Effects of individualized whole-body vibration on muscle flexibility and mechanical power

Abstract

The first purpose of the present study was to assess acute, residual and chronic effects of whole-body vibration on hamstring and lower back flexibility through the application of an individual frequency of vibration. The second purpose was to determine whether the applied vibration intervention over time influences flexibility and reactive strength differently.
Thirty-four young physically active subjects (19 female and 15 male) were randomly assigned to either a Control or a Vibration Group. Lower back and hamstring flexibility was measured using the Stand and Reach Test. The reactive strength was estimated calculating the power in Drop Jump.
During whole-body vibration the relative change in acute flexibility for the Vibration Group (5.30+/-1.67 cm, 284%) reached a level of significance (P=0.038) compared to that of the Control Group (3.14+/-2.11 cm, 84%). Statistically significant differences in residual flexibility between the two groups were found at 6-min after the conclusion of vibration (P=0.034), at which point the Vibration Group showed the maximal relative change to pre-test (6.31+/-3.36 cm, 138%) versus the Control Group (3.06+/-1.87 cm, 20%). Chronic exposure of whole-body vibration did not produce significant changes in flexibility over time (P>0.05), whereas power in the Drop Jump performance of the Vibration Group increased significantly resulting in a benefit of 16% (P=0.019).
The current study shows that individualized whole-body vibration without superimposing other exercises is an effective method of acutely increasing lower back and hamstring flexibility. Furthermore, the applied individualized whole-body vibration over time influences the reactive strength rather than flexibility.

Full text

MINERVA MEDICA
COPYRIGHT®
J SPORTS MED PHYS FITNESS 2010;50:139-51
Effects of individualized whole-body vibration
on muscle flexibility and mechanical power
Aim.The first purpose of the present study was to assess acute,
residual and chronic effects of whole-body vibration on ham-
string and lower back flexibility through the application of an
individual frequency of vibration. The second purpose was to
determine whether the applied vibration intervention over
time influences flexibility and reactive strength differently.
Methods.Thirty-four young physically active subjects (19 female
and 15 male) were randomly assigned to either a Control or a
Vibration Group. Lower back and hamstring flexibility was
measured using the Stand and Reach Test. The reactive strength
was estimated calculating the power in Drop Jump.
Results. During whole-body vibration the relative change in
acute flexibility for the Vibration Group (5.30±1.67 cm, 284%)
reached a level of significance (P=0.038) compared to that of the
Control Group (3.14±2.11 cm, 84%). Statistically significant dif-
ferences in residual flexibility between the two groups were
found at 6-min after the conclusion of vibration (P=0.034), at
which point the Vibration Group showed the maximal relative
change to pre-test (6.31±3.36 cm, 138%) versus the Control
Group (3.06±1.87 cm, 20%). Chronic exposure of whole-body
vibration did not produce significant changes in flexibility over
time (P>0.05), whereas power in the Drop Jump performance
of the Vibration Group increased significantly resulting in a
benefit of 16% (P=0.019).
Conclusion.The current study shows that individualized whole-
body vibration without superimposing other exercises is an
effective method of acutely increasing lower back and ham-
string flexibility. Furthermore, the applied individualized
whole-body vibration over time influences the reactive strength
rather than flexibility.
K
EY WORDS
:Vibration - Muscle strength - Exercise.
T
he application of mechanical vibration to the
human body as a specific training method is
becoming popular for the development of muscle
strength, flexibility, and power.1-22 The first application
of vibration was conducted by Granville in 1881 22 in
the treatment of pain and subsequently employed in
physical therapy to raise the excitability of the alpha
and gamma motoneuron pools, thus permitting the
patient to achieve greater voluntary control.23, 24 The
theory behind this treatment was developed by Eklund
and Hagbarth,16 who found that the vibration of the
muscle induces a reflex mechanism, called tonic vibra-
tion reflex, which in turn results in an increase in
muscle tension.
Mechanical vibration is characterized by an oscil-
latory motion produced with specially designed vibrat-
ing plates 6, 25-37 (whole-body vibration) or vibrating
cables and dumbbells if the stimuli involves a spe-
cific muscle.5, 22 The amplitude of vibration (in mm),
the repetition rate of the cycles of oscillation (fre-
1Faculty of Sport Sciences,University of L’Aquila
L’Aquila, Italy
2Department of Sport Sciences, National Olympic Committee
Rome, Italy
3Department of Physics, University of L’Aquila
L’Aquila, Italy
4Department of Internal Medicine and Public Health
Faculty of Medicine, University of L’Aquila, L’Aquila, Italy
5Department of Biomechanics
Faculty of Physical Education and Sport Sciences
Semmelweis University, Budapest, Hungary
Acknowledgments.—We thank the Faculty of Sport Science of L’Aquila
(Italy), which has supported this study. The cooperation of the subjects is
greatly appreciated. We disclose any professional relationship with the
Ergotest Europe and Bosco System. The results of the present study do not
constitute endorsement of the product by the authors.
Corresponding author: R. Di Giminiani, Viale Adriatico 25, 64013
Corropoli (TE), Italy. E-mail: mailto:digi.e@tiscali.it
R. DI GIMINIANI 1, R. MANNO2, R. SCRIMAGLIO1-3, G. SEMENTILLI4, J. TIHANYI 5
Vol. 50 - No. 2 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 139

