INVITED REVIEW
Vibration as an exercise modality: how it may work,
and what its potential might be
Jo
¨
rn Rittweger
Accepted: 13 November 2009 / Published online: 12 December 2009
Ó Springer-Verlag 2009
Abstract Whilst exposure to vibration is traditionally
regarded as perilous, recent research has focussed on
potential benefits. Here, the physical principles of forced
oscillations are discussed in relation to vibration as an
exercise modality. Acute physiological responses to iso-
lated tendon and muscle vibration and to whole body
vibration exercise are reviewed, as well as the training
effects upon the musculature, bone mineral density and
posture. Possible applications in sports and medicine are
discussed. Evidence suggests that acute vibration exercise
seems to elicit a specific warm-up effect, and that vibration
training seems to improve muscle power, although the
potential benefits over traditional forms of resistive exer-
cise are still unclear. Vibration training also seems to
improve balance in sub-populations prone to fall, such as
frail elderly people. Moreover, literature suggests that
vibration is beneficial to reduce chronic lower back pain
and other types of pain. Other future indications are
perceivable.
Keywords Mechanical oscillation Training
Rehabilitation Physical medicine Safety ISO standard
Nomenclature
a Acceleration, m s
-2
a
Peak
Peak acceleration, i.e. largest acceleration within
one vibration cycle. For sinusoidal oscillations
given by x
2
A (Eq. 1), m s
-2
a
RMS
Mean acceleration, i.e. average acceleration over an
entire vibration cycle. For sinusoidal oscillations
given by a
Peak
/H2 (Eq. 2), m s
-2
A Amplitude of the oscillation. In other words, the
displacement of the oscillating actuator is between
-A and A,m
BMD Bone mineral density
D Damping factor, given by the ratio of the
attenuation coefficient and x
0
EMG Electromyography
f Frequency of the oscillation, i.e. the number of
vibratory cycles per unit time. Therefore, 1/f gives
the duration of a single cycle, Hz, which is
equivalent to s
-1
g Gravitational acceleration on Earth, 9.81 m s
-2
k Stiffness, i.e. the resistance to deformation, N/m
m Mass that is inert to acceleration as well as being
accelerated by gravity, kg
p 3.1415
x Angular frequency. x is proportional to f, as it is
given by 2pf, Hz, which is equivalent to s
-1
x
0
Resonance frequency of the resonator, i.e.
frequency at which mechanical energy will
be accumulated, expressed as angular frequency,
Hz
x
A
Angular frequency of the actuator, Hz
Communicated by Susan Ward.
J. Rittweger (&)
Institute of Aerospace Medicine,
German Aerospace Center,
Linder Ho
¨
he 1, Ko
¨
ln 51147, Germany
e-mail: joern.rittweger@dlr.de
J. Rittweger
Institute for Biomedical Research into Human Movement
and Health (IRM), Manchester Metropolitan University,
Oxford Rd, Manchester M1 5GD, UK
123
Eur J Appl Physiol (2010) 108:877–904
DOI 10.1007/s00421-009-1303-3
Introduction
A visit at the local gym will demonstrate how popular
vibration exercise currently is, with numerous devices
available for exercise and physical therapy. However, the
notion that vibration can be beneficial is relatively new, as
it has traditionally been regarded as only detrimental. That
view originated from occupational exposure to vibration. In
the neuronal sciences, by contrast, vibration is a standard
tool of investigation (Hagbarth and Eklund 1969). It is
therefore fair to say that studies of vibration effects have a
long tradition.
Nevertheless, only few authors have postulated thera-
peutic effects by vibratory stimuli in the past. Among them,
the first were Sanders (1936) and Whedon et al. (1949),
who performed some studies on an oscillating bed, meant
to counteract cardiovascular and musculoskeletal de-con-
ditioning. Nazarov and Spivak (1985) were the first to
apply vibration as a training modality for athletes. With
some delay, this led to an emerging scientific interest in
vibration as an exercise modality (Bosco et al. 1998a, b,
1999a, b, 2000; Issurin and Tenenbaum 1999; Kerschan-
Schindl et al. 2001; Rittweger et al. 2000, 2002a), not least
driven by companies who started to market commercial
devices.
