Identification of Central and Stretch Reflex Contributions to Human Postural Control

Human postural control requires continuous modulation of ankle torque to stabilize the upright stance. The is generated by two components: active contributions, due central and stretch reflex, passive mechanisms, joint intrinsic stiffness. Identifying contribution each component difficult, since their effects appear together, standing controlled in closed-loop. This article presents a novel multiple-input, single-output method identify reflex contributions human control. model uses muscle EMGs as inputs no kinematic data. Application data from nine subjects during while subjected perturbations position demonstrated that accounted for 84.0± 5.5% torque. plantar-flexors collectively produced largest portion through control, with large inter-subject variability relative individual muscles. In addition, was substantial half subjects, showing its potentially important functional role; finally, estimated residual model, contributed 15% study introduces new quantify pathways control; also provides an estimate noisy significantly increased signal noise ratio, suitable identification stiffness standing. can be used different experimental conditions minimal a-priori assumption regarding role