Die Effekte eines Power Plate-Trainings gegenüber einem Fitnesstraining auf die Muskelfitness und Muskelmasse bei untrainierten Personen. Y. Osawa ...
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Die Effekte eines Power Plate-Trainings gegenüber einem Fitnesstraining auf die Muskelfitness und Muskelmasse bei untrainierten Personen. Y. Osawa et al. Scand J Med Sci Sports, 2011: 1-12 Ziel der Studie: Untersuchung ob ein Power Plate-Training oder ein allgemeines konventionelles Krafttraining einen positiven Einfluss auf die Muskelfitness und den Muskelaufbau bei gesunden untrainierten Personen hat. Methoden: Diese 13- wöchige Studie wurde mit 32 gesunden untrainierten Probanden (Alter 22-49 Jahre) durchgeführt (85% der Teilnehmer waren Frauen). Die Teilnehmer wurden gleichmäßig in 2 Gruppen aufgeteilt: (1) Power Plate-Gruppe (35 Hz, low Amplitude); (2) Konventionelles Krafttraining (ohne Vibration). Alle Teilnehmer trainierten je 2-mal pro Woche über einen Zeitraum von 13 Wochen. Es wurden folgende Komponenten untersucht: Muskelzuwachs (MRI), Muskelkraft, Sprungkraft (Counter-Movement-Jump) und Kraftausdauer. Ergebnisse Das Power Plate-Training resultierte in einem stärkeren Muskelzuwachs als das konventionelle Training. Nur die Power Plate-Gruppe könnte einen Muskelzuwachs im Rückenstrecker erzielen. Die Power Plate- Gruppe zeigte eine größere Zunahme der Muskelkraftparameter (+63.5% und +76.7%) im Vergleich zu dem konventionellen Training (+25.6% und +17.8%). Auch die Sprungkraft war nach dem Power Plate- Training (+15.0%) im Vergleich zum konventionellen Training (+11.3%) deutlich verbessert. Beide Trainingsgruppen zeigten weiterhin eine Verbesserung der Rumpfmuskulatur. Fazit: Diese wissenschaftliche Studie beweist, dass ein 13-wöchiges Power Plate-Training bei untrainierten Personen in einem Muskelzuwachs und einer deutlichen Verbesserung verschiedener Muskelkraftparameter resultiert. Ein Muskelzuwachs im Rückenstrecker könnte nur nach dem Power Plate-Training, nicht aber nach dem konventionellen Krafttraining beobachtet werden. Die beobachteten Kraftverbesserungen der Rumpfmuskulatur und die höhere Muskelmasse im Rückenstrecker deuten darauf hin, dass ein Power Plate-Training förderlich in der Prävention und Rehabilitation von chronischen Rückenschmerzen förderlich sein kann. © Power Plate Abstract Muskelfitness V 1.0, Stand 01.08.2012 Seite 1 von 1
Scand J Med Sci Sports 2011 & 2011 John Wiley & Sons A/S
doi: 10.1111/j.1600-0838.2011.01352.x
Effects of resistance training with whole-body vibration on muscle
fitness in untrained adults
Y. Osawa1, Y. Oguma1,2
1
Graduate School of Health Management, 2Sports Medicine Research Center, Keio University, Kanagawa, Japan
Corresponding author: Y. Osawa, 4-1-1, Hiyoshi, Kohoku-ward, Yokohama City, Kanagawa, Japan. Tel: 181-45-566-1090,
Fax: 181-45-566-1067, E-mail: yosawa1028@gmail.com
Accepted for publication 17 May 2011
The effects of resistance training (RT) combined with whole- muscle (vs the RT group) were observed in the RT-WBV
body vibration (WBV) on muscle fitness, particularly muscle group (110.7%, Po0.05; 18.7%, Po0.05) compared with
hypertrophy and neuromuscular performance, are not well the RT group (13.8%, P 5 0.045; 0.0%). Higher increases
understood. We investigated the effects of WBV in healthy, from baseline were also observed in maximal isometric
untrained participants after a 13-week RT course by force, concentric knee extension torque, countermove-
performing magnetic resonance imaging and by measuring ment-jump, and maximal isometric lumbar extension torque
maximal isometric (with electromyography) and isokinetic in RT-WBV (163.5%; 176.7%, 115.0%, and 151.5%,
knee extension strengths, isometric lumbar extension tor- respectively; Po0.05) than in those of RT (125.6%,
que, countermovement-jump, knee extension endurance, P 5 0.001; 117.8%, P 5 0.18; 111.3%, P 5 0.001; and
and sit-ups. Thirty-two individuals (22–49 years old) were 126.4%, Po0.001, respectively). The WBV-induced in-
randomly assigned to RT groups with (RT-WBV, n 5 16) or creases in muscle hypertrophy and isometric lumbar exten-
without WBV (RT, n 5 16). Following the RT course, sion torque suggest a potential benefit of incorporating
significantly higher increases in the cross-sectional areas WBV into slow-velocity RT programs involving exercises
of m. psoas major (vs baseline values) and erector spinae of long duration.