However, vibration exercise nowadays being broadly
available to exercisers and patients, it seems that this
exercise modality is still largely unknown to the scientific
community, and there is currently no comprehensive
review available on the topic to allow an in-depth under-
standing, which is the purpose of the current article. Two
fascinating fields, however, will go more or less unmen-
tioned, namely central nervous information processing of
vibration, as it is too complex to be covered here, and the
potential effects upon adipogenesis, for which the available
evidence is still preliminary.
When being vibrated on a platform, most people report
an unusual perception that is often compared to the ranging
and banging of the feet during downhill skiing. This sen-
sation is partly due to a movement illusion (see ‘‘Neuro-
physiological responses’’), and there is also a perception of
exertion, which is not explicable by metabolic rate (see
Fig. 1). Vibration applied to the tendons during isometric
contractions leads to an over-estimation of the force gen-
erated by 30% (Cafarelli and Kostka 1981), and, con-
versely, a 25% smaller than intended force is generated.
Quite confusingly, the discrepancy between intended and
actual force levels declines during prolonged contractions
(Cafarelli and Layton-Wood 1986). The important question
therefore is whether the current interest in vibration as an
exercise modality is only due to unduly perceived exertion,
or whether it can really constitute a physiological training
stimulus.
Physical principles
Vibration is a mechanical oscillation, i.e. a periodic alter-
ation of force, acceleration and displacement over time.
Vibration exercise, in a physical sense, is a forced oscilla-
tion, where energy is transferred from an actuator (i.e. the
vibration device) to a resonator (i.e. the human body, or
parts of it). In most vibration exercise devices, these
oscillations have sinusoidal shape, and they are therefore
described by amplitude A, frequency f, and phase angle u.
Here and in the following A denotes the mathematical
amplitude, i.e. half the peak-to-peak amplitude. The angular
frequency x is given as 2pf. During vibration exercise, the
human body is accelerated, which causes a reactive force by
and within the human body. Importantly, the peak accel-
eration (a
Peak
) in sinusoidal oscillation is given by
a
Peak
¼ x
2
A: ð1Þ
Peak forces are potentially harmful to the body. On the
other hand, forces also constitute a training stimulus.
Therefore, a
Peak
values are important to consider. Another
convention to quantify vibration exposure is by RMS
(meaning root-mean square), which for sinusoidal
oscillations relates to a
Peak
as
a
RMS
¼
a
Peak
ffiffiffi
2
p
: ð2Þ
Fig. 1 Rating of perceived exertion (RPE) on a scale of 20 (Borg and
Borg 1976) during either simple squatting exercise (ordinate) or whole
body vibration exercise (abscissa) on a Galileo Fitness platform
(Novotec Medical, Pforzheim, Germany). Both conditions were set up
so that the metabolic rates were matched (squatting: 11.4 ml
O
2
kg
-1
min
-1
(SD 0.7), vibration 10.7 ml O
2
kg
-1
min
-1
(SD 1.0),
p = 0.3). By contrast, RPE was significantly greater in vibration (mean
11.9, SD 2.4, dashed line) than in squatting (mean 9.3, SD 2.1, solid
line) exercise, suggesting that at perceived exertion is at least partly
dominated by factors unrelated to metabolic rate. Interestingly, there
seems to be no relationship between RPE values for vibration and
squatting conditions, indicating that different people perceive both
exercise modalities as differently exerting. Data are from an unpub-
lished experiment by Rittweger & Degens
878 Eur J Appl Physiol (2010) 108:877–904
123
The actuator: different device types
Vibration exercise is mostly practiced as whole body
vibration, i.e. while standing on oscillating platforms.
