ADAPTATION OF VOLUNTARY STEP INITIATION IN PERSONS WITH PARKINSON'S DISEASE.

Abstract

Purpose/Hypothesis: Difficulties with gait initiation and other locomotion activities are characteristic and often debilitating problems for people with Parkinson's disease (PD).Anticipatory postural adjustments (APAs) for lateral weight shift and stability normally precede and accompany step initiation. Patients with PD demonstrate prolonged and reduced APAs and delayed step initiation. A lateral postural assist at the pelvis has been shown to acutely decrease APA duration and step onset time in PD. The aim of this study was to determine if patients with PD would adapt to lateral assist training by demonstrating decreases in APA duration and step onset time following removal of lateral assist. Number of Subjects: 6 patients with early-stage PD (Hoehn and Yahr stage 1 & 2) and 6 age-matched controls. Materials/Methods: Ground reaction forces were recorded with two force platforms to determine APA characteristics based on the net medio-lateral center of pressure displacement. Whole body kinematic data were recorded using a 6-camera infrared motion analysis system to determine step characteristics. The lateral assist training session consisted of 3 blocks of trials during rapid forward stepping: 10 baseline trials, 50 trials with lateral assist, and 10 post-assist trials without assist. Ten retention trials without assist were collected one week after the initial session. The lateral assist was provided by a motor driven robotic system with a cable attachment hooked onto a belt around the subject's pelvis. The assist was applied when 55% of the subject's weight was on the swing limb to aid with weight transfer during the APA phase of step initiation. Data was analyzed using ANOVA (p < 0.05). Results: There were no significant group effects between PD and control subjects. However, PD subjects tended to show longer APA duration and slower step onset times compared to controls. Significant condition effects between baseline and lateral assist trials, indicated a decrease in total APA duration (p < 0.01), thrust phase (APA onset to peak amplitude (p < 0.02), unloading phase (peak APA amplitude to end of APA, (p < 0.02), and step onset time (p < 0.01). There was a significant decrease in thrust duration between baseline and retention (p = 0.01).A decrease in APA duration between baseline and retention was marginally significant (p = 0.06) and a shorter step onset time approached significance (p = 0.11). Conclusions: This study supports previous research that a lateral assist can acutely improves step initiation characteristics, in patients with PD. A trend for subjects to retain shorter APA duration and step onset with practice suggested a potential for adaptation. Greater significance may have been achieved with larger sample size. Clinical Relevance: The approach illustrates application of current theories of neural plasticity pertaining to adaptive mechanisms of posture and locomotion interactions and their management in people with PD. To attain greater training effects patients may benefit from increased practice time and additional rest breaks to optimize neural adaptation and minimize fatigue.