JOURNAL OF BONE AND MINERAL RESEARCH

Volume 19, Number 8, 2004

Published online on April 5, 2004; doi: 10.1359/JBMR.0315011
© 2004 American Society for Bone and Mineral Research

Editorial
Whole Lotta Shakin’ Goin’ On

Olof Johnell1 and John Eisman2

INTRODUCTION SHAKINⴕ ALL OVER

HAKE, RATTLE, AND roll have now entered the osteopo- In humans, extremely low-level, high-frequency mechan-
S rosis quietness with two papers on the clinical effect of
whole body vibration in the March issue of JBMR. Besides,
ical accelerations have been shown to be readily transmitted
into the lower appendicular and axial skeleton of the stand-
we can already see these products at scientific meetings. To ing individual.(6) In a recent study, 21 male and 35 female
what extent does the present knowledge address the poten- volunteers (age, 19 –38 years) were randomly assigned to a
tial for such approaches in the prevention of fractures? vibration or control group. Individuals stood on a vibration
platform that was either stationery or oscillated in an as-
GOOD VIBRATIONS cending order from 25 to 45 Hz, corresponding to maximum
Clinical studies have been based on animal experiments vertical accelerations from 2g to 8g, for 4 minutes/day, 3–5
that have shown a positive effect on bone strength and mass times/week, over an 8-month period.(7) Although there was
of various forms of loading. The basis of these experiments no effect on bone mass, serum markers, or other perfor-
is the concept that trabecular bone adapts to its mechanical mance and balance tests, there was an increase in vertical
environment—Wolff’s law. Support for these experiments jump height in the vibration group.
has also come from epidemiological findings that greater In this issue, Verschueren et al.(8) report on a 6-month
physical activity–mechanical stimulation is associated with study of whole body vibration in older women with respect
greater bone mass, and in some studies, fewer fractures. to hip density, muscle strength, and postural control. The 70
The question of the ideal form of stimulation has been volunteer women, 60 –70 years of age, who were healthy
addressed in animal studies. High-frequency (30 Hz), low- and had a BMD T score ⬎ ⫺2, were randomized to a
magnitude (200 ␮strain) signals stimulated large increases control group with no organized training; resistance training
in cortical bone in turkeys.(1–3) However, higher amplitude knee extensor by dynamic leg press and leg extension
and lower frequency was not anabolic in that model. In a exercises or whole body vibration, where the subjects per-
longer-term study in sheep over 1 year, daily 20-minute formed the same exercises for 20 minutes/day on a vibration
sessions of high-frequency mechanical stimulation of sheep platform that had a vibration frequency of 35– 40 Hz and
produced a 35% increase in BMD. This kind of vibration peak acceleration of 2.3–5.1g. The vibration training im-
may also affect the sarcopenia that occurs at the same time proved the isometric and dynamic muscle strength by 15%
as bone loss with aging. Other animal studies have shown and 16%, respectively, and increased BMD by 0.93%. No
similar results. Low-magnitude mechanical loading became hip BMD change was observed in the resistance training or
osteogenic when rest is inserted between each load cycle.(4) the age-matched controls. Serum markers of bone turnover
Effects of loading frequency on mechanically induced bone did not change in any groups. The authors concluded that
formation and periosteal osteogenesis suggested a complex whole body vibration training might be a feasible and ef-
interaction between extracellular fluid forces and cellular fective way to modify well-recognized risk factors for falls
mechanics in mechanotransduction, best predicted by a and fractures in elderly women.
mathematical model that assumed that (1) bone cells are Also in this issue, Rubin et al.(9) report another trial for 1
activated by fluid shear stresses and (2) stiffness of the bone year in 70 healthy women who were 3– 8 years postmeno-
cells and the extracellular matrix near the cells increases at pausal (mean age, 57 years). Those randomized to the
higher loading frequencies because of viscoelasticity.(5) vibration platform were exposed to a peak vertebral accel-
These animal experiments have formed the scientific basis eration of 0.2g at a frequency of 30 Hz. Compliance was not
for studies in humans. good as in many other exercise (and pharmacologic) inter-
ventions, and the intention-to-treat analysis did not show an
The authors have no conflict of interest. effect. In an analysis limited to those in the highest quartile

1
Department of Orthopaedics, Malmö University Hospital, Lund University, Malmö, Sweden; 2Garvan Institute of Medical Research,
University of New South Wales, St Vincent⬘s Hospital, Sydney, Australia.

