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Effects of 24 Weeks of Whole Body Vibration Training on Body Composition and Muscle Strength in Untrained Females
International Journal of Sports Medicine 2004; 1-5 DOI: 10.1055/s-2003-45238
M. Roelants1, C. Delecluse1, M. Goris1, S. Verschueren2
1 Exercise Physiology and Biomechanics Laboratory, Faculty of
Physical Education and Physiotherapy, Department of Kinesiology, Katholieke
Universiteit Leuven, Leuven, Belgium
2 Laboratory of Motor Control, Faculty of Physical Education and
Physiotherapy, Department of Kinesiology, Katholieke Universiteit Leuven, Leuven,
Belgium
ABSTRACT
.
The aim of this study was to investigate and to compare the effect of 24 weeks “whole body vibration” training and fitness training on body composition and on muscle strength. Forty-eight untrained females (21.3 ± 2.0 yr) participated in the study. The whole body vibration group (N = 18) performed unloaded static and dynamic exercises on a vibration platform (35 - 40 Hz, 2.5 - 5.0 mm; Power Plate®). The fitness group (N = 18) followed a standard cardiovascular (15 - 40 min) and resistance training program including dynamic leg press and leg extension exercises (20 - 8 RM).
Both groups trained 3 times weekly. The control group (N = 12) did not participate in any training. Body composition was determined by means of underwater weighing. Additionally 12 skin folds were assessed. Isometric (0°/s) and isokinetic (50°/s, 100°/s, 150°/s) knee-extensor strength was measured by means of a motor-driven dynamometer (Technogym®). Over 24 weeks there were no significant changes (p > 0.05) in weight, in percentage body fat, nor in skin fold thickness in any of the groups. Fat free mass increased significantly in the whole body vibration group (+ 2.2 %) only. A significant strength gain was recorded in the whole body vibration group (24.4 ± 5.1 %; 5.9 ± 2.1 %; 8.3 ± 4.4 %; 7.6 ± 1.5 %) and in the fitness group (16.5 ± 1.7 %; 12.0 ± 2.7 %; 10.4 ± 2.3 %; 10.2 ± 1.9 %), at 0°/s, 50°/s, 100°/s and 150°/s respectively.
In conclusion, 24 weeks whole body vibration training did not reduce weight, total body fat or subcutaneous fat in previously untrained females. However, whole body vibration training induces a gain in knee-extensor strength combined with a small increase in fat free mass. The gain in strength is comparable to the strength increase following a standard fitness training program consisting of cardiovascular and resistance training.
XXX
New trends in training science:
The use of vibrations for enhancing performance
by Carmelo Bosco, Marco Cardinale, Olga Tsarpela and Elio Locatelli
Introduction
The adaptive responses of the human body to
training stimuli have been investigated in depth over the past few years. Thanks
to the research carried out in different parts of the world, we know that the
adaptation to the training stimulus is related to the modification induced by
the repetition of daily exercises, which are specific to the movements executed
(Edington and Edgerton, 1976). These adaptations are related to the fact that
human skeletal muscle is a specialised tissue, which modifies its overall
functional capacity in response to regular exercise with high loads (McDonagh
and Davies, 1984).
The above-mentioned findings all
suggest that resistance exercise can be an effective means of enhancing muscular
performance. In this context it should be noted that changes within the muscle
itself constitute the most important adaptation to resistance exercise (Sale,
1988; Behm, 1995).
In fact, strength training responses
have been shown to be mediated by both neurogenic and myogenic factors (Moritani
and De Vries, 1979). Neural adaptations have been shown to be the first changes
to occur in the muscle, permitting gains in muscle strength and power in the
early stages of a resistance exercise programme in the absence of an increase in
the cross-sectional area of the muscle (Behm, 1995; Costill et al. 1979). It has
also been demonstrated that specific adaptations occur depending on the training
programme implemented (Sale and McDougall, 1981).
Strength
training can therefore be considered as a training stimulus, which produces
specific adaptations in human skeletal muscles, based upon the protocol,
utilised for training. The specificity of training effect from strength work has
been underlined by many authors (Sale, 1988; Behm, 1995; Morrisey et al. 1995;
Bandy et al. 1990) and the velocity specific effect has been highlighted as the
most interesting outcome of resistance exercise programmes. However, even if the
mechanisms underlining this velocity specific effect have not been clearly
defined, most importance has been given to the neural adaptations such as
improved co- ordination, increased activation of the prime mover muscles
(Moritani and De Vries, 1979), recruitment and
synchronisation.
