Existing Technology

Whole-body vibration is the mechanical repetitive movement, or oscillatory motion, around an equilibrium point.³⁸ It is delivered through the use of a vibrating platform on which static poses are held or dynamic exercises can be performed, depending on the type and force of the machine. Whole-body vibration exercise is a forced oscillation that transfers energy from a vibration platform to a human body.³³ The vibrations generated by motors underneath the platform are transmitted to the person on the machine. Available vibration exercise platforms produce sinusoidal shaped oscillations described by their frequency, amplitude, and phase angle.³³

The International Society of Musculoskeletal and Neuronal Interactions (ISMNI) developed consensus criteria to describe sinusoidal vibrations, the type of vibration currently used in whole-body vibration platforms. Vibration frequency is defined as the repetition rate of the oscillation cycle, and the frequency of oscillations per second is reported in hertz (Hz). The amplitude, which is the maximal displacement from the equilibrium position, is reported in millimeters (mm). Displacement in mm from the lowest to highest point of the vibrating platform position is the peak-to-peak displacement. Peak acceleration, defined as the maximal rate of change in velocity during an oscillation cycle, is a function of the frequency and of peak-to-peak displacement (meters/second*second). Peak acceleration is often expressed as multiples of Earth’s gravity (9.80665 meters/second*second) denoted by the symbol (g).³⁸ While acceleration can be calculated from reported frequency and displacement, the ISMNI recommends reporting acceleration directly for consistency. Vibration acceleration distinguishes the acceptable dose of therapeutic whole-body vibration, as compared to the hazardous dose of vibration defined by the International Organization for Standardization (ISO). Even though available whole-body vibration platforms are meant to produce sinusoidal shaped oscillations, it is important to note that actual oscillations produced by the platforms may diverge from a pure sinusoidal shape, and the vibrations transmitted to human subjects may depend not only on the vibration parameters but also on the position of the individual on the platform and on the rigidity of the platform plates.³⁸ Characteristics of whole-body vibration modalities are an essential part of patent applications. Patent claims for various platforms include direction, amplitude, frequency, and vibration acceleration (patents 20100049105; 20090269728; 20090076421; 20080009776; 20070290632; 20070225622; 20070219052; 20050251068).

Whole-body platforms can be further categorized by acceleration levels and by the way in which they apply vibration. Platforms that provide acceleration of less than 1 g are considered low intensity while those that provide acceleration of greater than 1 g are considered high intensity. Platforms where the left and right feet move up and down simultaneously are described as operating in a synchronous way. Platforms that use a reciprocating vertical displacement on the left and right side of a fulcrum are described as operating in a side-alternating way.³⁸ Platforms that oscillate in three planes are described as tri-planar or elliptical.⁵⁷ The ISMNI recommends that both the whole-body platform type and intensity be reported.

There are two different theories regarding the optimal settings for a vibration session. One theory proposes using amplitude and frequency settings that do not change during a single vibration session. The other theory proposes using a low amplitude setting along with various frequencies during the vibration session to engage different muscle frequencies.⁵⁸ It is unclear which theory is best for specific individuals and outcomes.

The FDA has not approved whole-body vibration platforms for medical purposes; therefore, no FDA standards regulate their manufacture, and designs vary widely. An example of a whole-body vibration platform is shown in Appendix D. Some low-intensity platforms are small rectangular devices raised several inches off the ground, resembling a bathroom scale in size and shape, while some high-intensity platforms are larger and resemble typical exercise machines. Some platforms have safety features, such as a handrail for balance.

Low-intensity vibration platforms are currently marketed for home use for about $1,600. Some of these platforms automatically calibrate the treatment to each user’s weight and body mass index. Suggested treatment sessions involve standing on the platform for 10 minutes per day. Manufacturers advise that home use requires no supervision. Newer models are very low height and offer an optional wheelchair mount (e.g., www.livtherapy.com/products/index.html). Technological developments currently underway will allow individuals with mobility problems to use vibration platforms in a seated or supine position (e.g., http://vibetechglobal.com/prototype.aspx).

High-intensity vibration platforms produce a gravitational force greater than 1 g regardless of frequency. High-intensity whole-body platforms marketed as exercise equipment are used in clinical physical therapy or rehabilitation settings, exercise facilities, and in the home. Currently, no organization provides accreditation or training for vibration therapy use in professional settings. Some exercise facilities provide proprietary training to personal trainers (e.g., Powerplate, www.powerplate.com) for proper use in exercise programs, but this training is not specific to osteoporosis prevention or treatment.