Recently, resistance training (RT) combined with ination of the effects of WBV training on muscle
whole-body vibration (WBV) has become popular hypertrophy is needed.
among untrained middle-aged people. Although it To date, a standard WBV training program has
has been suggested that RT with WBV enhances not been established. The degree of muscle stimu-
muscle strength, particularly in untrained adults lation during WBV exercise is dictated by the
(Marin & Rhea, 2010), the efficacy of WBV when amount of force generated by the vibration platform
incorporated into RT programs for improving mus- (actuator) that is transferred to the human body
cle mass, strength, power, and endurance compared (resonator) (Rittweger, 2010). It was demonstrated
with the identical training without WBV is less clear. previously that the acceleration of vibration plat-
Among six recent studies, only Delecluse et al. (2003) forms increases under weight-loaded conditions (Pel
found that WBV led to significant additional in- et al., 2009; Osawa et al., 2011b). If the actuator
creases in muscle strength and power, as the other produces a larger force, the degree of response in the
studies did not detect any additional effects resulting resonator would be expected to correspondingly
from the addition of WBV to RT programs (de increase. However, as a few studies did not detect
Ruiter et al., 2003; Ronnestad, 2004; Kvorning any additional muscle strength or power gains with
et al., 2006; Carson et al., 2010; von Stengel et al., heavy-loading RT regimens combined with WBV
2010). However, two studies reported that exercise [e.g., eight repetitions of 8–10 repetition maximum
combined with WBV significantly increased the (RM) or 10 repetitions of 75–90% 1 RM], conven-
cross-sectional area (CSA) of thigh muscles in older tional RT regimens do not appear suitable for WBV
individuals (460 years of age) (Bogaerts et al., 2007; training programs (Ronnestad, 2004; Kvorning et al.,
Machado et al., 2010). Although these represent the 2006; Carson et al., 2010). Therefore, longer expo-
only findings to suggest that WBV training stimu- sure to vibration during muscle contractions may be
lates morphological changes in muscles, an identical necessary to elicit WBV per se effects on neuromus-
exercise group in the absence of WBV was not cular systems. This speculation is supported by a
included in the evaluations. Therefore, further exam- study of Bongiovanni et al. (1990), who found that
1Osawa & Oguma
reductions of electromyographic activity, motor unit University and written informed consent was obtained from
firing rates, and contraction force were observed all participants.
after 30-s muscle contractions with locally applied
vibration. This may have been due to vibration-
Randomization procedure
induced pre-synaptic inhibition and/or transmitter
depletion in Ia excitatory pathways. In consideration Participants were randomly assigned to either an RT with
WBV (RT-WBV, n 5 17) group or a non-WBV RT (RT,
of these reports, we anticipated that an intentional n 5 16) group (Fig. 1). A restricted randomization (blocking
slow-velocity RT program that increases the time and stratification) was used to allocate participants into one of
muscles are under tension would be suitable to the two groups. First, six matrices (age, 20s, 30s, or 40s;
combine with WBV. In addition, slow-velocity RT gender, female or male) were created to stratify the partici-
also involves less momentum, resulting in a more pants. Second, we prepared six envelopes for each stratified
group, with each envelope containing 10 cards labeled with
evenly applied muscle force throughout the range of either ‘‘RT’’ or ‘‘RT-WBV’’ (RT-WBV:RT, 5:5). Finally, after
motion and is amenable to the addition of lighter the completion of all of the pre-training tests, each participant
external loads than conventional training regimens, drew a card from the envelope corresponding to their stratified
even when progressive overloading is needed to group, and was allocated to either training group as desig-
overcome strength-gain plateaus (Westcott et al., nated by the selected card.
2001; Tanimoto & Ishii, 2006). Here, we hypothe-
sized that slow-velocity RT combined with WBV Training programs
would lead to increases in muscle mass, strength,
power, endurance, and neuromuscular activities. Vibration conditions
The aim of this study was to investigate the effects To deliver WBV to the RT-WBV s
group, a synchronous
of 13-week RT combined with WBV on muscle vibration device (Power Plate Next Generation, Power Plate
hypertrophy, strength, power, neuromuscular activ- International, Northbrook, Illinois, USA) equipped with the
platform pad provided by the manufacturer was used. We
ity, and local muscle endurance compared with the applied WBV at a frequency and amplitude of 35 Hz and
identical training lacking WBV in untrained, healthy 2 mm, respectively, throughout the trial because nearly all
adults. Participants in both training groups were participants in a pilot study experienced discomfort in their
subjected to several performance tests, in addition head and chest regions when exercises were performed in
to measuring the CSA of abdominal muscles, to supine and prone positions at higher frequencies or amplitudes,
or without the platform pad. Mean acceleration magnitudes of
assess the effects of WBV on the basis of changes in the vibration platform device with and without weight loading
the pre-training and post-training measurements. were reported in a previous study (Osawa et al., 2011b).
RT program
Materials and methods
After performing a standardized warm-up involving operating
Subjects an ergometer for 5 min followed by stretching (e.g., modified
Figure 1 shows the flow of the study. Thirty-three untrained hurdler’s stretch), participants, who wore socks, but no shoes,
adults [6 males (M) and 27 females (F), 22–49 years old] performed two exercises for lower extremities with their hands
volunteered for this study. Participants were recruited from free (half squat, knee angle, 201–901 (full extension 5 01), hip
local residents (n 5 26) and from graduate school students of angle, 201–301, to 901 (full extension 5 01); Bulgarian squat,
Keio University (n 5 7) using posted advertisements. Power knee angle, 201–901; hip angle, 201–301 to 901) and six
analysis was performed with the power set at 0.80 and an a- exercises for trunk muscles (roll back, trunk curl, hip walking,
level of 0.05 under the hypothesis that RT with WBV would leg raise, back extension, and stabilization exercise) on the
increase the CSA of m. psoas major as the primary outcome. vibration platform either with (RT-WBV group) or without
The analysis setting with balanced data (equal number of WBV (RT group) (Table 1). The position adopted in each
participants in each group), and an expected effect size and exercise, including photographs, has been reported previously
standard deviation (SD) of 0.2% and 0.19%, respectively, (Osawa & Oguma, 2011a). Although there is no well-estab-
revealed that a sample size of 14 participants in each test group lished movement cadence for achieving optimal muscle fitness
was required for the detection of WBV effects. The eligibility gains, here, we configured the training program to consist of a
criteria for participants were 20–49 years old, no experience cadence of 4 s concentric phase (lifting), 2 s no-relaxing phase
with RT for at least 6 months before the study, could refrain (isometric phase), and 4 s eccentric phase (lowering) to mini-
from engaging in any regular vigorous activities, strength mize momentum and to achieve a more evenly applied muscle
training, or stabilization training, and could maintain routine force throughout the range of motion (Smith & Bruce-Low,
daily life throughout the trial. The health and medical history, 2004). Each exercise was performed for eight repetitions with
current medical conditions, and signs and risk factors of the cadence with intermittent rest periods of 60 s between sets,
cardiovascular or orthopedic diseases of each potential parti- with the exception of the roll back and hip walking exercises,
cipant were evaluated using a self-administered Physical which were performed continuously for 64 and 48 s, respec-
Activity Readiness Questionnaire (PARQ; Thomas et al., tively, without any isometric phase. All cadences were strictly
1992). If an individual answered ‘‘No’’ to all questions, he controlled using a metronome (SQ-77, Seiko, Tokyo, Japan).
