High-Frequency Vibration Training Increases Muscle Power in
Postmenopausal Women

Cosimo Roberto Russo, MD, Fulvio Lauretani, MD, Stefania Bandinelli, MD, Benedetta Bartali, MD,
Chiara Cavazzini, MD, Jack M. Guralnik, MD, PhD, Luigi Ferrucci, MD, PhD

ABSTRACT. Russo CR, Lauretani F, Bandinelli S, Bartali age. Although evidence is overwhelming that physical exercise B, Cavazzini C, Guralnik JM, Ferrucci L. High-frequency positively affects muscle strength at all ages, compliance of vibration training increases muscle power in postmenopausal older persons with traditional exercise programs has generally women. Arch Phys Med Rehabil 2003;84:1854-7.
been low, and only a small percentage of older persons exerciseregularly.3 Objective: To test whether training on a high-frequency
Vibration exercise on ground-based platforms that oscillate (28Hz) vibrating platform improves muscle power and bone at high frequency has recently been proposed as an intervention characteristics in postmenopausal women.
for the prevention and the treatment of osteoporosis.4-6 High- Design: Randomized controlled trial with 6-month follow-
frequency (28Hz), very-low-magnitude (0.3g) vibration exer- cise has recently been reported to increase bone mass in ex- Setting: Outpatient clinic in a general hospital in Italy.
Participants: Twenty-nine postmenopausal women (inter-
mechanism by which vibrations influence the bone tissue re- vention group, nϭ14; matched controls, nϭ15).
Intervention: Participants stood on a ground-based oscillat-
The high-frequency postural displacements induced by the ing platform for three 2-minute sessions for a total of 6 minutes alternating movements of the platform produce reflex muscle per training session, twice weekly for 6 months. The controls contractions aimed at stabilizing posture.11 Thus, vibration can did not receive any training. Both groups were evaluated at be viewed as a special form of muscle training that may particularly affect muscle power.12 It has been proposed that Main Outcome Measure: Muscle power, calculated from
the force applied to bone during muscle contraction has a ground reaction forces produced by landing after jumping as pivotal role in the homeostatic and adaptive regulation of bone high as possible on a forceplate, cortical bone density, and strength.13,14 This hypothesis may explain, in part, the mecha- nism by which vibration improves bone strength. To test this Results: Over 6 months, muscle power improved by about
hypothesis, we conducted a small, randomized controlled trial 5% in women who received the intervention, and it remained (RCT) to discover whether training on a high-frequency vibrat- unchanged in controls (Pϭ.004). Muscle force remained stable ing board for 6 months would improve muscle power in post- in both the intervention and control groups. No significant menopausal women and, in turn, positively influence bone changes were observed in bone characteristics.
Conclusion: Reflex muscular contractions induced by vibra-
tion training improve muscle power in postmenopausal Key Words: Bone density; Exercise; Muscles; Postmeno-
pause; Rehabilitation; Vibration; Women.
2003 by the American Congress of Rehabilitation Medi- All the study procedures, including recruitment, measure- cine and the American Academy of Physical Medicine and ments, and intervention, were performed in the Nuovo San Giovanni di Dio Hospital in Florence, Italy. The recruitmentphase began in spring 1999 and was completed in fall 1999.
MUSCLE POWER, the capacity of muscles to produce The intervention began in the winter 1999–2000 and was
work in the environment, declines significantly over the completed by summer 2000. Among the 67 women belonging life span. In women, the rate of decline accelerates after meno- to a hospital volunteers association (Associazione Volontari pause and leads to reduction in physical functioning.1 It has Ospedalieri), 39 women who were at least 1 year postmeno- been hypothesized that this process may be responsible for the pausal and not affected by conditions that contraindicated the development of physical frailty and mobility disability1,2 in old vibration training were enrolled in the study population (fig 1).
Women on hormone replacement therapy were consideredeligible. Women with metabolic bone disorders were excludedfrom the trial.