MINERVA MEDICA
COPYRIGHT®
DI GIMINIANI EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION
140 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS June 2010
quency of vibration, in Hz) and the magnitude (accel-
eration, m/s2) are the biomechanical parameters which
determine the workload.27 Vibrations have been applied
using frequencies from 15 to 44 Hz, displacements
from 2 to 10 mm, and acceleration ranging from 3.5
to 15 g.9
The effects of vibration on muscle strength and pow-
er have been extensively examined using different
treatment protocols following acute, residual,4, 6, 11,
30, 35, 38 and chronic exposure 3,12,13,15,31,32,36,37 using
different types of vibratory methods.
Inversely, applying mechanical vibration as a modal-
ity for increasing flexibility has been presented by
only a few experiments.10, 17, 22, 23, 33, 39 Issurin et al.22
noted a chronic post-vibration effect on flexibility by
superimposing local vibration (vibrating cable) with
conventional stretching exercises. A similar method,
conducted by Sands et al.33 revealed a residual and
long-term influence of vibratory stimulation (vibra-
tory device) on flexibility in young highly trained
gymnasts who carried out stretching exercises during
vibration. Both studies confirmed the hypothesis that
vibration could induce an additional positive effect
on flexibility by relaxing the stretched muscle. The
mechanisms underlined by the authors were based on
presynaptic inhibition of group Ia afferent fibres or a
“busy line” phenomenon that is created when both
vibration stimulation and stretching influence the same
Ia pathways. In addition, combining a strong stretch
stimulus and vibration may result in Golgi tendon
organ activation via Ib pathways resulting in auto-
genic inhibition of the vibrated muscle.22, 33
Recently, enhancement on hamstring flexibility
through the application of whole-body vibration has
also been reported after both acute 10, 23 and chronic
treatment.17, 39
During whole-body vibration the subjects stand on
a vibrating plate with their feet placed on either side of
the axle, maintaining a steady position while the oscil-
lations of the platform produces a vertical ground reac-
tion force. Whole-body vibration assumes that a ton-
ic vibration reflex is elicited similarly to the direct or
indirect application of vibration on muscles or ten-
dons. The residual enhanced flexibility following one
session of whole-body vibration 10, 23 suggests that
vibration exposure may activate the Ia inhibitory
interneurones of the antagonist muscle.18 Consequently,
chronic exposure may lead to changes in intramuscu-
lar coordination thus reducing the braking force around
the hip and lower back joints, which could subse-
quently potentiate sit and reach scores and the reactive
strength.17, 39
However, in these studies the frequency of vibra-
tion during whole-body vibration was pre-selected
rather than individually determined for each subject by
using the EMG muscle response.15 We hypothesized
that an individual frequency of vibration should opti-
mize the functional activation of the primary endings
of the muscle spindle which, by exerting an excitato-
ry influence on agonist alpha motoneurones (agonist
muscle contraction) and a inhibitory influence on
antagonist motoneurones,18 would increase flexibili-
ty and reactive strength.
Current literature lacks the effect of whole-body
vibration during stimulation. Moreover, flexibility
played only a marginal role in the experimental design
of the aforementioned studies.
Up to now studies have assessed the enhancements
on flexibility with just two measurements (pre-post
treatment). Our study was designed in such a way as
to construct a kinetics of the flexibility in acute (dur-
ing treatment) and immediately after one session of
vibration treatment in order to better understand the
neural process involved and consequently develop
practical applications.
Therefore, the aims of the present study were: 1) to
assess acute, residual and chronic effects of whole-
body vibration on hamstring and lower back flexibil-
ity in young physically active subjects through the
application of an individual frequency of stimulation;
and 2) to determine whether the applied vibration
intervention over time influences flexibility and reac-
tive strength differently.
Materials and methods
Subjects and experimental design
The study procedures, including: recruitment, mea-
surements and intervention were performed in the
Faculty of Sport Sciences, University of L’Aquila,
Italy. Among the 200 second year students of the sport
sciences faculty a total of 40 subjects (20 males; 20
females) were enrolled (Figure 1). Exclusion criteria
included a history of back pain, acute inflammation in
the pelvis and/or lower extremities, acute thrombosis,
bone tumours, recent fractures, recent implants, gall-

MINERVA MEDICA
COPYRIGHT®
Vol. 50 - No. 2 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 141
EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION DI GIMINIANI
stones, kidney or bladder stones, any disease of the
spine, peripheral vascular disease or pregnancy, and
sever delayed onset of muscle soreness of hamstring
muscles. Subjects were randomly assigned to either the
Acute and Residual Flexibility Group or the Chronic
Flexibility Group using a stratified randomization
technique, according to gender (since this may be a fac-
tor in flexibility determination), with 10 males and 10
females in each Group. Subsequently, subjects in each
Group were assigned to either the Vibration Group or
the Control Group using the same stratified random-
ization technique (Figure 1).
Following approval by the University’s Ethics
Committee, all subjects provided written informed
consent. During the follow-up study 6 subjects with-
drew due to loss of interest. The subject characteristics
for those who completed all the test sessions are pro-
vided in Table I. The study began investigating the
acute effects of vibration intervention on March 2004
and the residual effects were recorded in April. To
conclude the study, the chronic effects of vibration
intervention were completed from May to July 2004.
Although the same subjects participated in both acute
and residual effects of the vibration treatment, all the
measurements were repeated; in acute, residual, and
chronic. During the follow-up (chronic exposure), all
Population
(N.=200)
Screened
(N.=40)
Randomized
(N.=40)
Randomized
(N.=20)
Chronic flexibility group
(N.=20)
Analyzed=9
Lost to follow-up=1 Analyzed=9
Lost to follow-up=1
Analyzed=8
Lost to follow-up=2 Analyzed=8
Lost to follow-up=2
Control group
(N=10) Vibration group
(N=10) Control group
(N=10) Vibration group
(N=10)
Randomized
(N.=20)
Acute and residual flexibility group
(N.=20)
Figure 1.—Flow diagram.