or she was considered a suitable candidate and was entered Weight loading was based on individual bodys mass (Table 1).
into the study. The exclusion criteria were pregnancy, history As the g force produced by the Power Plate increased with
of severe orthopedic abnormality, diabetes, or acute hernia. weight loading on the platform, the g force experienced by
This study was approved by the local ethics committee of Keio participants in the RT-WBV group and/or weight loading
2Vibration training effects on muscle fitness
Fig. 1. The flow of participants through the trial. Participants were randomly assigned to one of the two training groups and
performed twice-weekly training (60-min sessions) either with (RT-WBV) or without (RT) WBV (frequency, 35 Hz; amplitude,
2 mm) for a 13-week training period. All participants were subjected to tests and assessments before, during (after a 7-week
training period), and following training (after a 13-week training period) to evaluate muscle hypertrophy, muscle performance
(muscle strength, power, endurance), physical activity, and nutritional assessments, with the exception of MRI tests and
physical activity assessment, which were only performed before and after the training period. FFQg, food frequency
questionnaire based on food groups, MRI, magnetic resonance imaging, RT, resistance training; RT-WBV, RT with whole-
body vibration.
Table 1. Exercise protocol used in the present study
Period Volume (set/ Weight-loading conditions
(week) exercise)
Leg exercises Trunk exercises
Squat (two legs) Roll back exercise Hip walking
Bulgarian squat Trunk curl Leg raise
(one leg) Back extension Stabilization
Pre-tests
1 1 Body weight Body weight Body
2–4 2 weight
5–7 2 10% and 15% body mass for women and for men, respectively
Mid-tests
8–13 2 Progressively increased every 2 weeks and reached 30% and Progressively increased
45% of body mass in women and men, respectively using 1–3.4
and 1–5. 6 kg dumbbells
in women and
men, respectively
Post-tests
A weight jacket (Kool Katz, Pokal Industries Pvt Ltd., Sialkot, Pakistan), in which 1–20 kg of weight bars could be added around the abdominal and lower
back area, and dumb bells were used for additional weight loading for the two leg exercises. Dumb bells were used for three of the trunk exercises.
intensity within the two groups would have varied if training of two participants, who were strictly and closely supervised
intensity was decided by the maximum strength test. Therefore, by the investigators. After each training session, participants
we configured the weight loading based on the performance of ingested a multi-vitamin supplement (Nature Made, Otsuka,
a few individuals (e.g., not overly challenging and the degree of Tokyo, Japan) to provide the minimum reference dietary
muscle soreness the day after training session) in pilot trials. s intakes recommended by the Japanese Ministry of Health
As the laboratory was equipped with two Power Plate and to minimize the effects of confounding related to insuffi-
machines, training sessions were conducted with a maximum cient food intake, particularly vitamins.
3Osawa & Oguma
Magnetic resonance imaging (MRI) the body center of gravity (h) during countermovement-jump
MRI was performed using a 1.5 T imager (Intera 1.5t, Phillips (h 5 1/8gt2, where g 5 9.81 m/s2). In a standing position,
Medical Systems, Best, the Netherlands). As it has been participants first made a downward movement by bending
suggested that soft tissues, joints, or items such as shoes and their knees and hips, and then jumped as high as possible while
pads dampen the vibration magnitude (Rittweger, 2010), we keeping their hands on their waist. After returning to a
anticipated that exercises performed in prone and supine standing position, the participants were permitted a short
postures would maximize the vibration efficacy on trunk intermittent rest of a few seconds between each jump. The
muscles, which would be in direct or close contact with the jump was repeated five times, and the mean value of counter-
platform, when compared with the effects of standing exercises movement-jump height (cm) was recorded. The test was
on thigh and leg muscles. Thus, we decided to configure the RT conducted twice, with an interval of 3 min, and the highest
exercise program to target mainly trunk muscles and investi- mean jump height was used for further analyses. The ICC for
gated the additional WBV effects on muscle hypertrophy using test–retest reliability of the countermovement-jump test was
MRI only in trunk muscles due to budget restraints. The CSA r 5 0.96.