Among the different platforms, two different types of
energy transfer have to be discerned. One type transfers
vibration to both feet synchronously, whilst the second type
operates in a side-alternating way, so that the right foot is
lowest when the left foot is highest (and vice versa,
Fig. 2a). It has been argued that side-alternating vibration
would evoke rotational movements around the hip and
lumbo-sacral joints (Rittweger et al. 2001). This movement
introduces an additional degree of freedom (see next sec-
tion) and, accordingly, whole-body mechanical impedance
is smaller in side-alternating than in synchronous whole
body vibration (Abercromby et al. 2007b). It should be
mentioned here that attempts have been made to develop a
third device type with randomly varying movements in the
horizontal and vertical plane. However, there are only very
few studies on this random vibration system, and due to
technical difficulties only vibration frequencies well below
10 Hz have been tested so far.
Finally, vibrating dumbbells have been developed for
upper-body exercise, which can be suspended and com-
bined with weight stacks (Cardinale and Rittweger 2006).
Their mechanical action on the human body will depend on
the specific set-up. However, when controlling for the
effective stimulatory parameters (force, velocity, energy),
the physiological responses to these devices should
resemble the response to platform devices.
Devices also differ by way of energy generation. Whilst
some operate by direct mechanical transmission (e.g.
Galileo
Ò
), some rely upon electromagnetic transmission,
and most available machines are based on oscillating mass-
spring systems (e.g. PowerPlate
Ò
or FitVibe
Ò
). As one
would expect, not all systems perform equally well (see
http://www.massamagra.com/pedane-vibranti/
recensioni.htm), and scientists should convince themselves,
e.g. by using accelerometers, of an accurate setting.
The resonator: importance of stiffness, damping
and posture
What happens to the body when being vibrated? As a first
approximation, consider a rigid body with mass m. When
the attachment of such a rigid body to the vibration device
is firm, then it will simply follow the sinusoidal trajectory
imposed by the actuator. The force applied is then deter-
mined by the acceleration of m. On whole-body platforms,
however, there is no firm attachment and the only down-
ward force acting on the body is gravity (Yue and Mester
2002). As a consequence, the rigid body will lose contact
and become air-bound when the acceleration of the plat-
form is smaller than -1g (see Fig. 3). Practically, this is
the reason why people’s feet sometimes skid on the
vibration plate. Moreover, as can also be seen from Fig. 3,
a collision with the platform will occur towards the end of
the air borne phase. This leads to the generation of impact
forces. Spectral analysis will interpret such impacts as
frequencies greater than the vibration frequency, some of
which will impose as harmonics (i.e. spectral power at 2f,
3f,4f etc.). Conversely, being air-bound can also lead to
missing out one or several cycles of the vibration platform,
and thus generate sub-harmonic frequencies (i.e. f/2, f/3,
f/4) in the vibrated object. Hence, firm stance on the force
plate must be achieved in order to ascertain well-defined
vibration parameters.
Obviously, however, the human body is not a rigid body,
and muscles and tendons act as spring-like elements that
store and release mechanical energy. In such a spring-mass
system, compression occurs during the vibration upstroke,
and expansion during the down stroke. As a consequence,
the displacement is smaller at the body’s centre of mass
than at the platform level. Together, the stiffness and mass
determine the natural frequency (x
0
) of such a system.
More precisely, x
0
¼
ffiffiffiffiffiffiffiffiffi
k=m
p
; where k is stiffness and m
mass. Obviously, adjustment of x
0
must be through alter-
ation of k,asm cannot be changed.