MINERVA MEDICA
COPYRIGHT®
DI GIMINIANI EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION
142 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS June 2010
subjects were engaged in systematic physical activities
(swimming, gymnastics, and track and field activi-
ties) at least three times a week.
Vibrating platform and flexibility test
The subjects underwent vertical sinusoidal whole-
body vibration using a vibratory platform (Nemes-
Lsb, Bosco-System, Rieti, Italy). The subjects stood on
the platform at an angle of 90° between the lower and
upper leg, while grasping a railing in front of them
(Figure 2). The appropriate toe and heel positions were
marked on the platform to ensure consistency of foot
position and orientation among trials. The vibrating
platform was modified in order to allow the subjects to
perform the stand and reach test on the same plate.
Toe and heel positions were also marked in order to
define the positioning of the feet for testing, resulting
in two different positions. This double foot position on
the plate permitted the subjects to change their position
easily on the plate; from a standing crouched position
(vibration intervention) to a stand and reach test, par-
ticularly when determining flexibility during acute
exposure (Figure 3). The stand and reach test was con-
ducted on the vibrating plate with the feet placed
against a graduated rules. The knees were held extend-
ed by the tester. The subjects leaned downward slow-
ly as far as possible toward a graduated rules from -20
to +20, holding the greatest stretch for 2 seconds. The
tester had to be sure that there were not jerky move-
ments on the subject and that her/his fingertips
remained at the level. The score was recorded as the
distance before (negative) or beyond (positive) the
toes.
TABLE I.—Subjects characteristics.
Characteristic Acute and residual flexibility group Chronic flexibility group
(mean±SD) (N.=16) (N.=18)
Males/Females Vibration group Control group Vibration group Control group
(M/F) (N=8; 4 M/4 F) (N=8; 3 M/5 F) (N=9; 4 M/5 F) (N=9; 4 M/5 F)
Age (years) 19.75±1.38 20.50±1.90 21.00±1.50022.22±1.85
Height (cm) 168.87±5.61 170.80±10.65 169.22±7.060166.88±7.34
Weight (kg) 63.53±8.59 67.22±10.72 65.27±10.20 62.88±9.61
Figure 2.—Position adopted by the subjects on the vibrating plate. Figure 3.—Stand and reach test performed by the subjects.

MINERVA MEDICA
COPYRIGHT®
Vol. 50 - No. 2 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 143
EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION DI GIMINIANI
Estimation of optimum vibration frequency and EMG
analysis
The subjects performed the test assuming the posi-
tion presented in Figure 2. The peak-to-peak dis-
placement of vibration was about 2 mm. The vertical
component of acceleration was measured using an
accelerometer (Type ET-Acc-02, Ergotest Technology,
Langesund, Norway) placed in the middle of the vibra-
tion platform during a progressive incremental fre-
quency protocol from 20 to 55 Hz. The acceleration in
this test ranged from 1.1 to 53.6 m s-2. The frequency
of the vibrations was determined for each participant
of the individual-vibration group by monitoring the
EMGrms activity of the vastus lateralis muscle (domi-
nant leg) during trials performed at different frequen-
cies. The participants performed an isometric half
squat in the following conditions: no vibrations (i.e. 0
Hz), and randomly at 20, 25, 30, 35, 40, 45, 50, and 55
Hz with a 4 minute pause between each trial, with
each trial lasting 20 s as described by Di Giminiani et
al.15 The frequency of vibration corresponding to the
highest neuromuscular response (EMGrms activity)
recorded during the trials was then used for the vibra-
tion intervention in acute, residual and chronic expo-
sure (Figure 4, Table II). The EMG sensors and
accelerometer were connected to a data collection unit
(Muscle-Lab, Ergotest Technology, Langesund,
Norway) which, in turn, was connected to a personal
computer via the USB port.
The EMG activity was recorded using bipolar surface
electrodes (inter-electrode distance: 2.0 cm) including
an amplifier (gain at 100 Hz: 1000; input impedance:
2GΩcommon mode rejection rate: 100 dB; input noise
level [1 kHz band]: 20 nV Hz-2) and a Butterworth
band-pass filter (3-dB low cut-off frequency: 8 Hz; 3-
dB high cut-off frequency: 1200 Hz) fixed longitudi-
nally over the muscle belly. The EMG cables were
secured (the subjects wore a suit next to the skin) to pre-
vent motion artifact. The pre-amplified EMG signals
were first converted to a root mean square and then
sampled at 100 Hz. The averaged root mean square
was expressed as a function of time in millivolts.
250
200
150
100
50
05550454035302520
Frequency (Hz)
160
80
60
40
20
05550454035302520
Frequency (Hz)
100
120
140
Figure 4.—The EMGrms of the vastus lateralis (dominant leg) recorded
during different vibration frequencies normalized to the baseline isome-
tric value. The subjects performed an isometric half-squat in the following
conditions: no vibration, and 20, 25, 30, 35, 40, 45, 50, and 55 Hz vibra-
tion frequencies in random order. In the upper panel are reported the mean
values and standard deviations of all subjects that were exposed to vibra-
tion. In the bottom panel is shown the representative data for the subject
01.
TABLE II.—Individual frequencies of vibration used during the vibra-
tion exposure. Subjects of the Vibration Group with number from 01
to 08 participated in the Acute and Residual Flexibility Group,
whereas subjects with number from 09 to 17 took part in the Chronic
Flexibility Group.
Subjects (N) Frequency of vibration (Hz)
01 45
02 35
03 20
04 45
05 30
06 40
07 40
08 30
09 55
10 45
11 35
12 35
13 35
14 55
15 30
16 35
17 45
Mean 37.9
DS 9.4