of m. psoas major, m. rectus abdominis, m. anterolateral
abdominal (IABD; obliquus internus abdominis1obliquus ex- Maximal knee extension strength and endurance tests
ternus abdominis1transversus abdominis), multifidus, erector
spinae muscle, and quadratus lumborum muscle were deter- Maximal voluntary isometric force and isokinetic knee exten-
mined from lumbar axial MRI images, which were obtained sion torque, and local muscular endurance powersand work
parallel to the L4–L5 disc space level. A single 10 mm axial slice were measured on the right side using a Kin-Com KC500H
was obtained using a T1-weighted image. The other MRI device (Chatteex, Hixson, Tennessee, USA). During the tests,
parameters were as follows: TR, 450 ms; TE, 20 ms; FA, 901; the right upper leg, ankle, and the hips were stabilized with
NA, 1; matrix, 256 256; FOV, 400 400 mm; pixel size, safety belts. After gravity correction was performed in accor-
1.56; scan time, 11.3 s (SENSE mode); and TSE factor, 6. A dance with the manufacturer’s guidelines, participants were
body coil was used to image abdominal sections (SENSE-Body seated with a hip joint angle of 801 and arms crossed in front
Coil, Phillips Medical Systems). The DICOM images obtained of the chest, and maximal isometric 5-s contractions were then
were analyzed with ZedView 3.1 software (Lexi, Tokyo, Japan). measured at a knee angle of 601. Maximal isokinetic con-
Segmenting the CSA of muscle was based on the brightness of centric and eccentric knee extension torque was measured at
the MR value, and if a part of the CSA delineation was unclear, knee angles of 801–201 and a velocity of 601/s. The local
a free hand area calculation was performed (Arai et al., 2004). muscle endurance test, consisting of 30 consecutive concentric
The average of the CSA of each left and right muscle was used knee extensions, was performed at knee angles of 801–201 and
for further statistical analysis. a velocity of 601/s. Total work (J) and average power (W)
All MRI measurements were performed by a radiologist during local muscular endurance test were measured. The
(M.R.I.) and a medical software programmer (CSA measure- measurements for all strength tests were repeated twice with 3-
ments), who had no knowledge of the study design (e.g., min rest intervals, and the peak force or torque obtained,
purpose of the present study, participants’ information, and which was normalized to body mass (N/kg, or N m/kg) for the
grouping), except that the CSA measurements were supple- maximal voluntary isometric and isokinetic tests, respectively
mentarily performed by an investigator for five women’s data were used for further analyses. The ICC for test–retest
and all the CSA of multifidus, erector spinae muscle, and reliability were r 5 0.97 (isometric contraction), r 5 0.86 (iso-
quadratus lumborum muscle with free hand area calculation kinetic concentric contraction), r 5 0.91 (isokinetic eccentric
using the DICOM viewer software OsiriX ver. 3.9 (http:// contraction), and r 5 0.79 (local muscular endurance).
www.osirix-viewer.com). Intraclass correlation coefficient
(ICC) tests were also evaluated within one week of all of Surface electromyography (sEMG)
measurements for four participants and one investigator;
r 5 0.99 (m. psoas major), r 5 0.98 (m. rectus abdominis), sEMG signals from the vastus medialis (VM) and vastus
r 5 0.91 (IABD), r 5 0.94 (multifidus), r 5 0.97 (erector spinae lateralis (VL) muscles of the right leg were recorded using a
muscle), and r 5 0.96 (quadratus lumborum muscle). TeleMyo 2400 T V2 system (Noraxon Inc., Scottsdale, Ari-
zona, USA) with disposable Ag/AgCl snap electrodes (EM-
272, Noraxon Inc.) during the Bulgarian squat exercise with or
Performance tests without WBV and the isometric knee extension force test. The
figure eight-shaped adhesive area of the electrodes was
After the standardized warm-up described in the RT program 4 2.2 cm, the two circular conductive areas were 1 cm in
section, the following performance tests (listed in the order diameter, and the inter-electrode distance was 2 cm. After the
they were conducted) were evaluated before (Pre), after 7 skin over the respective muscle belly was lightly abraded, the
weeks of training (Mid), and after the completion of the 13- electrodes were fixed in accordance with the Surface Electro-
week training period (Post). Participants performed light myography for the Non-Invasive Assessment of Muscles
stretches between tests. guidelines (Hermens et al., 1999). After the electrodes were
attached, the participants sat on a chair for at least 5 min to
Countermovement-jump test for muscle power acclimatize the skin with the electrodes. The sEMG signals
were sampled at 3000 Hz and subsequently band-pass filtered
As the recruitment of participants was divided into two (15–500 Hz).
periods, and the instrument used for the muscle power test The processing of sEMG data was performed using MyoR-
was only available during the second recruitment period, only esearch XP software, Master Package ver. 1.06.74 (Noraxon
23 participants (RT-WBV, M: 1, F: 11; RT, M: 1, F: 10; Inc.). As suggested previously by Abercromby et al. (2007),
38.6 8.2 years old) performed
s
countermovement-jumps raw EMG signals obtained during exercise with WBV include
while wearing a Myotest accelerometer on the waist (Myot- motion artifacts caused by the WBV source. Thus, we applied
est, Royal
s
Oak, Michigan, USA) (Casartelli et al., 2010). The band stop filter analyses at Nfv, where fv is the vibration
Myotest automatically calculates jump height from the frequency, and the stop-band was equal to Nfv 0.5 Hz (i.e.,
obtained flight time (t) by estimating the height of the rise of 0.5fv, 1fv, 2fv, . . ., 14fv). The raw EMG signals obtained from
4Vibration training effects on muscle fitness
the isometric contraction test were converted to an average correction) were performed to evaluate the significance of time
root-mean square (EMGrms) with 0.5 s smoothing windows effects and differences between groups. A selective bivariate
to compare the RT-WBV and RT groups. The 0.5 s time relationship (between percent change in muscle force/torque,
epochs around the isometric contraction
s
force peak, which muscle CSA, and EMG amplitude) was investigated using
were identified using a Kin-Com KC500H device, were used Pearson’s correlation coefficient. PASW software version 18.0
for further analyses. for Macintosh (SPSS Inc., Tokyo, Japan) was used for all
statistical analyses. The level of significance was set at
Po0.05, and all values are presented as the mean SD.
