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Contributions of Shortening/Lengthening Responses to Multi-Joint Stretch Reflex Response in Able-Bodied Individuals


Eric Perreault, PhD


Our research addresses the role of multijoint stretch reflexes in the control of posture and movement in unimpaired human subjects. It examines the contributions of the long latency responses to the muscle coordination following whole limb perturbations of the arm. Of particular interest is the shortening (and lengthening) responses that involve excitation (inhibition) of a released (stretched) muscle. The joint angle changes associated with the whole limb perturbations are tracked using an optical tracking system. A 3-dimensional biomechanical model of the arm is used to estimate muscle length changes associated with these joint angle changes. These combined with the surface electromyograms (EMG) recorded from 8 muscles in the arm help us observe the patterns of reflex neural activation. Our preliminary results suggest that the multijoint reflex activity seen as a result of end point perturbations have significant contributions from neurally mediated pathways in addition to the biomechanical coupling. This project contributes to understanding of the mechanisms underlying the unimpaired, multijoint control of the arm during functionally relevant tasks.

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