Analysis of joint stiffness of human posture in response to balance ability and limited sensory input during dynamic perturbation

Joint stiffness causes posture movement restriction. However, how joint stiffness responds towards imbalance still remain unclear. The objective was to observe the relationship between the joint stiffness value with balance ability and the efficient amount of stiffness required to maintain posture sway. Moreover, the effects of limited sensory inputs were also discovered. The joint motion at different external perturbations was recorded when different sensory inputs were applied. The results showed that the measurements of joint stiffness displayed imbalance; whereby, less-balanced individuals produced a high stiffness value correlating with the functional reach test (FRT) score. Furthermore, the stiffness value at the joints produced a significant difference with different sensory conditions and when various perturbation frequencies were applied (p < 0.05). The stiffness ratio between joints was also obtained. This study had successfully acquired the correlation between joint stiffness with balance ability, sensory inputs and joint synergy which crucial to maintain the posture balance.