Trunk muscle strength and endurance
We measured back extensor torque with an isometric lumbar
extension machine (MedX, Orlando, Florida, USA) using
testing positions that were standardized following the manu- Results
facturer’s guidelines. After the participant was seated in the Participant baseline characteristics
lumbar extension machine, the pelvis was stabilized, and while The characteristics of the participants are summar-
the participant rested against the upper back pad (the angle of
full extension was 01), a counterweight was adjusted to ized in Table 2. No significant differences between the
neutralize gravitational force on the head, torso, and upper RT-WBV and RT groups at baseline were observed
extremities. Maximal isometric lumbar extension torque was in any of the evaluated characteristics, except the
then measured in the sitting position through a 721 arc of CSA of erector spinae muscle. In addition, with the
lumbar motion (at 721, 601, 481, 361, 241, 121, and 01 of trunk exception of six individuals (RT-WBV, M: 2, F: 2;
flexion). The ICC for test–retest reliability of each angle
ranged from r 5 0.83 to 0.94. The maximal isometric lumbar RT, M: 1, F: 1) who had once engaged in regular RT
extension torque at 601 of trunk flexion was used for further as part of a college sports team, all participants were
analyses, because the position gave the highest reliability in novices for RT.
our laboratory (r 5 0.94) and in a previous report (r 5 0.96) One male in the RT-WBV group dropped out of
(Graves et al., 1990). the study after the mid-training tests due to conflicts
Abdominal muscle endurance was evaluated by the total
number of sit-ups performed in 30 s. We applied the sit-up test with his job; however, the other participants com-
used in the New Japan Fitness Test formulated by the pleted the 13-week training program and all of the
Japanese Ministry of Education, Culture, Sports, Science, evaluation tests (Fig. 1).
and Technology, which is nearly identical to that used in the
Eurofit Fitness Testing Battery, with the exception of arm
position. A detailed explanation of the testing procedure was
reported previously (Osawa et al., 2011b). The ICC for test– Muscle activity during exercise
retest reliability of the sit-up test was r 5 0.91. sEMG signals from the VM and VL muscles re-
corded during Bulgarian squat exercise illustrate the
differences in muscle activity for contractions per-
Physical activity and nutritional assessment during the trial
formed in the presence and in the absence of WBV
The food intake of participants was assessed by a food (Fig. 2). In the RT group, the EMG signals from VM
frequency questionnaire based on Food Groups (FFQg) soft-
ware version 2.0, which is an optional software of ‘‘Excel Eiyo- and VL showed 44.6 14.3% and 49.3 21.4%
kun’’ (Kenpaku-sha, Tokyo, Japan) that conforms to the Fifth maximal voluntary contraction (MVC), respectively,
Edition of Standard Tables of Food Composition in Japan during exercise, while the total duration that the
compiled by the resources research committee of the Science signals did not reach 40% MVC was 42 and 36 s,
and Technology Agency (Tokyo, Japan) (Takahashi et al., respectively, during the 80 s period that each exercise
2001). The FFQg was conducted before, after the seventh
week of training, and during the last training week. set was performed (Fig. 2a). In contrast, the EMG
Physical activity of each participant was assessed using a
uniaxial accelerometer (Lifecorder EX, Suzuken Co. Ltd., Table 2. Participant characteristics
Nagoya, Japan) for at least 1 week, including 5 weekdays
and 2 weekend days, once before the trial and again around Characteristic RT-WBV, n 5 16 RT, n 5 16
the time of the last training week. Mean total step counts per (F:14, M:2) (F:13, M:3)
day were used for further analyses.
Age (years) 36.8 8.4 37.7 9.5
Height (cm) 161.2 6.4 164 5.9
Body mass (kg) 55.3 8.8 58.8 9.0
Statistical analyses BMI (kg/m2) 21.1 2.3 21.8 2.3
Group differences in age, body mass, BMI, total physical Total physical activity 10 565 2022 9248 3772
activity, and the results of the FFQg at baseline were deter- (steps/day)*
mined by the unpaired t-test. Normality and equal variance Total energy intake (kcal/day) 1856 366 2080 470
assumptions were performed using the Kolmogorov–Smirnov Protein (%) 13.1 1.3 13.9 1.9
and Levene tests, respectively. If normality and equal variance Fat (%) 29.9 7.0 30.1 4.4
were assumed, longitudinal changes in all outcomes were Carbohydrate (%) 56.2 5.6 56.0 5.4
compared within the groups using two-way ANOVA (group
time) with repeated measurements; otherwise, the percentage *Total physical activity was determined by the number of step counts per
change from baseline values was tested using either the day, as measured using a uniaxial accelerometer.
unpaired t-test or one-way ANOVA. If an F-value was found BMI, body mass index; RT, resistance training group; RT-WBV, resistance
to be significant, preplanned contrast analyses (Bonferroni training with whole-body vibration group.
5Osawa & Oguma
Fig. 2. Typical surface electromyographic signals from the vastus medialis and vastus lateralis during Bulgarian squat exercise.
Signals were recorded during exercise combined without (a) or with (b) whole-body vibration (WBV), and an external load of
12 kg for female participants with 51 kg body mass. Signals were recorded from the first to last repetition of the eight-repetition
exercise.
Fig. 3. Representative axial magnetic resonance imaging (MRI) scans of the L4-5 disc space level at pre-training (a) and post-
training (b). Muscle hypertrophy in m. psoas major (10.7%, Po0.001) and erector spinae muscle (8.5%, P 5 0.001) occurred in
response to slow-velocity resistance training coupled with WBV. ES, erector spinae muscle; IABD, m. anterolateral abdominal
(obliquus internus abdominis1obliquus externus abdominis1transversus abdominis); MF, multifidus; PS, m. psoas major;
QL, quadratus lumborum muscle; RA, m. rectus abdominis.
signals, which were recorded with a band-stop filter, (110.7 5.3%, Po0.001) and RT groups (13.8
from VM and VL in the RT-WBV group showed 7.5%, P 5 0.045). A significantly higher percent
48.9 11.7% and 52.4 20.9% MVC, respectively, change increase in erector spinae muscle in the RT-
while the total duration that the signals did not reach WBV group was also detected compared with that of
40% MVC was 21 and 30 s, respectively, during the the RT group (P 5 0.04, unpaired t-test). In addition,
80 s period that each exercise set was performed. although no significant group time interactions
were found in the CSA of m. rectus abdominis
(P 5 0.85) or IABD (P 5 0.53), significant time ef-
CSA of abdominal muscles fects were observed in both these muscles (Po0.001
To assess the effect of WBV on muscle hypertrophy, and P 5 0.002, respectively). Finally, no significant
participants of both training groups were subjected group time interactions were detected in the CSA
to MRI testing before and after the 13-week training of quadratus lumborum (P 5 0.94) or multifidus
period (Fig. 3). From the MRI images of the abdom- muscles (P 5 0.86).
