Analysis of lower-limb muscle activities during whole body vibration with different standing postures

Based on inverse dynamics, the muscle activities and joint forces of the subject lower limb with knee normal and knee lock postures under vertical whole body vibration with the frequency of 30Hz and the acceleration of about 0.5g were analyzed using AnyBody Modeling System. Using the Motion Capture System displacements of the marked points on the lower limb were monitored during vibrating process with two different standing postures. At the same time the sEMG signals were recorded. In AnyBody Modeling System, the simplified Model of the lower limb were driven by the marked point displacements to calculate the muscle activities such as rectus femoris, gastrocnemius, etc and knee and ankle joint forces. The comparison between the experimental sEMG signals and the calculated results indicated that the model prediction is coupled with the experiments. The results also show that the vibration countermeasure could be as a physical training method to affect the musculoskeletal system and standing posture causes changes in muscle activities and joint forces during the vibrating. So when the vertical whole body vibration is used for subjects with musculoskeletal disorder, the standing posture should be considered according to the individual cases.

I. Introduction

Recently vertical whole body vibration with a low frequency and amplitude as a physical training method for the musculoskeletal system has been with more and more research and tentative application [1] – [4]. The previous research indicate that the vibration could well effect on the skeletal system directly to change bone mineral content [2]; also it could set off excitation of the muscular spindle and increase muscle the spontaneous contraction to change strain stress on the skeletal correspondently [3]. And those changes caused by the vibration with special frequency could be better for the musculoskeletal system.