The aim of most resistance training
programmes for elite athletes is to improve the mechanical power output for a
given movement, or to enhance speed. In thinking about a boxing punch, a
handball throw, a volleyball spike, or a shot putt, these movements involve the
exact timing of many muscle groups and are characterised by many coordinative
factors. However, boxers, handball and volleyball players and shot putters
undergo strength training sessions with the aim of improving their level of
performance. Any ideas injected into the deve1opment of a training plan for such
sporting disciplines must therefore be related to the specificity of each of the
movement patterns involved.
An optimal training plan
should be developed with some general exercises to improve muscle strength and
some specific exercises to improve muscle power and speed. The mechanical basis
of strength training is thus very simple: overload the biological system in
order to determine specific adaptations. Since the environment of our biological
sys- tem is characterised by the fact that we are all subject to the action of
gravity which pro- vides the major portion of the mechanical stimulus
responsible for muscle structure in everyday life and training, we need to alter
the biological system by increasing the gravitational load in order to enhance
strength. It should be remembered that specific programmes for strength and
explosive power training employ exercises performed with fast, abrupt variations
of gravitational acceleration (Bosco, 1992).
To give an example, the simulation of hypergravity (wearing vests with extra Ioads) has been utilised for improving explosive muscle power (Bosco et al. 1984; Bosco 1985). The overload or simulation of hyper- gravity are not the only means for changing the gravitational conditions. In fact, mechanical vibrations applied to the body can produce changes in the gravitational conditions and determine specific responses. The studies conducted from our group were aimed to investigate the effects of vibrations applied to the whole body or to part of it in terms of hormonal responses, explosive power, neuromuscular performance and strength. This article aims to present the latest findings on vibrations and some considerations for their use in the athletic setting.
The effects of vibrations on human
performance
The first study carried out by our group was
conducted to study the effects of whole body vibrations on the mechanical power
of the lower limbs. For this aim, fourteen active subjects involved in team
sports training voluntarily participated in the experiment. After being randomly
assigned to either an experimental or a control group, they were tested on an
Ergojump (MAGICA, Rome, Italy) for assessing vertical jumping ability. The
treatment group underwent whole body vibrations at a frequency of 26 Hz
(displacement = 10mm, acceleration = 54 mos-1 ) for 5 repetitions lasting 90
sec. each and separated by an interval of 40 sec.. This procedure was continued
for 10 days, the duration of vibration series being extended by 5 sec. every
consecutive day up to a total of 2 min. per set.
At the
end of the 10-day period the subjects were re-tested. The results showed
remarkable and significant (p<.05) enhancement of the height and mechanical
power of the best jump during the 5 sec. continuous jumping test (5sCJ)
(Bosco-Vittori test, see Bosco, 1992b). The average height of rise of the centre
of gravity in the 5sCJ was also significantly improved (p<.01). As expected,
no changes were observed in the control group (see Figures 1 and 2).
Considering the fact that the 5sCJ test is a
testing protocol characterised by a stretch-shortening cycle (SSC), a small
angular displacement and fast stretching speed, it can be considered that since
leg extensors muscles experience fast stretching this may elicit a concurrent
gamma-dynamic fusimotor input that would enhance primary afferent discharge.
Taking this into account, it was argued that the biological mechanism pro- duced
by vibrations was similar to the effect produced by explosive power training
(Bosco etal.1998).
After the latter experiment, another
study was conducted to observe the behaviour of human skeletal muscle following
one session of 10 minutes application of whole body vibration treatment. In this
case the subjects were six female elite volleyball players. They were tested
before and after the treatment while performing a maximal dynamic leg press
exercise with increasing loads (70, 90, 110 and 130 kg respectively) with a
sensor machine (Muscle Lab. Ergotest, Langesund Norway) able to calculate
average velocity, average power and average force corresponding to load
displacements (for details see Bosco et al. 1995).
After
the control test, one leg was randomly assigned to the experimental treatment
consisting of vibrations and the other was considered as a
control.
Results showed an alteration of the V-F and
P-F relationships after VT lasting only 10 min (see Figure 3; Bosco et al.
1999a). In fact, both relationships were shifted to the right indicating a clear
enhancement of performance which was previously observed only after several
weeks of resistance training (i.e. Coyle et al. 1981; Hakkinen and Komi,
1985).
The above mentioned findings are all related to the effectiveness of vibrations in enhancing performance in the lower limb muscles.