inal area, changes in the CSA of several target
muscles were determined and compared between
the two training groups. As shown in Fig. 4, a Countermovement-jump test
significant group time interaction was observed Changes in muscle power were evaluated using the
in the CSA of m. psoas major (P 5 0.03), countermovement-jump test, which revealed signifi-
which significantly increased in both the RT-WBV cant group time interactions in jump height
6Vibration training effects on muscle fitness
Fig. 4. Sizes of cross-sectional areas at the L4-5 disc space level determined from magnetic resonance imaging (MRI)
performed pre-training and post-training. All values are presented as the mean SD. Black bars represent the resistance
training with whole-body vibration group (RT-WBV), whereas white bars represent resistance-training group (RT). ES, erector
spinae muscle; IABD, m. anterolateral abdominal (obliquus internus abdominis1obliquus externus abdominis1transversus
abdominis); MF, multifidus; PS, m. psoas major; QL, quadratus lumborum muscle; RA, m. rectus abdominis. wSignificant
group time interaction (Po0.05, two-way repeated-measures ANOVA). *Significant difference (Po0.05, Bonferroni
correction). zSignificant time effect (Po0.05, two-way ANOVA). §Significant difference was observed between the groups
at baseline (unpaired t-test).
(Table 3). A comparison of the mean pre-treatment EMGrms during isometric extension in VM
and post-treatment values revealed that significant (P 5 0.012) (Fig. 5). In addition, no group time
increases in jump height occurred in both the RT- interactions were detected in the EMGrms of VL
WBV (115.0 10.5%, P 5 0.005) and RT groups (P 5 0.54); however, significant time effects were
(111.3 8.2%, P 5 0.001). observed (Po0.001) between the pre-training and
mid-training (P 5 0.014) and pre-training and post-
training (P 5 0.01) sEMG measurements.
Maximal voluntary isometric knee extension force
A significant group time interaction was also ob-
served in maximal isometric knee extension force Maximal isokinetic strength tests
(Table 3), as marked increases in strength from pre- As was observed for isometric knee extension force, a
training levels were observed following the 13-week significant group time interaction was also de-
training in both the RT-WBV (163.5 53.9%, tected in maximal concentric knee extension torque
Po0.001) and RT groups (125.6 13.9%, (Table 3). A comparison of the pre-training and post-
P 5 0.001). Notably, maximal isometric knee exten- training strengths revealed a significant increase in
sion force was significantly higher in the RT-WBV the RT-WBV group (176.7 53.8%, Po0.001),
group than the RT group at both the mid-training whereas no significant changes were found in the
and post-training evaluation points (P 5 0.009 and RT group (117.8 27.8%, P 5 0.18). The analysis
Po0.001, respectively). also demonstrated that maximal concentric knee
extension torque was significantly higher in the RT-
WBV group than the RT group after completion of
sEMG the 13-week training program (P 5 0.007).
To examine the intensity of muscle contractions In contrast to concentric knee torque, no group
under the two training conditions, sEMG signals time interactions were observed in maximal eccentric
from the VM and VL muscles were monitored during knee extension torque (Table 3); however, a signifi-
the maximal isometric extension force test. A sig- cant time effect was found (Po0.001). Similar results
nificant group time interaction was observed in the were observed for the local muscle endurance, as no
7Osawa & Oguma
Table 3. Effects of whole-body vibration on performance tests
RT-WBV (n 5 16) RT (n 5 16) P-value
CMJ (cm)
Pre 24.5 8.6 23.4 7.0 *
Mid 26.9 8.5 24.4 7.4
Post 27.9 8.6 25.8 6.9
ISOM-K (N/kg)
Pre 5.7 1.4 5.5 0.8 ***
Mid 7.6 1.2 6.4 1.3
Post 8.8 1.1 6.8 1.2
CON (N m/kg)
Pre 1.1 0.2 1.3 0.2 ***
Mid 1.6 0.4 1.5 0.5
Post 1.9 0.5 1.5 0.4
ECC (N m/kg)
Pre 1.9 0.4 1.9 0.5
Mid 2.2 0.5 2.1 0.5 Fig. 5. Effects of whole-body vibration (WBV) on surface
Post 2.5 0.6 2.2 0.5 electromyography activities during the maximal isometric
TW (J) knee extension strength test. Measurements were made in the
Pre 1036 374 1213 461 *** pre-training period (Pre), after 7 weeks of training (Mid),
Mid 1126 333 1266 546 and at the completion of the 13-week training program
Post 1242 445 1344 478 (Post). All values are presented as the mean SD. Black
MP (W) bars represent the resistance training with WBV group (RT-
Pre 34.1 11.9 36.9 14.5 WBV), and white bars represent resistance training group
Mid 34.8 10.7 42.4 17.1 (RT). VL, vastus lateralis; VM, vastus medialis. wSignificant
Post 39.6 13.3 41.9 15.2 group time interaction (Po0.05, two-way repeated-mea-
ISOM-L (N m/kg)
sures ANOVA). *Significant difference (Po0.05, Bonferroni
Pre 3.4 1.2 3.4 1.2 **
correction). zSignificant time interaction (Po0.05, two-way
Mid 4.5 1.4 3.8 1.2
Post 4.9 1.4 4.1 1.2 repeated-measures ANOVA).
