Postural control for different perturbation during walking in humans

Abstract

We examined the effect of unexpected backward perturbation (BP) and dorsiflexion perturbation (DP) on postural control strategy during walking in humans. We measured both kinetics; the vertical component of ground reaction forces (VGRF) from reaction force, and kinematics data; lower limb joint angle and center of mass (COM), together with electromyography activities (EMG) of lower limb muscles. The BP and DP were occurred by six-axis parallel link mechanism platform at heel contact. Results indicated that medial gastrocnemius (MGAS) of the perturbed leg during BP and DP indicated larger response than normal walking. The latency of this response was longer than 100[ms]. Therefore, it suggested that the MGAS response might be not short-latency reflex response for perturbation, but might be long-latency reflex response. The stimulation intensity of BP for ankle joint was smaller than the DP, however the BP COM forward displacement was larger than the DP from O to 300 ms after MB onset. The voluntary responses of human posture control of BP are depended on the COM position.