reductions in lumbar spine
bone mineral density.
energy used for exercise/planned physical
activity during the program for both groups.
Results:
Mean
BODYPUMPTM
attendance was 48 (± 12) classes over 26
weeks (range = 16-52 classes) resulting in
an attendance compliance of 89 per cent.
There was an increase in the amount of
weight lifted during BODYPUMPTM (in terms
of percentage 1RM) for squats from week
one to week five. There was no significant
difference in the amount of weight lifted
between week 13 and 26 for squats.
Significant increases were only evident for
chest press from week one to five. There
were no evident increases from week five to
13 or week 13 to 26.
Discussion: It was hypothesised that
BMD would be maintained in the PUMP
group following six 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 0.01g/cm2
observed for BODYPUMPTM is less than
the smallest detectable difference for the
lumbar spine. Other low-load protocols
have also typically failed to demonstrate
substantial positive changes in lumbar
spine BMD in similar-aged cohorts. To our
knowledge, only one study has reported
positive changes in lumbar spine BMD
following a low-load resistance training
program. In that study, participants aged
55-74 years trained for 40 weeks at either
40 per cent (3x16 reps) or 80 per cent (3x8
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 were on hormone replacement
therapy (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. The results
of previous low-load resistance training
are disparate, as one study reported no
improvement in BMD at the hip after six
months of training, while another reported
improvements at the total hip and trochanter
but no change at the femoral neck. 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 per
cent 1RM compared to three sets of 16
repetitions at 40 per cent 1RM. 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 activity levels of the control group,
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 which suggests 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
BODYPUMPTM 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.
The relatively low levels of calcium intake
in this cohort may have also influenced
BMD. Although caution is warranted when
determining calcium intake from three-day
food records, the mean calcium intake was
below 1000mg for the majority of participants
and it is recommended that adults over 51
years intake 1000-1200mg of calcium per
day. 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 BODYPUMPTM
group was not supported by the results. It
appears that training with loads less than
30 per cent 1RM twice per week does not
promote improvements in fat-free mass.
The overall training volume may have been
too low to promote changes and although
hypertrophic changes have been seen
following low load resistance training, to our
knowledge there have been no reports of
improvements in total body fat-free mass in
older adults following low load training.
1RM max strength increased in the
PUMP group for both leg-press and Smith
machine bench press. There was an 11
per cent improvement for leg press and
14 per cent for bench press. These gains
are modest, particularly for leg press when
compared to previous low-load resistance
training programs of similar durations.
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.
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. These
findings suggest that resistance training of
varying loads can limit bone mineral density
declines if the training volume is adequate
in untrained middle-aged and older women.
Undertaking
low-load
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 individualised progressive
overload and more specific loading of the
hip and lumbar spine.
Acknowledgements
This research was supported by PhD funding
provided by Australian Fitness Network.
Fitness Research is a partnership between
Australian Fitness Network, the University
of the Sunshine Coast and the Australian
Institute of Fitness. Its mission is to
improve the health of Australians through
an improved body of fitness knowledge.
Access current and back issues of the Journal of Fitness
Research at fitnessresearch.com.au/journal
NETWORK WINTER 2015 | 65