Sit-up (times)
Pre 15.0 6.7 15.9 5.4
Mid 20.9 6.3 21.0 7.7
Post 23.9 7.0 23.6 7.6 muscle endurance revealed that both groups had
Significant group time interactions are marked as follows: significant increases in the number of sit-ups per-
*Po0.05; **Po0.01; ***Po0.001. formed with respect to time (Po0.001). However,
Pre, pre training program; Mid, post 7-week training period; Post, post the observed changes in abdominal muscle endur-
13-week training period; CMJ, countermovement-jump height; CON, ance did not represent significant group time inter-
concentric contraction; ECC, eccentric contraction; ISOM-K, isometric actions (Table 3).
knee extension force; ISOM-L, isometric lumbar extension torque; MP,
mean power in endurance test; RT, resistance training; RT-WBV,
resistance training with whole-body vibration; TW, total work in endur- Anthropometry, physical activity, and nutritional
ance test. assessment
No significant group time interactions were ob-
group time interactions were observed in total served in the body mass (P 5 0.50), total energy
work (J) or mean power (W) (Table 3), although intake per day (P 5 0.83), or the ratio (%) of pro-
the time effects were found to be significant for both tein:fat:carbohydrate consumed during the trial; pro-
total work (P 5 0.003) and mean power (P 5 0.002) tein (P 5 0.43), fat (P 5 0.17), and carbohydrate
on comparison of pre-training and post-training (P 5 0.41). In addition, no group time interactions
levels. were observed in physical activity (P 5 0.13); how-
ever, physical activity significantly differed between
the pre-training and post-training levels (P 5 0.01).
Trunk muscle strength and endurance
The final performance tests measured isometric lum-
bar extension strength and abdominal muscle endur- Correlation analyses
ance. A significant group time interaction was A significant correlation was observed between per-
observed in the isometric lumbar extension torque, cent change in maximum isometric knee extension
with both the RT-WBV and RT groups displaying force and EMG activity in the RT-WBV group
marked increases in post-training muscle strength (r 5 0.67, Po0.001). However, no significant corre-
compared with baseline values (151.5 34.1%, lation was found between the percent change in
Po0.001 and 126.4 17.5%, Po0.001, respec- muscle force/torque and CSA [lumbar extension
tively) (Table 3). The evaluation of abdominal torque and erector spinae muscle (r 5 0.42,
8Vibration training effects on muscle fitness
P 5 0.11); m. psoas major and countermovement- for exercise protocols combined with WBV (fre-
jump (r 5 0.35, P 5 0.28)]. In the RT group, no quency, 35 Hz; amplitude, 2 mm) in individuals
significant correlations were observed between the with normal body mass. Furthermore, our training
percent change in muscle force/torque and EMG regimen mainly consisted of exercises performed in
activity or muscle CSA. prone and supine positions, resulting in close proxi-
mity of the trunk muscles to the WBV source with
minimal dampening. Although the optimal relation-
Discussion ship between vibration parameters, weight condi-
tions (total mass of body mass and additional
In our randomized controlled study composed of weight), and exercise position remains unclear, these
healthy, untrained adults, a 13-week slow-velocity factors appear to be related with the marked muscle
RT program involving light external loading com- fitness improvements associated with WBV.
bined with WBV resulted in considerable gains in the The observed effects of WBV on muscle hypertro-
CSA of abdominal muscles, and increases in max- phy may involve a number of physiological mechan-
imal isometric knee extension force, isokinetic knee isms. First, the exogenous stimulation of skeletal
extension torque, isometric lumbar extension torque, muscle with vibration may contribute to increases
countermovement-jump height, and EMG activities in muscle mass. This speculation is supported by the
compared with the identical RT without WBV. The study of Xie et al. (2008), who found that daily
present results suggest that WBV has marked addi- (15 min/day) WBV exposure for 8 weeks (5 days/
tional effects on muscle hypertrophy and strength in week) without any exercises or stretching led to
abdominal muscles, and may be suitable for combin- increases of 24% and 29% in type I and II fibers,
ing with slow-velocity RT involving exercises of long respectively, in soleus muscles compared with age-
duration ( 80 s). matched controls. Second, WBV might enhance the
The RT regimen used in this study consisted of effects of RT on muscle hypertrophy by augmenting
eight different lower extremity and trunk muscle muscle activity. It has been suggested that WBV
exercises performed for 80 s with slow velocity, with leads to increases in exercise-induced growth hor-
the exception of the roll back and hip walking mone responses via activation of the hypothalamus–
exercises that were performed continuously for 64 pituitary axis by afferent signals from both muscle
and 48 s, during an approximately 60 min session. metaboreceptors and mechanoreceptors (Kjaer,
Marked effects on muscle strength and power were 1992; Rittweger, 2010). It has also been proposed
also reported in the study conducted by Delecluse et that WBV leads to muscle deoxygenation, which is
al. (2003), who utilized a 20 min WBV-RT program associated with the production of free radicals and
composed of 60 s body-weight exercises with 5 s reactive oxygen species, stimulating satellite cells to
intermittent rest periods over a 12-week period. In regenerate muscle fibers (Anderson, 2000; Yamada et
the RT regimens used by researchers who did not al., 2005). Although it is suggested that a continually
find any additional effects of WBV on muscle generated MVC of 440% during exercises is neces-
strength and power, either light exercises with low sary for muscle growth (Tanimoto & Ishii, 2006), we
volume (5–8 min/session) or high-intensity training found that muscle contractions during exercise with
with short-exercise duration (approximately 30 s/set) WBV were occasionally o40% MVC after applying
were performed (de Ruiter et al., 2003; Ronnestad, a band-stop filter. Although the application of band-
2004; Kvorning et al., 2006; Carson et al., 2010; von stop filters will result in an underestimation of the
Stengel et al., 2010). These findings suggest that the true magnitude of neuromuscular responses to WBV,
additional effects of WBV may be dependent on the muscle activities with WBV after filtering of the
training regimen, particularly the duration of WBV EMG signals remained higher than those without
exposure and the intensity of training. WBV during exercise. In addition, a recent study
In addition to including exercises of longer dura- measuring muscle length and EMG activity during
tion, our training regimen was designed to examine exercise with WBV has shown that EMG changes
the influence of external weight loading and exercise precede muscle lengthening (Cochrane et al., 2009),
position on the augmentation of WBV effects on suggesting that stretch reflex would occur on expo-
muscle. Two studies have reported that the frequency sure to WBV. Although further studies are needed to
and amplitude of vibration platforms or additional provide mechanistic insights for the additional effects
weight loading have effects on force generation (Pel of WBV on muscle hypertrophy (e.g., protein turn-
et al., 2009; Rittweger, 2010). We confirmed pre- over and/or intracellular anabolic signaling from
viously that force generation increases when weight is muscle biopsies), our results suggest that WBV leads
loaded on the vibration platform (Osawa et al., to additional gains in muscular CSA.