Whole-body vibration therapy may offer advantages to individuals who cannot continue or do not want to continue or initiate pharmacological treatment to increase bone density. While bisphosphonates are a first line treatment for osteoporosis, associated adverse effects lead to treatment discontinuation in 10-15 percent of patients.⁵⁹ Common adverse effects from bisphosphonates include minimal trauma atypical fractures, esophageal irritation, renal toxicity, acute-phase reactions, gastrointestinal toxicity, and osteonecrosis of the jaw.^5,12,14-17 The percentage of patients persisting with bisphosphonate therapy for 1 year or more ranged from 17.9 percent to 78.0 percent.⁶⁰ Therefore, a large percentage of patients receive no pharmacological treatments to prevent fractures. Whole-body vibration may offer an alternative for individuals unable to perform high-impact exercise, and the ease of use may result in better overall compliance. Disadvantages of whole-body vibration therapy include unknown long-term safety and out-of-pocket costs to the consumer.

Vibration exposure, therapeutic and occupational, presents safety concerns. Vibration has been recognized as an occupational hazard associated with low back pain,^61,62 musculoskeletal problems,⁶³ cardiovascular disorders,⁶⁴ neurovestibular disorders⁶⁵ and Raynaud’s syndrome.⁶⁶ ISO has defined vibration limits for comfort, performance proficiency, and safety based on the known occupational hazards, and ISO 2631-1 defined high intensity vibrations (those that produce more than 1 g force) as hazardous regardless of frequency (http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_tc_browse.htm?commid=51514). Safety concerns for vibration as a therapeutic intervention include the possibility of an individual losing contact with the vibration platform and becoming air-bound when acceleration exceeds 1 g; the resulting impact as the feet return to the platform may be harmful for individuals with fragile bones.³³ Vibration may also be harmful to the soft tissue organs of the head and chest. Further, since vibration transmissibility to the head and trunk can be altered by knee flexion and posture, an individual’s shifting of position on the platform may complicate accurate measurement of vibration in different body parts.³³ Additionally, different body parts have their own resonant frequencies, and vibration platform-induced acceleration at frequencies greater than 20 Hz may match a resonant frequency for a particular body part. This would cause the acceleration experienced in that body part to be greater than those set on the platform, and this amplification may be harmful for individuals with fragile bones.⁶⁷ Nomograms have been developed to estimate the safe length of time, frequency, and acceleration for using different whole-body vibration platforms for exercise based on the ISO standards and known occupational hazards of vibration.⁶⁸

Key informants indicated that harms from whole-body vibration therapy may include plantar fasciitis, itchy legs, blurred vision, tinny hearing (tinnitus), white-finger disease (a secondary form of Raynaud’s syndrome), orthostatic hypertension, and aggravation of soft-tissue and joint injuries. Dislocation of an intraocular lens after cataract surgery may also be a concern, particularly since the population using whole-body vibration for osteoporosis prevention and treatment is at greater risk for cataract.⁶⁹ Since various parts of the human body can resonate at different frequencies, and these frequency resonances can be highly individual, unintended injuries could occur without better understanding of the optimal vibration dosage and transmission to different parts of the body. Other concerns expressed by key informants included loss of balance and falls during platform use and lack of clear distinction between platforms intended for powered exercise and those intended for osteoporosis therapy.

Context in Which the Technology Is Used

Whole-body vibration platforms are used in the home, in clinical physical therapy or rehabilitation settings, and in exercise facilities. Whole-body vibration platforms have not been approved by the FDA for treatment purposes, so unlike therapeutic devices, they have been marketed without vigorous standard testing in clinical trials II-III. Manufacturers of high-intensity whole-body vibration platforms market the devices as powered exercise equipment. These high-intensity whole-body vibration platforms may be used for medical purposes, such as muscle or joint rehabilitation, but they are exempt from the FDA premarket notification procedures [48 FR 53047, Nov. 23, 1983, as amended at 61 FR 1125, Jan. 16, 1996; 66 FR 38818, July 25, 2001]. Manufacturers marketing low-intensity whole-body vibration platforms for treatment of osteoporosis or improvement of bone mineral density (BMD) specify through disclaimers on their Web sites that their device is considered investigational and that they do not make medical claims for osteoporosis (e.g., www.juvent.com, www.marodyne.com/technology). However, many Web sites of manufacturers and distributors of whole-body vibration platforms do provide summaries of, or links to, scientific research papers for potential consumers to review.