It is important to understand that such a mass-spring
resonator can accumulate mechanical energy, namely when
Synchronous Side-Alternatin
g
Vibration Transmission
Fig. 2 Illustration of the two principle modes of vibration transmis-
sion in whole body vibration exercise. In the synchronous mode, both
legs extend and stretch at the same time, and a purely linear
acceleration is directed to the trunk. In the side-alternating mode,
conversely, the right and left leg operate anti-phase, which introduces
a rotary component to the lumbar spine and therefore is expected to
reduce vibration transmission to the trunk. Evidence suggests, that
greater a
Peak
levels can be tolerated in the side-alternating as opposed
to the synchronous vibration mode (Abercromby et al. 2007b)
Eur J Appl Physiol (2010) 108:877–904 879
123
the frequency of the actuator, x
A
, matches the frequency of
the resonator, x
0
. The accumulation of energy can lead to a
situation where the vibration amplitude is greater in the
resonator than in the actuator. This amplitude amplification
entails increased internal forces within the resonator, which
can lead to its destruction—the so-called resonance catas-
trophe. It is crucial to bear in mind that amplitude ampli-
fication can only occur if there is little damping (see
Fig. 4a). Moreover, not all amplitude amplification causes
resonance catastrophe, as this will happen only if the
generated forces exceed the resonator’s structural strength.
Nevertheless, resonance should be prevented in vibration
exercise, e.g. by alteration of stiffness and thus x
0
,orby
introducing a damping element (friction). Evidence sug-
gests that muscles have such damping properties (Wake-
ling et al. 2002). However, any mechanical damping will
lead to the absorption of energy and thus generate heat.
Finally, considering to the human anatomy, we have to
consider the way in which vibrations are transmitted. This
will occur from one segment to the next, i.e. from the foot
to the calf, from the calf to the thigh etc. The amount of
vibration energy transmitted will depend on musculoskel-
etal stiffness and damping (see subsection Vibration
transmission at the end of this article for specific details).
Importantly, effective axial body stiffness increases with
straightened limbs (Greene and McMahon 1979; Lafortune
et al. 1996), which also leads to an increase in resonance
frequency. Assuming an appropriate posture can therefore
help to avoid resonance. Equally important, standing on the
forefoot will involve the ankle joint actuators (i.e. the calf
muscles) in the damping process, which is not the case
when stance is on the mid-foot (see Fig. 4b). Posing weight
on the forefoot, therefore, can help to avoid resonance, and
also to increase damping by the musculature and thus
reduce vibration transmission to the trunk. Hence, assum-
ing an appropriate posture is the prerequisite to avoid
unpleasant head and trunk vibration, and also to provide
firm stance on the vibrating platform.
Acute physiological effects
Muscle and tendon mechanics
What happens to the muscle–tendon complex during
vibration exercise? Given that a
Peak
levels at the head
are usually much smaller than at the vibrating platform
(Abercromby et al. 2007b), one has to assume that muscles
and tendons will elongate at one time (stretch phase), to be
followed by a period of shortening (shortening phase). In
other words, vibration exercise should be characterized by
cyclic transition between eccentric and concentric muscle
contractions. A recent study suggests that this is indeed the
case, and that the gastrocnemius muscle tendon complex is
Fig. 3 Demonstration of the
behaviour of a rigid body that is
attached to a vibration platform
by gravity only. The upper
diagram shows the
displacements of the platform
and the rigid body, respectively.
In this example, where
f = 15 Hz, A = 2 mm and
a
Peak
= 1.81 g, the rigid body
will be lifted off the platform
just before the platform reaches
its highest position, and the
rigid body hits the platform just
after it reaches its lowest
position. This causes a distinct
impact, as demonstrated by the
acceleration depicted in the
lower diagram. It is obvious,
however, that the human body is
not completely rigid, but rather
has elastic and damping
properties. Nevertheless, the
feet can sometimes be lifted off
the platform during whole body
vibration exercise, which leads
to a loss of contact and skidding
880 Eur J Appl Physiol (2010) 108:877–904
123
elongated by 1% of its total length during 6 Hz vibration
cycles with a
Peak
= 0.6g (Cochrane et al. 2009).
