Biomechanics of Vibration Exercise

Abstract

This biomechanistic approach of vibration exercise discusses the human body as a group of segments (foot, shank, thigh, trunk, head) balanced on top of each other. These segments are interlinked by joints, the stiffness of which is generated by the surrounding muscles. Reflexes and pre-tension of the muscles are important factors that modulate the apparent joint stiffness and leg stiffness. In addition, leg stiffness is also affected by posture, with greater leg stiffness occurring in erect posture than in a crouched posture. To ensure comfort and to reduce the possible risk, vibration transmission to the head should be attenuated. This can be achieved by adjusting the pre-tension and posture. In addition, raising the heel from the vibration platform reduces vibration transmissibility. For similar reasons, side-alternating platforms have lower transmissibility to trunk and head than side-synchronous platforms, as they allow an additional degree of freedom in the lumbo-sacral joint. Finally, vibration elicits stretch-shortening cycles within the tendon and skeletal muscle, at a minimum of 6 Hz. These mechanical stretch-shortening cycles provide a solid rationale for the activation of mono-synaptic stretch reflexes.