The manufacturer suggested billing codes (CPT codes) for therapy procedures include codes 97110, 97112 and 97530. The Medicare Outpatient Therapy Billing defines such codes as therapy services “delivered under an outpatient physical therapy plan of care.” Overall, Medicare payments for outpatient physical therapy increased between 2003 and 2008 by 70 percent, from $631,532,770 to $1,070,996,026, respectively. Since CMS did not specify billing codes for whole-body vibration therapy, we could not determine true utilization of this therapy among Medicare beneficiaries. We found no published articles about utilization of whole-body vibration therapy across other health insurance plans, and we were unsuccessful in locating a health plan key informant who could provide relevant information. Other key informants expressed no awareness of any third-party payers covering costs for whole-body vibration therapy, so individuals pay out-of-pocket for clinical sessions or for platforms for their homes. Manufacturers do not provide information about total sales of whole-body vibration platforms; therefore, we could not determine utilization outside of health care settings.

Current Evidence of the Technology

The literature search yielded a total of 344 studies, with 245 abstracts and full-text articles screened for final inclusion. Only 12 studies met the criteria for the correct patient population, intervention, and outcome measures.^{21,27,30-32,47,52,57,70-73} Studies that were excluded due to patient population (n = 133) included those that examined athletes, healthy and active children and young adults, patients with cerebral palsy, Parkinson’s disease, multiple sclerosis, cystic fibrosis, spinal cord injuries, or those who have suffered a stroke, are bed-ridden, are experiencing pain, or have occupational injuries. We excluded studies (n = 37) that did not evaluate whole-body vibration, such as those that evaluated airway vibration for asthmatics or periodontal vibratory devices. A number of studies (n = 21) that examined whole-body vibration for the patient population of interest but did not assess any bone outcomes were also excluded. Evidence tables for the included studies are shown in Appendix E. Other reviews and background studies on whole-body vibration were retained (n = 42), but data was not abstracted.

Patient Populations

The patient populations included in studies of whole-body vibration therapy for the prevention and treatment of osteoporosis can be classified into three groups: individuals diagnosed with osteoporosis, individuals with low BMD, and individuals at risk for low BMD or osteoporosis. The breakdown of the studies into these three groups is shown in Table 1.

Table 1

Patient populations in vibration studies.

Two studies focused on postmenopausal women diagnosed with osteoporosis.^31,70 Participants in both studies were not previously taking any medications that could affect bone. Women were excluded from these studies if they had any number of conditions such as high blood pressure, heart disease, thrombosis, herniated discs, vertigo, or osteoarthritis.

Three studies focused on children and adolescents with low BMD. One study included male and female children with osteogenesis imperfecta, a disease characterized by brittle bones.⁷¹ One study included female children with endocrine disorders that had low BMD and were not taking any medication that could affect their bones.⁷² The third study included white female adolescents with low BMD who had previously sustained a fracture. Participants in this study had no underlying diseases or chronic illnesses, were not taking any medications, and had completed puberty.⁴⁷

The remaining seven studies evaluated individuals at risk for low BMD or osteoporosis. All but one study of this group evaluated post-menopausal women.^{21,27,30,32,52,57} The other study included one older male participant.⁷³ Five of the seven studies reported that participants were not taking any medications that could affect bone,^{21,27,30,32,57} while two of the seven did not report whether participants were using any medications that could affect their bones.^52,73 Individuals were excluded if they had a number of conditions, such as heart problems, thrombosis, musculoskeletal problems, disorders affecting bone or muscle, orthopedic or arthritic problems, or eye disorders, if they did not have adequate nutrition, or if they were physically unable to complete the vibration protocol.

Vibration Modalities

Studies on vibration therapy for osteoporosis have used synchronous, side-alternating, and tri-planar whole-body vibration platforms. The distribution of studies using these types of platforms is listed in Table 2. All studies using side-alternating platforms have been completed outside of the United States.^21,31,52,71 The tri-planar platform has been used in only one study thus far.⁵⁷ Two studies listed the platform manufacturer but did not explicitly state the type of whole-body vibration platform.^32,73 Studies have examined use of vibration platforms both in the clinic setting, where study participants attended supervised sessions at a research or therapeutic location, and in the home setting, where participants used the platform on their own schedule.

Table 2

Type of vibration platforms used in studies.

