Strategies for arm stability in post-stroke hemiparesis - biomed 2009.

This aim of this study was to evaluate the ability of hemiparetic stroke subjects to adapt to reaching in an unstable force field compared to the adaptation experienced by healthy subjects reaching in the same environment. Endpoint stability, muscle activity and grip force were measured while subjects made planar reaches while holding a two-joint robotic arm. Neurologically intact (NI) individuals adapted to the divergent force field while reaching by increasing muscle co-contraction in the arm and tightening hand grip. Chronic stroke (CS) survivors began with higher levels of muscle activation and grip pressure, but did not show signs of adaption to the destabilizing force field. Weakness and saturated muscle activity could contribute to the CS subject's inability to adapt. Knowledge of proper and improper sensorimotor adaptation to unstable environments could help determine the most appropriate therapy for increasing strength and muscle activation during reaching.