Effects of obstacle crossing on dynamic postural control of Parkinson's disease patients

[Purpose] This study examined whether people with Parkinson's disease (PD) have postural instability while negotiating obstacles starting from a position of a quiet stance compared to healthy older adults. [Subjects] Ten participants (3 males, 7 females; mean age, 67.8 ± 6.16 years) diagnosed with idiopathic PD (Hoehn & Yahr disability scores ranging from 1 to 3) and ten healthy older adults (4 males, 6 females; mean age, 72.2 ± 4.83 years) were enrolled in this study. [Methods] For each trial, the participants stood quietly in a self-selected foot position with each foot on a force platform. The participants were then instructed to begin stepping over a 10 cm high obstacle or initiate gait at their self-selected pace with the right limb in response to the verbal cue "GO", and continued to walk. The subjects' performance was measured by calculating the changes in the center of pressure (COP) displacements in the anteroposterior (A-P) and mediolateral (M-L) directions using two force platforms. [Results] Using the data of both gait initiation (GI) and obstacle crossing tasks combined for both feet, the A-P and M-L displacements of the COP of the older adults were significantly higher than those of people with PD. On the other hand, the mean COP displacement in the A-P and M-L directions between GI and obstacle crossing were similar. [Conclusion] A decrease in the magnitude of the COP excursion in GI and obstacle avoidance reduced the ability of people with PD to generate forward momentum and maintain lateral stability and motion, factors which are highly related to lateral falling.