MINERVA MEDICA
COPYRIGHT®
DI GIMINIANI EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION
144 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS June 2010
Vibration intervention
All the subjects stood on the vibration platform in
exactly the same body position (Figure 2) and the
vibration frequency was set individually for each sub-
ject as described previously. The vibrating platform
was turned off for the Control Group.
ACUTE AND RESIDUAL FLEXIBILITY
The subjects of the Vibration Group who were test-
ed for acute and residual flexibility, underwent 10
series of 1-min (10×1) whole-body vibration with a 1-
min pause between series and a 4-min pause after the
first five series of vibrations (5×1).
CHRONIC FLEXIBILITY AND REACTIVE STRENGTH
The members of Vibration Group were exposed to
whole-body vibration three times a week (on Monday,
Wednesday, Friday) for 8 weeks (Table III). The train-
ing session was the same as that applied to test acute
and residual effect (see above).
Test procedures
ACUTE FLEXIBILITY
All subjects underwent a pre-test using the stand
and reach test (the mean value of 3 measurements was
recorded) in order to assess muscle flexibility. The
test was repeated in the last 10 seconds of each series
of 1-minute performed by the subjects on a vibrating
platform. Ten measurements of flexibility were carried
out for each group performing the stand and reach test
on the same vibrating platform. For subjects of the
Control Group, however, the vibrating platform was
turned off.
RESIDUAL FLEXIBILITY
A pre-test was performed by all subjects using the
stand and reach test (the mean value of 3 measure-
ment was recorded) in order to assess muscle flexi-
bility. The test was repeated for the subjects of the
Vibration Group immediately after the first five series
of whole-body vibration, and then after 2 and 4 min-
utes. This was followed by a 4-minute pause after
which the subjects completed the session of treat-
ment (other 5 series), and the stand and reach test was
performed at 0, 2, 4, 6, and 8-minutes after the end of
vibration intervention. The same procedure was adopt-
ed for the Control Group but the vibrating platform
was turned off.
CHRONIC FLEXIBILITY AND REACTIVE STRENGTH
The subjects were tested on four occasions at the
same time of day, and were required to refrain from
any tiring physical activity in the 2 days preceding the
test. Measurements were made before starting the
whole-body vibration intervention, after 4 weeks of
treatment, after 8 weeks of treatment, and then 1-week
following the conclusion of vibration treatment.
Each test session began with the measurement of
anthropometric characteristics. Next, each subject
performed the stand and reach test on the vibrating
plate (Figure 3). The mean value of three measure-
ments was recorded. Subsequently, they completed a
10-min warm-up (6 min running on a treadmill at a
speed of 6 km·h-1 and 4 min stretching) before per-
forming a series of drop jumps on a resistive plat-
form (Ergojump-Bosco System, Rieti, Italy). The
best performance dropping from 20-30-40-50- and 60
cm was recorded.7The centre of mass displacement,
flight time, and contact time were also recorded.
Mean power, P (in W·kg-1), was calculated according
to Bosco’s formula.8
Reliability of measurements
The reliability of measurements taken on the same
day was 0.92 (CV=2.2%) for estimation of individ-
TABLE III.—Characteristics of whole-body vibration treatment during
chronic exposure.
Training volume and intensity of the vibration treatment Values
Volume
Total duration of vibration in one session (min) 10
Number of series 10
Duration of one series (s) 60
Number of session training in one week 3
Total number of session training 24
Total duration of vibration in 8-weeks (min) 240
Intensity
Rest period after the first five series (min) 4
Rest period between series (s) 60
Rest period between two training sessions (days) 1-2
Vibration amplitude (mm) ~1
Vibration frequency (Hz) From 20 to 55

MINERVA MEDICA
COPYRIGHT®
Vol. 50 - No. 2 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 145
EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION DI GIMINIANI
ual frequency of vibration and 0.94 on different days
(CV=3.7%) for the drop jump.
The reliability of flexibility measurements taken on
the same day was 0.99 (CV=2.2%) for acute analy-
sis, 0.99 (CV=2.4 %) for residual analysis, and 0.97 on
different days (CV=3.6%) for chronic analysis.
Statistical analysis
Conventional statistical methods were employed,
including mean values, standard deviations (SD), and
percentages (%). The relative change percentage was
calculated in each subject and the mean values were
then calculated. The acute, residual, and chronic effect
of intervention time of whole-body vibration
(Independent variable) on flexibility and reactive
strength (dependent variables: stand and reach test, and
power during the drop jump) were assessed over the
course of the test sessions by means of the Friedman
test in each group and by using a Nemenyi bilateral test
for within-group comparisons to locate differences.
Bonferroni correction was used to adjust the P-value
in relation to the number of contrasts performed. The
comparisons between groups were made using the
Mann-Whitney test.
The reliability of the measurements was calculated
using intra-class correlation (Cronbach’s alpha coef-
ficient to determine between-subjects reliability) and
the typical percentage error (to determine the within-
subjects variation) as reported by Hopkins.21 All analy-
ses were executed using the AddinsoftTM XLSTAT
(version 2009.4.07). Statistical significance was set
at P ≥0.05.
Results
Acute flexibility
The Vibration Group progressively increased in
flexibility and significant differences (P=0.0009) were
found in the 5th (from pre-test: 3.95±1.62 cm), in the
6th (from pre-test: 4.04±1.55 cm), in the 7th (from pre-
test: 4.47±1.81 cm), in the 8th (from pre-test: 5.02±1.19
cm; from 1st series: 3.75±1.55 cm), in the 9th (from
pre-test: 5.30±1.67 cm; from 1st series: 4.03±1.70
25
20
15
10
5
01st
Pre Recovery
4 min
-5
2nd 3rd 4th 5th 6th 7th 8th 9th 10th
Vibration group
Control group
Vibration group
*
***
*
*
** *
** *
**
Series
Figure 5.—Acute effect during 1 session of whole-body vibration (mean values±SD). The subjects underwent 10 series of 1-min (10×1) with a 1-min
pause between series and a 4-min pause after the first five series (5×1). The measurements of flexibility were carried out in the last 10 seconds of each
series. *Significant differences from pre-test, P=0.0009; **significant differences from 1st series, P=0.0009; ***significant differences from 2nd
series, P=0.0009.