From the Laboratory of Clinical Epidemiology, INRCA Geriatric Department, The screened women entered a 3-month run-in phase during Florence, Italy (Russo, Lauretani, Bandinelli, Bartali, Cavazzini); Laboratory of which they received daily 1g of calcium carbonate and .25␮g Epidemiology, Demography, and Biometry, National Institute on Aging, Bethesda, of activated vitamin D (calcitriol). This supplementation was MD (Guralnik); and Longitudinal Studies Section, ASTRA Unit, Clinical ResearchBranch, National Institute on Aging, Baltimore, MD (Ferrucci).
administered to all the participants for the entire study period to Stratec Medizintechnik, Novotec, and Unitrem provided the peripheral quantitative avoid any influence of insufficient calcium or vitamin D intake computerized tomograph and the forceplates.
on the effects of vibration exercise on bone apposition and No commercial party having a direct financial interest in the results of the research mineralization. Because of the nature of the intervention, no supporting this article has or will confer a benefit upon the author(s) or upon anyorganization with which the author(s) is/are associated.
blinding or placebo was considered. Of the 67 screened Reprint requests to Luigi Ferrucci, MD, PhD, Longitudinal Studies Section, Clin- women, 33 agreed to participate in the study, signed an in- ical Research Branch, Gerontology Research Center, National Institute on Aging, formed consent, and were randomized to either vibration or 5600 Nathan Shock Dr, Rm 6BN, Baltimore, MD 21224.
control group. A simple randomization procedure was applied 0003-9993/03/8412-7841$30.00/0doi:10.1016/S0003-9993(03)00357-5 using a series of random numbers. Six of the 39 eligible women Arch Phys Med Rehabil Vol 84, December 2003
cross-sectional image of the tibial diaphysis at 38% of the tibiallength from its distal end. In these images, all of the voxelswith a density above 710mg/cm3 were considered to belong tocortical bone.
The active intervention consisted of brief training sessions conducted twice weekly for 6 months. In each session, vibra-tion was provided by a commercially available device (Galileo2000d). By means of an oscillating board, this device delivershigh-frequency vibration through the legs to the whole body.
Participants stood with feet side by side on the board, whichproduced lateral oscillations of the whole body with accelera-tions in the range of 0.1 to 10g. At the beginning of thetraining, participants stood on the board with the knees slightlyflexed and received three 1-minute bouts of vibration separatedby 1-minute resting periods. During the first month of treat-ment, the frequency of vibration was progressively increasedfrom 12 to 28Hz to allow for gentle adaptation. During thefollowing 5 months of treatment, the frequency was always setat 28Hz, and the bouts of vibration were prolonged to 2 Fig 1. Flow diagram of the RCT.
minutes. Participants were invited to separate the feet as far astolerated to increase the amplitude and speed of the verticaldisplacement. Previous studies11 have demonstrated that theoscillating movement of the board produces muscle stretching, refused to participate in the trial owing to family problems which elicits alternating reflex contraction of the flexor and extensor leg muscle groups. Participants in the active group Measurements
attended on average 34 sessions, corresponding to about 200minutes of treatment, out of 44 sessions potentially available.
Blood and urine tests were performed to exclude from the trial subjects affected by metabolic bone disorders like primary Statistical Analysis
hyperparathyroidism or hyperparathyroidism secondary to re-nal failure. All blood samples were drawn in the morning All analyses were performed using the SAS, version 8.2, statistical software.e Data are reported as mean Ϯ standard chemical parameters, which included total serum calcium, se- error (SE). Baseline characteristics of the intervention and rum phosphorus, and creatinine, were measured using standard control group were compared by 1-way analysis of variance laboratory methods. Serum parathyroid hormone (PTH) was (ANOVA). The magnitude of change over time in muscle and measured by a double-antibody chemoluminescence methoda bone parameters in the intervention versus control group was (interassay cell volume [CV]ϭ2%), and serum bone-specific compared using a repeated-measures ANOVA.