Vibrations applied to the upper limbs have
also been found to produce an enhancement of neuromuscular performance. In fact,
in a study conducted on 12 national level boxers, vibrations applied to the arm
determined an increase in average mechanical power (See Figure 4) during a
maximal arm curl with an extra load of 5% body mass. In this study, in which the
treatment consisted of five repe- titions of vibrations lasting 1 min. each with
1 min. rest interval at a frequency of 30 Hz, EMGrms was collected during the
arm curl test and during the treatments. The results showed a significant
decrease in the EMGjPower ratio following the treatment, suggesting an
improvement in the neural efficiency of the neuromuscular system (see Figure 5).
Moreover, the EMGrms recorded during each set of the vibration treatment reached
values higher than 200% of the baseline values.
The hormonal responses to vibrations were
studied in handball players who underwent 7 repetitions of 1 min. each of
vibrations and a test on vertical jumping performance. In this study, six
players of the Italian national team were tested before and after the whole body
vibration treatment of 7 min. on aspects such as blood concentration of
Testosterone (1), Cortisol (C), growth hormone (GH) and vertical jump
performances. The results showed significant decreases in vertical jumping
ability and T and C. suggesting that the 7 min. of treatment represented a
stressful load leading to an acute under-performance response (Bosco et al.
1999b). These results were similar to the response gained by a single session of
heavy resistance exercises. In this context it should be noted that some authors
have shown an increase in serum T (i.e. Weiss et al. 1983) after heavy strength
training exercises, while others have demonstrated relative strength loss and
hormonal decrease during one acute session of exercises (i.e. Hakkinen and
Pakarinen, 1985; Bosco et al., in-press).
For further
clarification of the hormonal response, another study was carried out with the
aim of evaluating a different protocol of administration of the vibration
treatment. In this study, fourteen male subjects were ex- posed to whole body
vibrations of 10 repetitions of 60 sec. with 60 sec. rest between each vibration
(after 5 reps there was a rest interval of 6 min.). The measurements carried out
before and after the treatment were: vertical jumping ability, maximal dynamic
leg press with an extra Ioad of 1600/0 of the subjects' body mass, EMGrms from
vastus medialis and lateralis recorded during leg-press measurement and blood
samples for determining T, C, and GH concentration in the blood. The results
showed an enhancement t>f jumping performance (+40/0, p<.001), a marked
and significant enhancement of mechanical power output when performing the leg
press, a reduction of EMG activity connected to an increase in neuro- muscular
efficiency through a decrease in EMG/P ratio. Significant increases in serum T
(+7%, p<.03) and GH (+4600/0, p<.014) were also found, together with a
significant reduction in C concentration.
All the
above-mentioned findings suggest that vibrations are without any doubt a useful
means for enhancing neuromuscular performance and triggering specific hormonal
responses. However, it is important to under- line that these responses are very
similar to the ones reported in the literature for strength training. It can
therefore be stressed that vibrations represent a valid alternative to strength
training or can be implemented in a strength training programme for further
improvement of human performance.
The scientific basis of vibrations
The facilitation of the excitability of the
spinal reflex has been elicited through vibration of the quadriceps muscle
(Burke et al., 1996). Lebedev and Peliakov ( 1991) have aIso suggested the
possibility that vibrations may elicit excitatory inflow through muscle spin
dle-motoneurons connections in the overall motoneuron inflow.
It has been demonstrated that vibration drives
alpha-motoneurons via the la loop producing force without decreasing motor drive
(Rothmuller and Cafarelli, 1995).
Although it has been
suggested that the vibration reflex, like the tendon jerk reflex, operates
predominantly or exclusively on alpha motoneurons and does not utilise the same
cortically originating efferent path- ways as are used when performing voluntary
contractions (Burke et al. 1976). it cannot be excluded that vibration
treatments can also affect voluntary movements. These suggestions are supported
by the present findings.
In fact the EMG recorded in the biceps brachii of the experimental group in the study conducted on boxers showed a significant enhancement (P<O.OOl) of the neural activity during the treatment period, as compared to normal conditions (Bosco et al. 1999a).
It has been shown that the vibration-induced
activation of muscle spindle receptors not only affects the muscle to which
vibration is applied, but also affects the neighbouring muscles (Kasai et al.
1992). A mechanical vibration (10-200 Hz), applied to the muscle belly or tendon
can elicit a reflex contraction (Hagbarth and Eklund, 1965). This response has
been named "tonic vibration reflex" (1VR). It is not known whether it can be
elicited by low vibration treatment (30 Hz), even if it has been suggested to
occur during whole body vibration at frequencies ranging from 1 to 30Hz (Seidel
, 1988).
The improvement of the muscle performance after a
short period of vibration training has been quoted (Bosco et al. 1998) to be
similar to what occurs after several weeks of heavy resistance training (e.g.