2011b). Our present results indicate the possibility In line with the induction of muscle hypertrophy
that light external weight loading would be suitable resulting from WBV, maximal isometric and
9Osawa & Oguma concentric contractions, in addition to power, were Several limitations of this study should be consid- also increased by incorporating WBV into the ered when interpreting and generalizing the findings 13-week RT regimen. Notably, however, maximal presented here. First, we did not obtain MRI data eccentric contraction and local muscle endurance from quadriceps muscles due to budget restraints. were not noticeably affected by WBV. The finding Second, EMG was not applied to the evaluation of that additional WBV effects were observed only in a antagonist muscles and the power and trunk muscle few muscle performance gains might be attributable strength tests due to a lack of instruments for to the higher sensitivity of the neuromuscular sys- synchronizing muscle power and EMG signals, and tems involved in isometric and concentric contrac- because the waist pad of the lumbar extension tions, and countermovement-jump to WBV, leading machine was located at an identical level as the to increased co-activation of a–g motor neurons electrode positions. Finally, although the partici- (Burke et al., 1978; Romano & Schieppati, 1987; pants were randomly assigned to training groups Kouzaki et al., 2000; Fallon & Macefield, 2007). As stratified by age and sex, the study consisted pre- an earlier study found that exercise with vibration dominantly of women with a relatively wide range of significantly improved maximal force (149.8%) after ages. As age and sex might be effect modifiers of a 3-week training period, it has been suggested that muscle strength and power gains, a larger study size RT combined with WBV would lead to increases with a higher proportion of men and smaller age in muscle strength primarily due to enhancement of range is needed to confirm that the observed in- neural factors (Issurin et al., 1994). We detected creases in strength are applicable to both males and a significant correlation between elevated EMG females. amplitude and knee extension force gain in the RT- In conclusion, we have demonstrated that a 13- WBV group. The elevated EMG activity reflects week RT program combined with WBV leads to increased recruitment and firing rate of motor units, considerable gains in the CSA of abdominal muscles, and would contribute to increased muscle force maximal isometric and concentric knee extension (Suzuki et al., 2002). In contrast, we did not detect strengths, isometric lumbar extension strength, and a correlation between the increase in the CSA of m. countermovement-jump height over baseline values psoas major and countermovement-jump height in untrained adults compared with the identical improvement, which may have been due to the training lacking WBV. In particular, the WBV-in- numerous skeletal muscles that contribute to the duced increases in the CSA of m. psoas major and movement, or between the increase in the CSA of erector spinae muscle, and the maximal isometric erector spinae muscle and lumbar extension torque lumbar extension strength gains, suggest that incor- gain. As we did not observe muscle hypertrophic poration of WBV into RT programs may be bene- effects on lower extremity muscles or on neural ficial for the prevention and rehabilitation of chronic improvement in abdominal muscles, we could not low back pain. provide solid evidence for the contribution of muscle hypertrophy on the observed strength gains. How- ever, the present results suggest that the observed Perspectives strength gains might be attributable to the stimula- tion of neural factors by WBV. Our findings confirm that intentional slow-velocity In the present study, weight loading was based on RT combined with WBV has marked training effects individual body mass due to safety concerns that on muscle hypertrophy, strength, and power in untrained individuals could correctly perform the healthy, untrained adults. The combined training target exercises on the moving vibration platform method takes advantage of the force generated by with standardized weight limits. Under unstable the vibration platform (Rittweger, 2010) and stimu- conditions, there was also concern that certain parti- lation of the tonic vibration reflex response in cipants might perform exercises without adequate muscles (Hagbarth & Eklund, 1966). In future training intensity, resulting in variations in muscle studies, it would be interesting to determine whether strength and power gains in the RT-WBV group. the efficacy of vibration is increased when combined However, in both training groups, participants per- with RT exercise protocols that subject muscles to ceived the exercises as physically demanding increasing time under tension. In practical applica- and experienced fatigue, light to moderate delayed tions, the significant increases in the CSA of m. onset of muscle soreness following each training psoas major muscle and the ability to obtain higher session, and improved muscle fitness. Thus, we maximal isometric lumbar extension torque with have confidence that the training intensity was prop- vibration may be beneficial for the prevention of erly configured in this study, a speculation that is sarcopenia and rehabilitation of low back pain, supported by the muscle fitness gains observed in which is associated with the deterioration of these both groups. parameters (Cassisi et al., 1993; Barker et al., 2004). 10
Vibration training effects on muscle fitness
As RT with WBV has also been shown to relieve Key words: muscle mass, vibration, novice, platform,
chronic low back pain sensation in the elderly trunk muscle, training program, neural adaptation.
(Iwamoto et al., 2005), our promising results
support the need to further investigate the
effects of WBV on chronic musculoskeletal pain Acknowledgement
sensation and strength in young to middle-aged This study was supported by the Keio University Doctoral
individuals. Student Grant-in-Aid Program, 2009.
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