Adaptation process for standing postural control in individuals with hemiparesis

Purpose.To study the adaptation process for standing postural control in patients with hemiparesis after stroke. Methods.The changes of a standing posture developed in nine hemiparetic patients who had never maintained an upright stance alone (aged 4862 years; 619 days after stroke) was evaluated by recording ground reaction forces and surface electromyographic (EMG) from lower limbs. A 60-s standing trial without any instruction about body alignment was repeated five times, and the experience-related changes of centre of pressure (COP) and integrated EMG data were estimated. Results.In the early standing trials, patients balanced themselves by managing the average COP position around the midline of both feet, accompanied by increased muscular activity of the non-paretic leg. COP displacement gradually decreased in the later standing trials (P<0.05). Postural adaptations were achieved by shifting the centre of body sway to the side of the non-paretic foot (P<0.05) while reducing biceps femoris muscular activity (P<0.01) in the non-paretic leg. Conclusions.This study revealed that weight-bearing asymmetry might contribute to improving increased body sway and muscular over-activity of the non-paretic leg. When planning rehabilitative treatment for hemiparetic patients, we should consider that weight-bearing asymmetry may be a result of systematic postural control.