MINERVA MEDICA
COPYRIGHT®
DI GIMINIANI EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION
146 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS June 2010
cm), and in the 10th series (from pre-test: 4.76±1.76
cm; from 1st series: 3.48±1.71 cm) (Figure 5). The
Control Group showed significant differences
(P=0.0009) in the 5th (from pre-test: 3.02±2.17 cm), in
the 8th (from pre-test: 3.06±2.86 cm), in the 9th (from
pre-test: 3.14±2.11 cm; from 1st series: 2.29±1.38
cm), and in the 10th series (from pre-test: 3.93±2.53
cm; from 1st series: 3.08±1.80 cm; from 2nd series:
2.58±2.15 cm) (Figure 5).
During the 9th series, the maximal relative change
for the Vibration Group (5.30±1.67 cm, 284%)
reached a level of significance (P=0.038) compared
to that of the Control Group (3.14±2.11 cm, 84 %)
(Figure 6).
Residual flexibility
Significant residual effects (P=0.0014) on flexi-
bility were found 4-min (t4) after the conclusion of
the 10 series of whole-body vibration (from pre-test:
5.75±3.91 cm; from t0: 3.56±2.17 cm), as well as 6-
min (t6) after (from pre-test: 6.31±3.36 cm; from t0:
4.12±2.16 cm), and again at 8-min (t8) after (from
pre-test: 5.56±4.41 cm; from t0: 3.37±4.63 cm)
(Figure 7). The Control Group showed significant
differences (P=0.0014) 2-min (t2) after the conclusion
700
500
300
100
-100 Vibration group Control group
*
*
**
Post
Pre
Figure 6.—Relative change on acute flexibility during 1 session of who-
le-body vibration. The maximal differences was observed in the 9th series
in both groups. *Significant differences from pre-test, P=0.009; **signi-
ficant differences between the groups, P=0.038.
20
15
10
5
0
Pre WBV
(5 min)
-5
Vibration group
Control group
Vibration group
WBV
(5 min) t0 t2 t4 t0 t2 t4 t6 t8
** * *
**
Figure 7.—Residual effect after 1 session of whole-body vibration (mean values±SD). The flexibility was assessed pre and at 0, 2, and 4 min (t0, t2,
t4) after the end of the first five series, and at 0, 2, 4, 6, and 8 min after the end of 10 series (t0, t2, t4, t6, t8). *Significant differences from pre
P=0.0014; **significant differences from t0 (after 5-min), P=0.0014.

MINERVA MEDICA
COPYRIGHT®
Vol. 50 - No. 2 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 147
EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION DI GIMINIANI
of the 10 series on the vibrating plate (from pre-test:
3.00±1.98 cm), as well as 4-min after (from pre-test:
3.12±1.63 cm), 6-min after (from pre-test: 3.06±1.87
cm), and finally at 8-min after (from pre-test:
3.43±1.84 cm; from t0: 1.75±1.55 cm) (Figure 7).
Statistical differences between the two groups were
found at 6-min after the conclusion of vibration
(P=0.034), at which point the Vibration Group showed
the maximal relative change to pre-test (6.31±3.36
cm, 138 %) versus the Control Group (3.06±1.87
cm, 20%) (Figure 8).
CHRONIC FLEXIBILITY AND REACTIVE STRENGTH
Chronic exposure of whole-body vibration did not
produce significant changes in flexibility over time
(P>0.05) (Figure 9), whereas power in the Drop Jump
performance (1-week after the end of treatment) of
the Vibration Group increased significantly resulting
in a benefit of 16 % (P=0.019) (Figure 10). In com-
parison, the Control Group did not reach a level of
significance (P=0.175).
Discussion
To our knowledge, this is the first study to investi-
gate acute, residual and chronic effects of individual-
ized whole-body vibration on flexibility in young
physically active subjects. The novel aspects of this
investigation include: the effects on flexibility were
assessed during and not only immediately after whole-
body vibration; several measurements were carried
out to construct a kinetics of flexibility during and fol-
*
500
400
300
100
0
*
**
Vibration group Control group
200
Post
Pre
Figure 8.—Relative change on residual flexibility after 1 session of who-
le-body vibration (6-min after the end of treatment). *Significant differences
from pre-test, P=0.009; **significant differences between groups, P=0.034.
Vibration group Control group
18
8
6
2
0Test 1
4
Test 0 Test 2 Test 3
10
12
14
16
Figure 9.—Chronic effect of whole-body vibration on flexibility (mean
values±SD). The test was performed before the treatment (Test0), after 4-
weeks of treatment (Test1), 8-weeks of treatment (Test2), and 1-week
after the end of treatment (Test3).
Vibration group Control group
60
10
0Test 1Test 0 Test 2 Test 3
20
30
40
50
*ns
Figure 10.—Chronic effect of whole-body vibration on Drop Jump (mean
values±SD). The test was performed before the treatment (Test0), after 4-
weeks of treatment (Test1), 8-weeks of treatment (Test2), and 1-week
after the end of treatment (Test3). The Vibration Group showed a signifi-
cant difference from Test0 at Test3. *P=0.019. The Control Group did not
show significant differences, NS: P=0.175.

