Effects of limb load on gait initiation in persons with parkinsonʼs disease

Purpose/Hypothesis: Individuals with Parkinson's disease (PD) experience difficulties with posture and locomotion. In gait initiation, anticipatory postural adjustments (APAs) for lateral weight transfer are prolonged and smaller in amplitude with delayed step onset. Persons with PD may show abnormalities in load proprioception during stance and gait that may influence the initiation timing and other step characteristics. The purpose of this study was to examine whether external assistance with APAs through changes in limb loading enhances posture and gait performance. Number of Subjects: 8 subjects with mild to moderate PD (Hoehn & Yahr stage II.5-III) tested while ON medication and 8 age and gender-matched controls. Materials/Methods: Ground reaction forces and the net mediolateral center of pressure (COP) were measured with two force platforms to determine APA characteristics. Whole body kinematic data were recorded using a 6-camera infrared motion analysis system to determine step parameters. Subjects performed 5 blocks of 6 trials of rapid, self-paced forward stepping. Following an initial baseline walking condition with no platform manipulation, participants received either an air-driven elevation or drop of the single stance limb support surface (1.5 cm in 150 ms), with the order of presentation rotated between subjects. The manipulations were externally triggered during the APA phase of gait initiation when the vertical load was reduced by ∼5% body weight under the stance limb. A second baseline condition was followed by the converse elevation or drop, and fnally a third baseline condition. Data was analyzed using repeated measures ANOVA (p