Transmission of Vertical Whole Body Vibration to the Human Body

Abstract

ABSTRACT:According to experimental studies, low-amplitude high-frequency vibration is anabolic to bone tissue, whereas in clinical trials, the bone effects have varied. Given the potential of whole body vibration in bone training, this study aimed at exploring the transmission of vertical sinusoidal vibration to the human body over a wide range of applicable amplitudes (from 0.05 to 3 mm) and frequencies (from 10 to 90 Hz). Vibration-induced accelerations were assessed with skin-mounted triaxial accelerometers at the ankle, knee, hip, and lumbar spine in four males standing on a high-performance vibration platform. Peak vertical accelerations of the platform covered a range from 0.04 to 19 in units of G (Earth's gravitational constant). Substantial amplification of peak acceleration could occur between 10 and 40 Hz for the ankle, 10 and 25 Hz for the knee, 10 and 20 Hz for the hip, and at 10 Hz for the spine. Beyond these frequencies, the transmitted vibration power declined to 1/10th−1/1000th of the power delivered by the platform. Transmission of vibration to the body is a complicated phenomenon because of nonlinearities in the human musculoskeletal system. These results may assist in estimating how the transmission of vibration-induced accelerations to body segments is modified by amplitude and frequency and how well the sinusoidal waveform is maintained. Although the attenuation of vertical vibration at higher frequencies is fortunate from the aspect of safety, amplitudes >0.5 mm may result in greater peak accelerations than imposed at the platform and thus pose a potential hazard for the fragile musculoskeletal system.

High-frequency, low-intensity vibrations increase bone mass and muscle strength in upper limbs, improving autonomy in disabled children

“…The signals may not have been transmitted or may have been damped out by sitting. (29) Future studies could examine different frequencies, displacements, and assessment tools.…”

Transmission of low-intensity vibration through the axial skeleton of persons with spinal cord injury as a potential intervention for preservation of bone quantity and quality

“…15 In our study, the LIV signal administered about one-quarter the acceleration due to gravity for the lower-intensity setting, and about one-half the acceleration due to gravity for the higher-intensity setting to the plantar surface of the foot. The P2P accelerations delivered through the appendicular and axial skeleton to the cranium ranged from 25 to 59% of that administered.…”

“…As we become more knowledgeable concerning what bone is most responsive to, in terms of stimulating mechanical adaptation, it does not appear that a larger signal is necessarily better, especially when considering that larger signals are associated with an increased risk of tissue damage. Other studies that have administered LIV have been shown to be safe, [12][13][14][15] and these prior reports have demonstrated potential to increase trabecular bone density and improve bone strength in animal studies, [16][17][18]32,33 with benefits to both bone and muscle. 14,18 In a rat model of disuse with constant hind limb suspension compared with normal weight-bearing animals, LIV administered at 90 Hz and 0.25 g on the hind limb suspended rats for 10 minutes a day, 5 days per week, successfully maintained normal rates of bone formation; experimental animals had suppressed bone formation rates of 72% compared to weight-bearing control animals.…”

“…Pharmacological approaches to prevent bone loss have not been generally accepted as efficacious, and they are not routinely administered. 10,11 However, low-magnitude mechanical signals of lowintensity vibration (LIV) delivered by an oscillating platform have been shown to be safe, [12][13][14][15] easy to administer, and anabolic to bone in both animal [16][17][18][19] and human studies. 14,20 This preliminary evidence, although not yet studied in persons with SCI, has demonstrated efficacy in reducing or preventing bone loss in persons with low bone density, as reported in postmenopausal women 14 and children with cerebral palsy.…”

Whole Body Vibration Training Effects on Bone Mineral Density in Postmenopausal Osteoporosis: A Review

“…Whole body vibration involves a person standing on a vibrating platform in such way that the vibrating stimulus is being directly sent to the plantar surface and then transmitted through the body to bones and muscles [47,48].…”