MINERVA MEDICA
COPYRIGHT®
DI GIMINIANI EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION
148 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS June 2010
lowing exposure to vibration; an individual frequency
of vibration was used.
Unlike, the present study, which used individual-
ized frequencies, previous studies used frequencies
that were fixed or which increased progressively for
each subject during the vibration exposure. We suggest
that the frequency characteristics of whole-body vibra-
tion should be prescribed in an individualized fash-
ion similar to exercise prescription for progressive
resistance exercise in terms of load, number of repe-
titions, and series. There is evidence to suggest, for
example, that the determination of optimal drop height
for drop jump training improved performance in ver-
tical jumps more than non-customized training pro-
tocols.7In the present study, the individual frequency
used during whole-body vibration for each subject
was estimated on the basis of EMGrms activity (Figure
4). An important observation was that the individual
frequencies selected for the treatment varied between
subjects revealing differences among individuals in
their sensitivity to vibration frequency (Table II). In the
bottom panel of the Figure 4, we can see that the high-
est EMGrms response to different vibration frequen-
cies for one subject was recorded at 45 Hz. In this
example, if the subject had been vibrated at 30 Hz,
the widely used frequency of vibration, the EMGrms
activity would have been about 30% less than the
EMGrms that was observed at 45 Hz, the individual
frequency selected for the treatment.
ACUTE FLEXIBILITY
The acute effects of whole-body vibration treatment
resulted in a progressive increase in flexibility that
reached maximum relative change during the 9th min
of treatment (Figures 5,6). This pronounced effect,
was, in part, expected and cannot be compared to oth-
er studies considering that no other research has been
directed at the acute influence of whole-body vibration
on flexibility enhancement. In an attempt to identify the
mechanism that determined the large effect on flexi-
bility in both groups, it is necessary to clarify what
was measured with the stand and reach test and make
an analysis of the position adopted by the subjects on
the vibrating plate.
The stand and reach test protocol allows the indirect
assessment of the influence of the 4 major muscle
groups that affect the scores: erector spinae, hip rota-
tors, hamstrings, and gastrocnemii.20 On the other
hand, the half-squat position adopted by the subjects
was sustained by a moderate isometric contraction
of quadriceps, tibialis anterior, gastrocnemii and glu-
teus muscle. Furthermore, by superimposing whole-
body vibration in this position, a significant enhance-
ment in EMG activity has been revealed in the quadri-
ceps, tibialis anterior, and gastrocnemii but not in the
hamstring muscles.1Whole-body vibration assumes
that the vibration induced in these muscles by a vibrat-
ing plate elicits a tonic vibration reflex similar to the
direct application of vibration on muscles or tendons.
This so-called tonic vibration reflex (TVR) is to a
large extent mediated by IA polysynaptic excitatory
projections to the alpha motoneurones. The motor
effect of muscle vibration in healthy subjects is not
restricted to the muscles undergoing vibration (which
respond with a contraction); the vibration also induces
the relaxation of antagonist muscles, as a sign of a
reciprocal inhibition.18 Increased flexibility could also
be caused by the stimulation of the Golgi tendon organs
(gluteus, and gastrocnemius), which, unlike the mus-
cle spindles, results in inhibition of the contraction,
followed by relaxation of the muscle.18 These mech-
anisms could partially explain the increase in flexi-
bility in our study. The mechanical action of vibra-
tion is to produce fast and brief changes in the length
of the muscle-tendon complex. This perturbation
applied to muscles in a lengthened position (gluteus,
hamstring, and gastrocnemius) over time could have
modified the viscoelastic properties of the muscle-
tendon complex, increased stretch tolerance as with
stretching exercises 19, 29 and/or reduced stretch pain as
there is evidence that vibration has analgesic effects
during and after immediate application of such stim-
uli to the muscle or tendon.26 The influence on the
mechanical properties of the muscle-tendon complex
could also explain the significant enhancement in flex-
ibility observed in the Control Group. In addition to
this, the viscoelastic behavior of the muscle-tendon
complex appears to be insensitive to increases in intra-
muscular temperature in a physiological range.28
Therefore, the enhancement in flexibility seen in the
Control Group should be attributed not to the effects
of warm-up but to the position assumed by the subjects.
RESIDUAL FLEXIBILITY
In a similar manner to acute flexibility, the resid-
ual changes started to increase progressively in both
groups immediately after 5-min on the vibrating plate,
although the level of significance was reached after the

MINERVA MEDICA
COPYRIGHT®
Vol. 50 - No. 2 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 149
EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION DI GIMINIANI
end of the entire 10 minute session, with a maximum
relative increase at 6-min (t6) after the end of treatment
(Figures 7,8). It is interesting to note that the maximum
relative change observed in acute was nearly con-
firmed as residual effect in the Vibration Group, while
the residual effect in the Control Group was less. These
results emphasize the large residual effect of whole-
body vibration on flexibility.
Cochrane et al.10 and Jacobs and Burns 23 reported
a significant improvement of 8.2% and 16.2% respec-
tively in the sit and reach test following 5-min of
whole-body vibration. Sands et al.,33 superimposing
vibrating cushions (vibrating device) on forward split
stretching positions showed a benefit of about 6 cm in
the right rear split position and 7.5 cm in the left rear
split position. However, differences in protocol train-
ing, testing and the number of pre-post comparisons,
makes it difficult to directly compare our results with
these studies. For example, if we had tested the flexi-
bility using a single pre-post comparison after 5 min
of whole-body vibration, the relative change would
have been 81 % (P=0.021) for the Vibration Group
and 34% (P=0.022) for the Control Group. We also
specify that these relative changes were calculated in
each of the subjects and the mean relative change
(reported in section statistical analysis) was then cal-
culated. Alternatively, calculating the relative change
by the mean values, the relative change could be dif-
ferent. In the example reported above the relative
change for the Vibration Group would be 50% and
47% for the Control Group.
Investigations into hamstring flexibility (as deter-
mined by increased knee-extension range of motion)
revealed that following 1-session of static stretching
the increase of 4% lasted only 3 minutes after cessa-
tion of the stretching protocol,14 whereas following 1-
session of hold-relax stretches the relative change of
7% lasted 6 minutes after the stretching protocol ended.34
Recent research has reported that a single massage of the
hamstring muscle group is not associated with any sig-
nificant increase in sit and reach test performance imme-
diately after treatment in physically active young men.2
In the present study, flexibility was measured for
no longer than 8-min after the protocol ended, there-
fore the duration of maintained flexibility was not
exactly defined, even though the maximum relative
change occurred at 6-min and significant changes were
measured after the end of treatment in both groups.
Finally, the large improvement in flexibility resulted
from the combination of the vibratory treatment and
position adopted on the vibrating plate.
CHRONIC FLEXIBILITY AND REACTIVE STRENGTH
Unexpectedly, the vibratory treatment did not pro-
duce a significant adaptive response over the 8-week
period in flexibility test (Figure 9). On the contrary, the
Vibration Group improved reactive strength (16% in
Drop Jump Power) significantly over the same period
of treatment (Figure 10).
Vibrations applied locally and conventional stretch-
ing exercises resulted in a mean increase of 8.7% in a
two-leg split exercise for flexibility after three weeks
of treatment.22 A similar long term-term study report-
ed a significant increase in forward leg splits exercis-
es that ranged from 6 to 9 cm.33 Furthermore, when 4-
weeks of whole-body vibration are combined with the
contract-release stretching method there may be an
additional positive effect of 30 % on flexibility in the
hamstring muscles.39
The disagreement between the current study and
those aforementioned is most likely due to marked
differences in experimental designs, subjects, and out-
come measures used in those studies. In particular,
the vibration load was superimposed on stretching
exercises in all of the studies, which is completely dif-
ferent from whole-body vibration being applied alone.
From a methodological point of view only the paper by
Fagnani et al. study 17 seems comparable to the present
study. Contrary to our results, they reported a signifi-
cant effect of 13% using the sit and reach test, after 8-
weeks of whole-body vibration in female competitive
athletes. However, in the latter study the subjects stood
with one leg flexed at 90° degrees on the vibrating
platform and the other leg held in the air. Therefore, the
subjects assumed a one-legged half-squat position that
clearly differs from the standard two legged half-squat
position as reported both elsewhere and in the present
study. Our impression is that the other leg “held in the
air” might have produced a positive effect similar to
stretching exercises. Another important feature in the
study of Fagnani et al.17 and in contrast to the present
study, was that the subjects in their control group did
not perform any exercise on the vibrating plate at all
but nevertheless showed a tendency to increase scores
in the sit and reach test (6-7%; not significant). In light
of these considerations a benefit derived from the com-
bination of the regular training load which these female
competitive athletes underwent and whole-body vibra-

