Analysis of rhythm adjustment mechanism of human locomotion against horizontal perturbation

Human locomotion is considered to be realized using rhythmic signal generated in central pattern generator (CPG). When perturbation is applied during locomotion, a mechanism that adjust the rhythm of CPG based on the timing of foot-contact or foot-lift, called `phase reset' has been proposed and the contribution of such a mechanism on the stabilization has been indicated. In order to verify the existence of phase resetting mechanism, this research measured the human locomotion with perturbation and investigated the transition of rhythm after the perturbation. As a result, adjustment of motion rhythm terminated after foot-contact even the phase difference between after the termination and before perturbation remained. This result indicates the existence of CPG tuning i.e., phase reset. Present research further analyzed the rhythm adjustment of synergies by extracting synergy using singular value decomposition, and found no difference in phase characteristic among synergies. This result indicates the rhythm tuning does not work for each synergy but works on the rhythm generator.