Quantification of reflex activity in stroke survivors during an imposed multi-joint leg extension movement |
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Authors: | iian Black Diane Nichols Marlena Pelliccio Joseph Hidler |
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Institution: | (1) Center for Applied Biomechanics and Rehabilitation Research (CABRR), National Rehabilitation Hospital, 102 Irving Street, NW, Washington, DC 20010, USA;(2) Physical Therapy Service, National Rehabilitation Hospital, 102 Irving Street, NW, Washington, DC 20010, USA;(3) Department of Biomedical Engineering, Catholic University, 620 Michigan Ave., NE, Washington, DC 20064, USA |
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Abstract: | The goal of this study was to compare short- and long-latency reflex responses in eight major lower-extremity muscle groups
following an imposed multi-joint leg movement between a group of 14 chronic (>1 year) stroke survivors and 10 healthy age-matched
controls, and to investigate the influence of joint velocities and muscle excitation levels on these reflex responses in each
respective group. Subjects were seated with their foot anchored to a sliding footplate that could extend their leg. Prior
to the leg being moved, subjects were instructed to pre-activate hip and knee flexors and extensors. Feedback of joint torque
was used to help subjects activate muscles over a range of excitation levels. Following pre-activation, the subject’s leg
was passively extended so the knee or hip joint rotated at one of three different speeds (30, 60, and 120°/s). In general,
it was found that the magnitude of stroke survivors’ reflex response was greater compared to controls’ in certain biarticular
muscles, notably the gastrocnemius and medial hamstring, and the uniarticular adductor longus, and that the long-latency reflex
component (between 40 and 150 ms post-movement) accounted for most of the observed differences. Furthermore, while reflex
response amplitudes increased in both groups with increasing movement speed, the rate of increase was significantly larger
in stroke subjects than in controls. Clinically, these findings may help explain why stroke survivors walk slowly since it
is under these conditions that reflex responses better emulate those of their able-bodied counterparts. |
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Keywords: | Stroke Spasticity Hemiparesis Electromyography Reflex Pre-activation |
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