alkaline phosphatase was measured using an immunoenzy-matic methodb (interassay CVϭ5%). Deoxipiridinoline and N-terminal telopeptide were measured using a 1-step chemolu- Women who received the active intervention were similar to minescence methoda (interassay CVϭ3%) and immunoenzyi- controls in age, baseline muscle power, years since menopause, matic methodc (interassay CVϭ10%), respectively. To collect anthropometric measures, routine biochemical measurements, the 2-hour morning urine, participants were instructed to get up and biomarkers of bone turnover (table 1). Final measurement early in the morning and void. After 2 hours of fasting, during of the primary outcome (muscle power) was obtained in 29 of which only ingestion of water was allowed, participants voided the 33 women who had been originally randomized (14 active again, and all urine samples were collected and used for mea- treatment, 15 controls). Dropouts in the intervention group surements. To assess muscle power, participants, starting from were caused by family problems (nϭ2) and knee pain (nϭ1).
a standstill, jumped as high as possible and landed on a force- In 1 control, a measure of muscle power at the final follow-up plated that measured ground reaction forces.15 The best of 4 could not be obtained because of posttraumatic muscle pain.
attempts was used in the analysis. The acceleration of the After 6 months, muscle power improved by about 5% (from center of gravity (COG) was calculated as the ratio of force (N) 178.9Ϯ9.6W to 187.3Ϯ9.5W) in women who received the and body mass (kg). The integration of acceleration by time active treatment (table 2), whereas it declined slightly in con- gives the instantaneous velocity of the COG (m/s). The power trols. In a repeated-measure ANOVA, change over time in (W) is obtained as the product of force and velocity. Tibial muscle power differed statistically between the 2 groups bone density, mass, and geometry were assessed by a recent (PϽ.02). Overall, muscle power improved in 80% of the generation, high-resolution, peripheral quantitative computed women in the treatment group and in 46% in the controls tomography device (XCT 2000d). Volumetric total bone den- (Pϭ.06). The velocity increased in the intervention group to a sity (mg/cm3) was measured as the average density of the similar extent as the power (from 163.7Ϯ6.2m/s to 171.7Ϯ whole cross-section of the tibial metaphysis (4% of the tibial 5.3m/s, PϽ.005), whereas muscle force did not change signif- length from its distal end); that is, the section mainly composed of trabecular bone surrounded by a thin cortical shell. At the Cortical bone density remained stable in the intervention same site we assessed trabecular bone density (mg/cm3) by group, whereas it declined significantly in the control group excluding cortical bone. Measures of cortical bone density (PϽ.05). However, in a repeated-measure ANOVA, the de- (mg/cm3) and cross-sectional area (mm2) were obtained from a cline in cortical bone density over time did not differ statisti- Arch Phys Med Rehabil Vol 84, December 2003
Table 1: Characteristics of the Participants at Baseline
Abbreviations: BMI, body mass index; HRT, hormone replacement therapy.
cally between the 2 groups (Pϭ.09). All other bone parameters, occurrence in the life of a woman, perhaps contributing to including biochemical indices of bone turnover, did not change physical frailty and mobility disability in late life.2 Studies17 significantly during the study period in either group.
have demonstrated that such a decline may be slowed by Transient, slight lower leg itching and erythema, a known strength training exercise. However, the compliance of older side effect of the vibration exercise,16 was also observed in 6 of persons in traditional exercise programs is poor.
17 treated participants in this study. In no case, however, did High-frequency vibration on a ground-based platform stim- this problem persist after the first 3 training sessions or cause ulates continuously alternating reflex contractions of flexor and interruption of the intervention. Knee pain of moderate inten- extensor muscle groups of the lower extremities.11 We hypoth- sity, without objective clinical signs, was observed in 2 over- esized that vibration is a special type of exercise that may be weight participants with preexisting knee osteoarthritis. The particularly suitable for older persons. It does not require much pain subsided in both participants after a few days of rest. One time or effort, does not cause potentially traumatic vertical of them, however, refused to continue and was dropped from displacements of the involved joints, and specifically trains type II muscle fibers, which are selectively lost during theaging process.16,18 The availability of a simple, safe, and well- DISCUSSION
accepted training method that can improve muscle power in In the present study, 200 minutes of high-frequency whole- postmenopausal women opens a new perspective for the pre- body vibration, distributed in biweekly sessions over 6 months, vention of age-associated loss of muscle function in this group improved muscle power and the velocity of movement in postmenopausal women without significant changes in muscle Previous studies have demonstrated that vibration exercise force. These results suggest that vibration training improves improves bone mineral density in animal and human models.