Neurophysiological responses
Although no study has yet assessed the motor unit dis-
charge patterns during vibration exercise, the neurophysi-
ological responses of the muscle to isolated vibrations
applied are very well studied. Applying vibration directly
to the muscle belly or tendon elicits a phase-oriented dis-
charge from primary (Brown et al. 1967; Burke et al. 1976;
Homma et al. 1971; McGrath and Matthews 1973; Roll and
Vedel 1982) and also secondary spindle endings (Brown
et al. 1967; Burke et al. 1976; McGrath and Matthews
1973). Between the two, primary endings are more
responsive than secondary endings (Bianconi and van der
1963; Brown et al. 1967). The spindle discharge depends
on the pre-stretch of the muscle and generally increases
with muscle length or stretch (Burke et al. 1976; Cordo
et al. 1993). It is also enhanced during voluntary isometric
contraction (Burke et al. 1976). In addition to the spindle
afferents, Ib-afferents from Golgi tendon organs are like-
wise responsive to muscle vibration (Burke et al. 1976;
Hayward et al. 1986). Like the spindle endings, afferents
from Golgi tendon organs become more responsive to
vibration when the muscle is contracting (Brown et al.
1967). The Golgi organ is believed to measure tendon
elongation, and thus a surrogate of force. It elicits an
inhibitory effect upon motor output via polysynaptic spinal
pathways, and its information converges with that from
cutaneous receptors, spindle afferents, joint receptors and
others (Lundberg et al. 1975).
Importantly, spindle discharge will elicit an excitatory
effect upon the a-motoneurone, either by monosynaptic
(primary or Ia afferents) or polysynaptic (secondary or
II-afferents) pathways and thus foster contractions of the
homonymous muscle (Granit et al. 1956). Passive muscle
vibration therefore causes a reflex contraction, also known
as the tonic vibration reflex (Hagbarth and Eklund 1966;
Matthews 1966). It is characterized by a gradual onset, and
it can be voluntarily suppressed (Hagbarth and Desmedt
1973; Lance et al. 1973). Alongside the contraction, people
experience an illusion of movement during the tonic
vibration reflex (Goodwin et al. 1972a, b). During the
reflex contraction, the discharge from both primary and
secondary spindle endings seem to decline, whereas the
discharge from Golgi tendon organs is increased (Burke
et al. 1976). Microneurographic evidence in humans
suggests that the reflex contraction crucially depends on
fusimotor efferents (Burke et al. 1976), suggesting that
supra-spinal control is involved in it. In relation to this, it
has been pointed out that the reflex contraction bears
similarities with Kohnstamm’s phenomenon (Bergenheim
et al. 2000; Gilhodes et al. 1992
).
m
body
thigh
calf
foot
F
F’
(a) (b)
Fig. 4 Model of the human body as a resonator, composed of a single
(a) or multiple (b) segments with spring-like and damping behaviour.
a A mass is linked to a spring with stiffness k and a dashpot with
friction b (see inset). This system can act as a resonator with
resonance frequency -
0
. When driven by an actuator with angular
frequency -
A
, transmissibility is determined by -
A
/-
0
(=normalized
frequency) and the grade of damping D. Amplitude amplification is
defined by transmissibility [1, i.e. when the amplitude of the
resonator is larger than the amplitude of the actuator. This occurs
when D is below a critical value and when -
0
& -
A
. Adapted from
Hering et al. (2004). b The calf and thigh muscles are idealized as
spring-dashpot systems, which can store and absorb energy. Force F
applies at the foot and thus loads the calf muscles and potentially also
the thigh muscles. By contrast, force F’ applies at the rotational centre
of the ankle and will therefore load the thigh muscles, but not the calf
muscles. Posing weight on the forefoot or on the mid-foot can thus
alter the transmission of vibration and thus relative loading of calf and
thigh muscles in whole body vibration exercise. Conversely, locking
of the knees will reduce energy absorption in the thigh muscles and
lead to greater vibration transmission to the trunk. It should be
understood that this model is an over-simplification. However, it
constitutes a basis for understanding the physics of whole body
vibration. Several mechanical models have been developed that
provide more detail than the simple sketch in this figure (Cole 1978;
Ghista 1982; Yue and Mester 2002). They indicate that amplitude
amplification may occur under certain circumstances, and it is
therefore important to assess vibration transmission by physical
measurements (see also ‘‘Vibration transmission’’ )
Eur J Appl Physiol (2010) 108:877–904 881
123