MINERVA MEDICA
COPYRIGHT®
DI GIMINIANI EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION
150 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS June 2010
tion cannot be excluded in the vibration group. In fact,
stretching training sessions were always included in
their activities (volleyball, basketball, gymnastic, and
track and field) unless special instructions were giv-
en to the subjects during the follow-up which, however,
the authors did not report in the text.
In the present study, a potential point of concern,
although in line with others studies, was the relative-
ly small sample size (N=9). Post hoc analysis of our
data showed that we could have obtained training
effects in the order of 13% on flexibility test. It may be
argued that the present study was under-powered to
detect relatively small but functionally relevant changes
in chronic flexibility. However, the effect size (ES)
was less than 0.2, which means just a 20-30 % chance
of detecting a real difference with 100 subjects
(N=100). It is highly unlikely, therefore, that a larger
sample size would have led to a different outcome in
flexibility. In addition, the same vibration treatment
improved the power in drop jump (16%, P=0.019) sig-
nificantly and post hoc analysis of these data revealed
a moderate effect size (ES=0.6).
These results confirm a previous study 15 that used
the same procedure and vibration characteristics, in
which both jumping height (22%) and power (18%)
increased significantly during 10 seconds of continu-
ous rebound jump following 8-weeks of whole-body
vibration. In the latter, the authors argued that the
influence of individualized whole-body vibration is
most notable when movement or strength exertion is
performed with short angular displacement and when
the muscle stretch is fast; that is vertical jumps char-
acterized by a stretch-shortening cycle induced by a
brief phase of impact (drop jumps and rebound
jumps).40, 41 Moreover, since the triceps surae are the
dominant muscles in this type of vertical jump, it could
explain the greater improvement compared to the squat
jump and counter movement jump.25 In light of these
results, we can point out that reactive strength is more
sensitive to whole-body vibration than flexibility.
Conclusions
The results of the current study show that individu-
alized whole-body vibration without superimposing
other exercises produces greater short-term effects on
lower back and hamstring flexibility compared to a
control group. These findings suggest that individu-
alized whole-body vibration intervention is an appro-
priate preparatory activity for training or competition.
Since whole-body vibration failed to induce a long-
term effect on flexibility, the reduced stretch pain
seems to be the major mechanism responsible in medi-
ating the flexibility performance by enhancing acute
and residual effects of whole-body vibration. Finally,
individualized whole-body vibration intervention influ-
ences over time the reactive strength but not the flex-
ibility. Future studies should try to confirm the pre-
sent results and also determine the relative role of the
nervous system and viscoelastic properties of the mus-
cle-tendon complex, both associated with functional
changes induced by whole-body vibration.
References
1. Abercromby AFJ,Amonette WE, Layne CS, Mcfarlin BK, Hinman
MR, Paloski WH. Variation in neuromuscular responses during acute
whole-body vibration exercise. Med Sci Sports Exerc 2007;39:
1642-50.
2. Barlow A, Clarke R, Johnson N, Seabourne B, Thomas D, Gal J.
Effect of massage of the hamstring muscle group on performance of
the sit and reach test. Br J Sports Med 2004;38:349-51.
3. Bosco C, Cardinale M, Colli R, Tihanyi J, von Duvillard SP,Viru A.
The influence of whole body vibration on jumping ability. Biol Sport
1998;15:157-64.
4. Bosco C, Cardinale M, Tsarpela O. The influence of vibration on
mechanical power and electromyogram activity in human arm flex-
or muscles. Eur J Appl Physiol 1999a;79:306-311.
5. Bosco C, Colli R, Introini E, Cardinale M, Tsarpela O, Madella A et
al. Adaptive responces of human skeletal muscle to vibration exposure.
Clin Physiol 1999b;19:183-7.
6. Bosco C, Iacovelli M, Tsarpela O, Cardinale M, Bonifazi M, Tihanyi
J et al. Hormonal responces to whole body vibrations in man. Eur J
Appl Physiol 2000;81:449-54.
7. Bosco C, Komi PV. Potentiation of the mechanical behaviour of the
human skeletal muscle through prestretching. Acta Physiol Scand
1979;106:467-72.
8. Bosco C, Luhtanen P, Komi PV. A simple method for measurement of
mechanical power in jumping. Eur J Appl Physiol 1983; 50:273-82.
9. Cardinale M, Bosco C. The use of vibration as an exercise interven-
tion. Exerc Sport Sci Rev 2003;31:3-7.
10. Cochrane DG, Stannard SR. Acute whole body vibration training
increases vertical jump and flexibility performance in elite female
field hockey players. Br J Sports Med 2005;39:860-5.
11. de Ruiter CJ, Van Der Linden RM, Van Der Zijden MJ, Hollander
AP, De Haan A. Short-term effects of whole-body vibration on max-
imal voluntary isometric knee extensor force and rate of force rise. Eur
J Appl Physiol 2003a;88:472-5.
12. de Ruiter CJ, Van Rask SM, Schilperoort JV, Hollander AP, De Haan
A. The effects of 11 weeks whole body vibration training on jump
height, contractile properties and activation of human knee exten-
sors. Eur J Appl Physiol 2003b;90:595-600.
13. Delecluse C, Roelants M, Verschueren S. Strength increase after
whole-body vibration compared with resistance training. Med Sci
Sports Exerc 2003;35:1033-41.
14. DePino GM, Webright WG, Arnold BL. Duration of maintained ham-
string flexibility after cessation of an acute static stretching protocol.
J Athl Train 2000;35:56-59.
15. Di Giminiani R, Tihanyi J, Safar S, Scrimaglio R. The effects of vibra-