Vibration Intervention

The characteristics of the whole-body vibration interventions used in the 12 included studies are presented in Table 3. The vibration intervention varied considerably across the 12 studies. Terminology was also inconsistent for both the platform characteristics and study protocols. No separate calculations were made to determine platform settings; we present here only those explicitly reported in the studies.

Table 3

Characteristics of vibration intervention in studies.

The frequency of the vibration platforms ranged from 12-40 Hz across 11 of the studies, while one study did not report the frequency.⁷³ Five of the studies had frequency settings that changed, either during an individual vibration session or during the intervention study period.^{27,32,52,57,71}

The amplitude ranged from 0.7-5 mm across the seven studies that reported it;^{21,27,31,32,57,70,71} four studies reported only acceleration and not amplitude,^30,47,52,72 and one study reported neither amplitude nor acceleration.⁷³ The amplitude setting changed during the intervention period in one study.³² The seven studies that reported amplitude explained it with various terms, including “amplitude,” “vertical amplitude,” “peak to peak,” and “upwards and downwards.”

The acceleration of the platforms ranged from 0.1-10 g across the six studies that reported it.^{30,32,47,52,57,72} Five studies reported no acceleration but only amplitude,^{21,27,31,70,71} while one study reported neither acceleration nor amplitude.⁷³ The six studies that reported acceleration described it with various terms, including “acceleration,” “acceleration magnitude,” “vertical acceleration,” “peak acceleration,” and “peak to peak.”

Each vibration session ranged from 15 seconds to 30 minutes. Three studies had session lengths that changed during the intervention period,^32,52,57 and three studies had multiple sessions per day.^30,71,73 Six studies included rest periods during the vibration session,^{21,27,32,52,57,71} and one study included rest periods between the multiple sessions per day.³⁰

The vibration session frequency ranged from 1 to 7 days per week. The duration of the vibration intervention ranged from 8-72 weeks, as did the length of followup for analyzing outcomes.

Of the six studies that reported acceleration, three had levels below 1 g,^30,47,72 and three had levels above 1 g.^32,52,57 The three studies with acceleration levels below 1 g used synchronous whole-body vibration platforms with a 30 Hz setting; sessions were more frequent for these studies compared to those reporting acceleration below 1 g (3 or 7 days compared to 2 or 3 days) and the session lengths tended to be longer (10, 20, or 30 minutes compared to 15 seconds to 30 minute total session with warm up and cool down).

Four studies had participants perform dynamic exercises or extend their lower extremities while on the vibration platform.^27,32,57,71 A number of studies instructed participants to flex their knees while standing on the platform^21,31,52,71 and several studies had participants flex their knees while performing exercises on the platform.^27,32,57 Only three studies reported the type of footwear that participants used while on the platform,^21,32,57 and five studies stated, or visually showed, that there was a support device available on the platform.^30,70-73

Three studies evaluated whole-body vibration in addition to another intervention (whole-body vibration plus exercise or resistance training and whole-body vibration plus bisphosphonate use).^27,31,57 Three studies provided Vitamin D and/or calcium supplementation to study participants,^27,47,52 while another two studies advised participants on their calcium intake.^31,57

Outcomes

The distribution of outcomes assessed in the 12 whole-body vibration studies is listed in Table 4. Eleven of the 12 studies measured BMD.^{21,27,30-32,47,52,57,70,72,73} Out of these 11 studies, eight used only a dual-energy x-ray absorptiometry (DXA) to obtain a measure of BMD.^{21,27,30-32,57,70,73} Two of the 11 studies used only computed tomography (CT) to measure BMD,^52,72 while one study used both DXA and CT to measure BMD.⁴⁷ The location of the BMD measurements included the femoral neck, lumbar spine (L1-L4), total body, total hip, trochanter, and forearm. Only one study reported bone mineral content along with the BMD.⁴⁷

Table 4

Outcomes in vibration studies.

Only two studies included fractures as an outcome measure.^31,71 The one study that did not measure BMD counted fractures,⁷¹ and the other study assessed fracture through x-rays at the end of the vibration intervention period.³¹

No studies used a validated measure of quality of life. Only two studies reported minor harms from the vibration intervention.^52,71 It was not clear that harms were systematically collected in all studies; most studies relied on self-report for harms.

Eleven of the 12 studies also evaluated other outcomes.^{21,27,30-32,47,52,57,70-72} The outcomes included bone turnover markers, falls, balance, mobility, back pain, postural control, bone area, muscle force, muscle strength, muscle power, muscle mass, muscle area, fat mass, compliance with study protocol, and efficacy of device use.