Motor learning and Parkinson disease: Refinement of movement velocity and endpoint excursion in a limits of stability balance task.

OBJECTIVE To investigate the effects of practice on performance and retention of a balance task in persons with Parkinson disease (PD). METHODS Ten persons with PD and 10 age and gender-matched healthy control subjects were tested on an anticipatory, static base of support, limits of stability (LOS) balance task on a force plate. The motor learning paradigm utilized for all subjects included an acquisition phase and retention tests at 24 h and 1 week after acquisition. A force plate was used for testing and to collect outcome measures including movement velocity (MVL), endpoint excursion (EPE), and directional control. Data were analyzed for differences between groups and change over time. RESULTS Persons with PD demonstrated performance deficits relative to controls for MVL at all testing periods (P < 0.05), and initially for EPE (P < 0.05), but were able to maintain significant improvements through retention testing relative to baseline (P < 0.05). CONCLUSIONS Persons with PD demonstrated unimpaired capacity for motor learning in a LOS balance task for MVL and EPE, although performance deficits remained for MVL. The results concur with previous motor learning research of upper extremity tasks by suggesting that individuals with mild to moderate PD exhibit a preserved ability to benefit from practice as a means of improving balance task performance.