The ageing process is associated with sarcopema: a reduction in muscle mass,
strength and power. Sarcopenia is responsible for diminished physical performance; it
affects the ability to perform activities of daily living and can severely impact quality
of life in older age. There is potentially no age group that can benefit more from
interventions to combat reduced muscle strength and power than an older population.
Whole body vibration (WBV) is a relatively new exercise intervention. WBV is
suggested to improve strength and power by stimulating the neuromuscular system
and inducing reflex muscle contractions. The potential for WBV to be used as a
strength training intervention for an older population was the rationale behind this
Study one was an investigation of the effects of eight weeks WBV on a range of
physical perfonnance measures in a healthy, older population. Forty three, older
adults (73.5 ± 4.5 yr, 168.2 ± 10.5 cm, 74.5 ± 11.1 kg) were divided into three groups:
15 to a WBV group (VIB), 13 to an exercise without vibration group (EX) and 15 into
a control group (CONT). The VIB and EX group interventions consisted of three
sessions per week for eight weeks. Outcome measures included isokinetic flexor and
extensor strength of the hip, knee and ankle, one-legged postural steadiness (OLPS),
sit-to-stand performance (STS), fast walk time and stair mobility.
Following the eight week intervention, the VIB group significantly improved OLPS
compared to the EX and CONT groups (p<0.05). The improvements in OLPS were
significantly affected by baseline values, with the largest changes evident for VIB
participants with a poorer initial score (p<0.01). WBV exercise can improve OLPS in
a healthy, older population. As improvements in OLPS were related to baseline
values, WBV as an intervention would appear to serve the most benefit for those that
exhibit diminished postural control.
The VIB group significantly improved ankle plantar flexor strength compared to the
EX and CONT group (18.2%, 5.0%, 0.9%) (p<0.05). The VIB and EX groups both
significantly improved knee extension strength compared to the CONT (8.1 %, 7.2%, -
2.0%) (p<0.05). There were no effects for hip flexor or extensor strength. The VIB
and EX groups both showed improved STS (12.4%, 10.2%) and Sm fast walk (3.0%,
3.7%) compared to the control (p<0.05). There were no effects for stair mobility
performance. While WBV exercise can be considered a plantar flexor strength
training intervention, it appears to have a disproportional effect on lower limb
strength. WB V did not facilitate knee extensor strength or physical performance
measures to a greater degree than the same exercise program without vibration. The
comparable change in physical perfonnance measures between the VIB and EX
groups appears linked to similar gains in knee extensor strength. Further, these similar
knee extensor strength improvements appears linked to the same body weight squats
performed by both the VIB and EX groups.
To explore the disproportional change in lower limb strength found in study one,
study two was designed to investigate the neuromuscular activation of the ankle, knee
and hip flexors and extensors during WBV. Ten healthy, older male participants (70.4
± 4.9 yr, 176.9 ± 7.8 cm, 78.6 ± 12.0 kg) completed a number of static exercises with
and without WBV. Activation of the soleus, gastrocnemius, tibialis anterior, vastus
medialis, rectus femoris, biceps femoris, iliopsoas and gluteus maximus were
recorded unilaterally with electromyography (EMG). EMG amplitude was normalised
and analysed with respect to each individual's maximum isometric strength values.
The absolute increases in EMG with vibration, above the non-vibration condition,
were compared between muscle groups and exercise conditions. The increase in
neuromuscular activity with WBV was significantly larger in the soleus and
gastrocnemius than muscles higher up the leg (p<0.05). Furthermore, the increase in
gastrocnemius neuromuscular activity was greatest when participants maintained a
heel raise position. It appears that WBV should be prescribed as an exercise
intervention that intends to specifically train the triceps surae musculature.
The results of study one and two suggested WBV be considered a localised strength
training intervention for older individuals which predominately targeted the plantar
flexors. The aim of study three was to examine the efficacy of WBV for a frail,
elderly population; to validate plantar flexor strength improvement with WBV and
examine the neuromuscular mechanisms associated with this adaptation. Seventeen
frail, older participants (88.2 ± 3.6 yr, 166.8 ± 8.2 cm, 71.7 ± 11.4 kg) were divided
into two groups: ten to a WBV group (VIB) and seven to a control group (CONT).
The VIB group undertook WBV three times per week for four weeks. Outcome
measures included isometric and isokinetic plantar flexor strength, single leg balance
performance and EMG of the gastrocnemius. The EMG signal was analysed for
amplitude and median power frequency. EMG amplitude was normalised with respect
to each individual's maximum isometric strength values.
WBV had no effects on single leg balance performance in a frail , older population.
This result is in contrast to study one that found significant improvements in OLPS in
a population of healthy, older adults. In contrast to study one participants, the frail
older adults in study three were unable to exercise on the WBV platform without
firmly grasping the handlebars for support. The difficulty maintaining balance whilst
undertaking WBV exercise is suggested to be a mediating factor behind the
improvements in balance observed in study one but not three.
Following the WBV intervention, the VIB group significantly improved isometric
(40.5%) and isokinetic (32.4%) plantar flexor strength compared to the CONT group
(1.5%, 2.9% respectively) group (p<0.05). The WBV group displayed a significant
32.3% increase and a 8.3% decrease in right medial gastrocnemius EMG peak
amplitude and EMG median power frequency respectively during isometric plantar
flexion (p<0.05). WBV can be considered an effective training intervention to
improve plantar flexor strength in frail, older adults. It is speculated that increased
plantar flexor strength with WBV exercise be explained at least in part by an
improvement in motor unit synchronisation and efficiency.