MINERVA MEDICA
COPYRIGHT®
Vol. 50 - No. 2 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS 151
EFFECTS OF INDIVIDUALIZED WHOLE-BODY VIBRATION DI GIMINIANI
tion on explosive and reactive strength when applying individualized
vibration frequencies. J Sports Sci 2009;27:169-77.
16. Eklund G, Hagbarth KE. Normal variability of tonic vibration reflex-
es in man. Exp Neurol 1966;16:80-92.
17. Fagnani F, Giombini A, Di Cesare A, Pigozzi F, Di Salvo V. The
effects of a whole-body vibration program on muscle performance and
flexibility in female athletes. Am J Phys Med Rehabil 2006;85:
956-62.
18. Hagbarth KE. Evaluation of and methods to change muscle tone.
Scand J Rehabil Med 1994;30:19-32.
19. Halbertsma JPK, van Bolhuis AI, Göeken LNH. Sport stretching:
effect on passive muscle stiffness of short hamstrings. Arch Phys Med
Rehabil 1996;77:688-92.
20. Holt LE, Pelham TW, Burke DG. Modifications to the standard sit-and-
reach flexibility protocol. J Athl Train 1999;34:43-7.
21. Hopkins WJ. Measures of reliability in sports medicine and science.
Sports Med 2000;30:1-15.
22. Issurin VB, Liebermann DG, Tenenbaum G. Effect of vibratory stim-
ulation training on maximal force and flexibility. J Sports Sci
1994;12:561-6.
23. Jacobs PL, Burns P. Acute enhancement of lower-extremity dynam-
ic strength and flexibility with whole-body vibration. J Strength Cond
Res 2009;23:51-7.
24. Johnston RM, Bishop B, Coffey GH. Mechanical vibration of skele-
tal muscles. Phys Ther 1970;50:499-505.
25. Kovács I, Tihanyi J, DeVita P, Rácz L, Barrier J, Hortobágyi T.
Kinemetic and kinetic comparison of heel-toe and forefoot landing drop
jumps. Med Sci Sports Exerc 1999;7:708-16.
26. Lundeberg T, Nordemar R, Ottoson D. Pain alleviation by vibratory
stimulation. Pain 1984;20:25-44.
27. Luo J, McNamara B, Moran K. The use of vibration training to enhance
muscle strength and power. Sports Med 2005;35:23-41.
28. Magnusson SP,Aagaard P, Larsson B, Kjaer M. Passive energy absorp-
tion by human muscle-tendon unit is unaffected by increase in intra-
muscular temperature. J Appl Physiol 2000;88:1215-20.
29. McHugh MP, Jan JK, Fox MB, Gleim GW. The role of mechanical and
neural restraints to joint range of motion during passive stretch. Med
Sci Sports Exerc 1998;30:928-32.
30. Rittweger J, Mutschelknauss M, Felsenberg D. Acute changes in neu-
romuscular excitability after exhaustive whole body vibration exercise
as compared to exhaustion by squatting exercise. Clin Physiol Function
Imag 2003;23:81-6.
31. Roelants M, Delecluse C, Goris M, Verschueren S. Effects of 24
weeks of whole body vibration training on body composition and
muscle strength in untrained females. Int J Sports Med 2004a;25:
1-5.
32. Roelants M, Delecluse C, Verschueren S. Whole-Body-Vibration
Training Increases Knee-Extension Strength and Speed of Movement
in Older Women. J Am Ger Soc 2004b;52:901-8.
33. Sands WA, McNeal JR, Stone MH, Russell EM, Jemni M. Flexibility
enhancement with vibration: acute and long-term. Med Sci Sports
Exerc 2006;38:720-5.
34. Spernoga SG, Uhl TL, Arnold BL, Gansneder BM. Duration of main-
tained hamstring flexibility after one-time, modified hold-relax stretch-
ing protocol. J Athl Train 2001;36:44-8.
35. Torvinen S, Kannu P, Sievanen H, Jarvinen TA, Pasanen M,
Kontulainen S et al. Effect of a vibration exposure on muscular per-
formance and body balance. Clin Physiol Funct Imag 2002b;22:
145-52.
36. Torvinen S, Kannus P, Sievanen H, Jarvinen TAH, Pasanen M,
Kontulainen S et al. Effect of four month vertical whole body vibra-
tion on performance and balance. Med Sci Sports Exerc 2002c;
34:1523-8.
37. Torvinen S, Kannus P, Sievanen H, Jarvinen TAH, Pasanen M,
Kontulainen S et al. Effect of 8-months vertical whole body vibration
on bone, muscle performance and body balance: a randomized con-
trolled study. J Bone Min Res 2003;18:876-84.
38. Torvinen S, Sievanen H, Jarvinen TA, Pasanen M, Kontulainen S,
Kannus P. Effect of 4-min vertical whole body vibration on muscle per-
formance and body balance : a randomized cross-over study. Int J
Sports Med 2002a;23:374-9.
39. van den Tillaar R. Will whole-body vibration training help increase the
range of motion of the hamstrings? J Strength Cond Res 2006; abstract
20:192-6.
40. Young WB, Wilson GJ, Byrne C. A comparison of drop jump train-
ing methods: effects on leg extensor strength qualities and jumping per-
formance. Int J Sports Med 1999a;20:295-303.
41. Young WB, Wilson GJ, Byrne C. Relationship between strength qual-
ities and performance in standing and run-up vertical jumps. J Sports
Med Phys Fitness 1999b;39:285-93.