muscle power mainly by enhancing the pattern of recruitment Our findings provide a possible explanation for this effect of vibration exercise. Mechanical stress produced by muscle con- This study is the first to show an improvement of muscle traction plays a critical role in the maintenance of bone power in postmenopausal women using vibration exercise. The strength.19,20 Thus, improvement in muscle force and power decline in muscle power is an early and apparently inexorable may be a strategy for improving bone characteristics and pre- Table 2: Effect of 6 Months of High-Frequency Vibration Training on Muscle and Bone Parameters
Trabecular volumetric bone density (mg/cm3) Cortical volumetric bone density (mg/cm3) *Testing whether change over time in the specific parameter differed between groups.
†Mean values are calculated only with subjects who had valid measures both at baseline and at 6-month follow-up.
Arch Phys Med Rehabil Vol 84, December 2003
venting osteoporosis in postmenopausal women. In accordance 5. Rubin C, Xu G, Judex S. The anabolic activity of bone tissue, with this hypothesis, our study showed that the decline in suppressed by disuse, is normalized by brief exposure to ex- cortical bone density tended to be greater among control tremely low-magnitude mechanical stimuli. FASEB J 2001;15: women than among women who received the active treatment.
Our findings on cortical bone volumetric density are consistent 6. Rubin C, Turner AS, Bain S, Mallinckrodt C, McLeod K. Anab- with earlier reports21 and support the hypothesis that vibration olism. Low mechanical signals strengthen long bones. Nature exercise may positively affect bone characteristics.10 However, clinical trials that address these issues would require longer 7. Rubin C, Turner AS, Muller R, et al. Quantity and quality of follow-up and, probably, a more intensive intervention. Based trabecular bone in the femur are enhanced by a strongly anabolic,noninvasive mechanical intervention. J Bone Miner Res 2002;17: on earlier reports and on the present findings, our conclusion is that vibration exercise may be a more useful tool for the 8. Flieger J, Karachalios T, Khaldi L, Raptou P, Lyritis G. Mechan- prevention and treatment of osteoporosis than pharmacologic ical stimulation in the form of vibration prevents postmenopausal treatment of osteoporosis,22,23 a disease that is generally under- bone loss in ovariectomized rats. Calcif Tissue Int 1998;63:510-4.
9. Ward KA, Alsop CW, Brown S, Caulton J, Adams JE, Maughal Z.
The vibration training was safe overall. The only clinically A randomised, placebo controlled, pilot trial of low magnitude, significant side effect was knee pain, which was observed in 2 high frequency loading treatment of low bone mineral density in participants with preexisting osteoarthritis of the knee. This children with disabling conditions [abstract]. J Bone Miner Res pain caused cessation of treatment in 1 subject. The frequent occurrence of transient lower leg erythema reported16 previ- 10. Eisman JA. Good, good, good . . . good vibrations: the best option ously was often observed in the present study, but it was for better bones? Lancet 2001;358:1924-5.
always transient, mild, and not disturbing.
