This study used a unique holographic technique to evaluate the effects of vibration on soft tissues and bones. It was possible to record forced whole-body vibration in humans by holograph interferometry using a double-pulsed ruby laser. The study investigated the manner in which the muscles of the back and vertebral column are affected by vibrations applied to the human buttocks in the sitting position. The subject was exposed to vibration at two frequencies: 40 and 60 Hz (vertical Z axis). Transmission of the vibrations along the subject's back was recorded by means of double-pulsed holography and electromyography. Evaluation of the vibration pattern showed that the vibrations are transmitted along the back all the way up to the neck and head. The pattern of vibration in the muscles of the back and vertebral column showed that the greatest effect was exerted on the lumbar region of the back and the area of transition between the thoracic and cervical regions.
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