Perturbation-based training enhances anticipatory postural control in individuals with chronic stroke: a pilot study.

Individuals with stroke commonly have impaired balance control. The aim of this study was to investigate the effect of targeted intervention on anticipatory postural adjustments (APAs) and postural control in people with stroke. Six participants with unilateral hemiparesis due to a stroke (5.0-8.4 years post stroke) participated in a two-phase random crossover study. The participants received in counterbalanced order (a) 2 weeks of experimental, targeted intervention (pushing a medicine ball attached to the ceiling using their unaffected upper extremity) and (b) 2 weeks of control, self-guided general mobility exercise program with a 1-week washout period in between. All study participants were assessed with laboratory tests before and after each intervention. Lab tests included predictable external perturbations induced by a pendulum impact and clinical assessments of balance. Bilateral electromyographic activity of eight trunk and leg muscles and center of pressure (COP) displacements were recorded, and data during the anticipatory and compensatory phases of postural control were analyzed. After the experimental intervention, as compared to control intervention, the participants showed earlier APA onsets (P < 0.05), smaller COP displacements (P < 0.05), and improved [although not significantly (P >0.05)] scores of clinical tests of balance. The results of this feasibility study provide a foundation for developing balance rehabilitation protocols focused on improving APAs in individuals with neurological disorders.