11. Seidel H. Myoelectrical reaction to ultra-low frequency and low The present study has several limitations. First, the small frequency whole body vibration. Eur J Appl Physiol 1988;57:558-62.
number of participants and the relatively short duration of the 12. Ferrucci L, Russo CR, Lauretani F, Bandinelli S, Guralnik JM. A intervention might have prevented us from identifying treat- role for sarcopenia in late-life osteoporosis. Aging Clin Exp Res ment effects on secondary outcomes such as muscle force or bone parameters. However, the effect on the primary outcome, 13. Frost HM, Ferretti JL, Jee WS. Perspectives: some roles of me- muscle power, was small but clear-cut and therefore unlikely to chanical usage, muscle strength, and the mechanostat in skeletal be due to chance. Likewise, the treatment’s safety clearly needs physiology, disease, and research. Calcif Tissue Int 1998;62:1-7.
to be tested in larger studies. Second, the compliance with the 14. Turner CH. Three rules for bone adaptation to mechanical stimuli.
treatment sessions was suboptimal; in fact, only 34 of 44 sessions were attended on average. However, an important 15. Rittweger J, Gunga HC, Felsenberg D, Kirsch KA. Muscle and bone-aging and space. J Gravit Physiol 1999;6:P133-6.
reason for the low attendance was the restricted choice of days 16. Rittweger J, Beller G, Felsenberg D. Acute physiological effects and time offered to the participants for the training sessions of exhaustive whole-body vibration exercise in man. Clin Physiol (because of our lack of financial resources). The training was perceived as very useful by the participants, who uniformly 17. Nied RJ, Franklin B. Promoting and prescribing exercise for the reported an improved well-being as a consequence of the elderly. Am Fam Physician 2002;65:419-26.
training. Moreover, it can be considered a striking finding of 18. Evans WJ. What is sarcopenia? J Gerontol A Biol Sci Med Sci this study that a substantial improvement in muscle power was obtained with only 200 minutes of training.
19. Schonau E. The development of the skeletal system in children and the influence of muscular strength. Horm Res 1998;49:27-31.
20. Blain H, Vuillemin A, Teissier A, Hanesse B, Guillemin F, Jeandel C. Influence of muscle strength and body weight and The results of this small RCT suggest that high-frequency composition on regional bone mineral density in healthy women vibration exercise is a feasible, safe, convenient, and effica- aged 60 years and over. Gerontology 2001;47:207-12.
cious intervention, which could prevent the decline in muscle 21. Adami S, Gatti D, Braga V, Bianchini D, Rossini M. Site-specific and bone strength in postmenopausal women. Such interven- effects of strength training on bone structure and geometry of tion can easily be added as a component of an exercise-based ultradistal radius in postmenopausal women. J Bone Miner Res prevention program or even prescribed as the sole intervention when traditional exercise is not feasible.
22. Ferrucci L, Benvenuti E, Bartali B, et al. Preventive health care for older women: life-style recommendations and new directions.
Aging Clin Exp Res 2000;12:113-31.
23. Marcus R. Role of exercise in preventing and treating osteoporo- formed all of the biochemical measurements.
sis. Rheum Dis Clin North Am 2001;27:131-41.
24. Siris ES, Miller PD, Barrett-Connor E, et al. Identification and 1. Thomas M, Fiatarone MA, Fielding RA. Leg power in young fracture outcomes of undiagnosed low bone mineral density in women: relationship to body composition, strength, and function.
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2. Suzuki T, Bean JF, Fielding RA. Muscle power of the ankle 25. Chesnut CH III. Osteoporosis, an underdiagnosed disease. JAMA flexors predicts functional performance in community-dwelling older women. J Am Geriatr Soc 2001;49:1161-7.
3. Mazzeo RS, Tanaka H. Exercise prescription for the elderly: Suppliers
current recommendations. Sports Med 2001;31:809-18.
a. Medical Systems, Via Rio Torbido 40, 16165 Genoa, Italy.
4. Russo CR. High frequency vibration exercise: evaluation of a new b. Quidel Ltd, Via Gobetti 2, 20017 Rho, Milan, Italy.
treatment through a prospective, randomised, controlled trial. Pa- c. Bouty, Via Casiraghi 471, 20099 Sesto S. Giovanni, Milan, Italy.
per presented at: the XII National Meeting of the Italian Society of d. Unitrem, Via Gioia Tauro 22, 100040 Morena, Rome, Italy.
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