Challenging Standing Balance Reduces the Asymmetry of Motor Control of Postural Sway Poststroke

Background: Ankle plantarflexor muscle impairment contributes to asymmetrical postural control poststroke. Objective: This study examines the relationship of plantarflexor electromyography (EMG) with anterior–posterior center of pressure (APCOP) in people poststroke during progressive challenges to standing balance. Methods: Ten people poststroke and 10 controls participated in this study. Anteriorly directed loads of 1% body mass (BM) were applied to the pelvis every 25–40 s until 5%BM was reached. Cross-correlation values between plantarflexor EMG and APCOP (EMG:APCOP) position and velocity were compared. Results: EMG:APCOP velocity correlations were stronger than EMG:APCOP position across all muscles (p < .01), and correlations were predominately stronger in the nonparetic compared with the paretic leg (p < .05). Increasing challenge to standing balance reduced asymmetry of EMG:APCOP relationships. Conclusions: These data suggest that sensory information reflected in APCOP velocity interacts more stron...