Coyle et al. 1981, Hakkinen and Komi 1985). In fact the improvement of the
muscle functions after resistance training has been attributed to the
enhancement of the neuromuscular behaviour caused by the increasing activity of
the higher motor centre (Milner -Brownet al., 1975). The improvement of muscle
performances induced by VT suggests that a neural adaptation has occurred in
response to the vibration treatments. In this context, the duration of the
stimulus seems to be both relevant and important. The adaptive response of human
skeletal muscle to simulated hypergravity conditions ( 1.1 g). applied for only
three weeks, caused a considerable improvement in the leg extensor muscle
behaviour (Bosco. 1985). Thus it is likely that both neural adaptation and the
length of the stimulus seem to play an important role in the improvement of
muscle performances (e.g. Bosco, 1985).
During the VT
utilised for the research conducted on the boxers, the elbow flexors were
stimulated for a total length of time of 300 seconds. The duration of the
treatment was similar to that required to perform an elbow flexion for 600
repetitions with a load similar to 50/0 of the subject's body mass. Such an
amount of repetitions would generally otherwise be distributed over 3 sessions a
week with 50 repetitions per time, taking one month to complete. The large
initial increases noted in muscle strength observed during the earlier weeks of
intense strength training can be explained through increases in maximal neural
activation (e.g. Moritani and De Vries , 1979).
To explain
how the increased neural output may occur is not as simple as how to explain the
intrinsic mechanism of neural adaptation. Furthermore, a net excitation of the
prime mover motoneurons could result from increased excitatory input, reduced
inhibitory input or both (e.g. Sale, 1988). After the VT period the EMG activity
was found to be rather lower or to be the same as com- pared to the
pre-treatment conditions even if, during the vibration, period an increment of
neural input to the muscle occurred. In this respect the decrease in the ratio
between EMG and mechanical power (EMG/P) demonstrated that VT induced an
improve- ment of the neuromuscular efficiency of the muscles involved in the
vibration treatment.
Vertical jumping ability has been
shown to increase following vibration treatment (Bosco et al. 1998; Bosco et al.
In-press). These improvements have been attributed to an enhancement of neural
activity in the leg extensor muscles, together with an enhancement of the
proprioceptors' feedback. During vibrations, the length of skeletal muscles
changes slightly. The facilitation of the excitability of spinal reflexes has
been shown to be elicited by vibrations applied to the quadriceps muscle (Burke
et al. 1996).
Once again, the influence of vibrations on
the neural drive of the la loop can playa crucial part in enhancing jumping
performance following vibration treatments. Even if the adaptive responses of
neuromuscular performance as measured by vertical jump tests cannot be fully
explained, it is important to consider that the effectiveness of the stimulus
can have both relevance and importance.
The adaptive
response of human skeletal muscle to simulated hypergravity conditions (1.1 g),
applied for only three weeks, caused a drastic enhancement of the neuromuscular
functions of the leg extensor muscles (Bosco. 1985).
The regular use of centrifugal force (2 g) for 3 months has initiated conversion of muscle fibre type (Martin and Romond, 1975). In the experiments conducted, the total length of the WBV application period was not very long (from 7 minutes to 100 minutes), but the disturbance to the gravitational field was quite consistent (5.4 g). An equivalent length and intensity of training stimulus (100 minutes) can only be reached by performing 200 drop jumps from 60 cm, twice a week for 12 months. In fact, the time spent for each drop jump is less than 200 ms, and the acceleration developed can barely reach 3.0 g (Bosco. 1992). This means stimulating the muscles for 2 min per week for a total amount in one year of 108 minutes. In a few words, vibrations can stimulate the biological system of athletes in the same way as strength training or explosive training and this stimulation can be applied in a much shorter period of time as compared to the time needed to perform traditional training sessions. It opens a new window in sports science and gives coaches and scientists new possibilities for studying and enhancing human performance.
Conclusion
The use of vibrations in an athletic setting
offers new possibilities to coaching science. Resistance training effectiveness
has been demonstrated due to the possibility of enhancing neuromuscular
performance, power output. strength and hormonal profile. However. the time
needed for these adaptations to occur is relatively long as compared to the
possibilities offered by vibration treatments. It should be recognised however,
that vibrations need to be viewed not as a substitute tool of resistance
exercise. but as a valid additional means to be implemented in a training
routine in association with all the other traditional methodologies nowadays
utilised. New studies need to be conducted to analyse chronic responses.
different treatment protocols and the effects of the association of vibrations
with conventional training means for improving the knowledge in this interesting
and exciting tool of sports science.
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