Task-dependent modulation of stretch reflex stiffness in the ankle.

摘要

The stretch reflex is an involuntary contraction produced in response to muscle stretch. Despite extensive research, its role in the control of movement and posture remains controversial. One reason for this is that the torque output produced by reflex activity has been studied in only a limited number of tasks and behaviours. The main thrust of this thesis is to examine whether the central nervous system (CNS) modifies stretch reflex properties to suit the task.;An electro-hydraulic actuator applied perturbations to the ankles of five subjects while they performed position-matching (PM) and torque-matching (TM) tasks. Stretch reflex properties were determined using a new closed-loop, reflex identification algorithm that analytically separated the torques produced by stretch reflexes from the overall ankle torque. Stretch reflex gain was greater in the PM task than for the TM task, under matched conditions.