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1206 JOHNELL AND EISMAN

of compliance (86% compliant), vibration subjects gained what similar benefit, provided that good compliance can be
0.04% in femoral neck BMD, whereas placebo subjects lost achieved. However, it is recognized that change in BMD
2.13% over 1 year in the femoral neck. The corresponding cannot be easily translated to fracture reduction. Thus, the
figures for the lumbar spine were ⫹0.1% and ⫺1.6%. burning question is what fracture reduction could be
Interestingly, the lower body weight (⬍65 kg) women ex- achieved with whole body vibration.
perienced the greatest benefit: a 3.4% increase in the highest
compliance group and a 2.7% increase in the mean compli- Future
ance group. The authors concluded that these preliminary A tantalizing possibility is that there could be an interac-
results indicate a potential for a noninvasive mechanical tion between whole body vibration and pharmacologic treat-
mediated intervention for osteoporosis that is perhaps more ment. Could whole body vibration enhance the effect of an
effective in lighter women, who are at greatest need of anabolic agent or an antiresorptive? In one study in rat tail,
intervention. there was a synergistic effect of parathyroid hormone (PTH)
How shall interpret these trials? First, there are differ- and mechanical stimulation on trabecular bone forma-
ences in age. The study by Torvinen et al.(7) had younger tion.(16) It remains to be seen whether similar interactions
and perhaps more healthy participants. The greater benefit could be seen in humans, where no major effect on bone
in lighter individuals in the Rubin study could explain some turnover from whole body vibration has been observed. A
of these differences. Although there were differences in further development in the future might be shock wave
study duration, these overlapped and do not seem to explain treatment, which in animals, has been shown to be positive
any of the differences reported. The Torvinen study used a with increased bone mass in fractured limbs.(17)
short exposure period (4 minutes) for each treatment and
somewhat greater loads, although at similar frequency.(7) WHAT’S SHAKINⴕ?
None of the studies showed any differences in bone turn-
over markers, but there were observable differences in mus- What are the requirements to bring this equipment to the
cle strength (e.g., jump height). These possibilities require market place? Vibration platforms are regarded as “devices”
examination in further studies with respect to study sample and not a pharmaceutical intervention; therefore, they are
age and weight, as well as vibration exposure and ampli- subject to different regulatory criteria for safety and effi-
tude. cacy. Therefore, for considerations of clinical application, it
is important to determine what kinds of data are needed to
Any side effects?
support vibration as a valid and rational treatment option.
Vibration of the human body has been proposed from Should BMD change be sufficient or should we require
epidemiological studies to cause back pain. However, no fracture reduction data ? Is analysis by compliance reason-
such major side effects were reported from these studies, able in light of our judgments about other randomized
and whole body vibration exercise has been proposed for placebo controlled trials, where intention to treat (ITT) is
treatment of chronic low back pain.(10) Another possible and should remain the gold standard? Although vibration
safety aspect is that the displacement could be large enough platforms seem to be relatively safe, it will be important to
for the patient to fall, but this was not reported in these establish their antifracture and BMD efficacy as well as
studies. their safety in larger and more adequately powered random-
ized double-blinded controlled trials.
What could be the biological mechanisms of this whole
body vibration? REFERENCES
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Address reprint requests to:
ing potentials measurements. Ann Biomed Eng 30:693–702. Olof Johnell, MD
12. Rubin C, Turner AS, Mallinckrodt C, Jerome C, McLeod K, Bain Department of Orthopaedics
S 2002 Mechanical strain, induced noninvasively in the high- Malmö University Hospital
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