Transmissibility of whole body vibration stimuli through human body in different standing postures

This study focuses on the transmissibility of whole body vibration stimuli through human body in different standing postures to explore the mechanism in which vibration stimuli could be better used as a regimen for bone loss. Five volunteers were guided to stay at three standing postures and imposed of frequency-adjustable vibration stimuli on the plantar surfaces side-alternately. Motion capture system was used to acquire the vibration signals at head, pelvis, knee up, knee down and ankle, from which the transmissibility of vibration stimuli can be obtained. The results showed that transmissibility of vibration stimuli was closely correlated with frequency and skeletal sites. Transmissibility of vibration stimuli in head was much smaller than any other skeletal sites. Transmissibility in the ankle was always in the vicinity of unit one in all the three postures for the vibration stimuli applied side-alternately on the plantar surfaces of both feet. There was an obvious peak around 9 to 11 Hz in the transmissibility curves for knee joint and pelvis. In the resonant peak, transmissibility of vibration stimuli in knee joint and pelvis both exceeded unit one and reached 150%. As the frequency increased after 11 Hz, transmissibility of vibration stimuli decayed rapidly as a function of frequency and dropped to 25% at 30 Hz. This study may help to gain insight into the interaction mechanism between mechanical vibration stimuli and the responses of human musculoskeletal system.