Relationship Between Lower Extremity Muscle Function And Gait Variability In Individuals With PD

Abstract

PURPOSE: Increased variability in motor function can significantly impair performing activities of daily living. The difficulty in performing daily motor tasks is increased in pathological populations, e.g., Parkinson’s disease (PD). The muscular capabilities, e.g., torque production and force control, in PD, are reduced compared to older adults. It is unclear if the reduced muscular capabilities in PD are related to increased difficulty performing regular movements, i.e., gait. This study examined the relationship between muscular capabilities of the lower extremity and gait variability in persons with PD. METHODS: 12 PD and 11 age-matched controls underwent gait and lower extremity muscle testing. Gait was evaluated by having the subjects perform ten over-ground walking trials over a 9-m walkway at a self-selected speed using an 8-camera motion capture system. Linear measures of gait, including stride length, stride time, step width, and velocity, were calculated. Gait variability and force variability were examined using the coefficient of variation (CV = standard deviation/mean × 100%). Lower extremity testing consisted of 1) maximal isometric torque production and 2) submaximal force control using a tracing paradigm at 5, 10, and 20% of their maximal torque production in multiple directions at the hip and ankle. Pearson's correlations were applied to analyze associations between gait variability and force variability. RESULTS: In the PD group, stride time was positively correlated with 20% of ankle dorsiflexion CV (r(21)=.62, p<.05) and velocity was positively correlated with 10 and 20% of ankle plantarflexion CV (r(21)=.59, p<.05) and 20% of hip extension CV (r(21)=.63, p<.05). Maximal torque production of the dorsiflexors (r(21)=.75, p<.05) and plantar flexors (r(21)=.67, p<.05) were positively correlated stride time variability in the PD group. CONCLUSION: The results highlight an association between lower-extremity muscle function and gait function in PD. Interestingly, in those with PD, both maximal strength and control of muscle strength were found to be related to the temporal parameters of gait variability. These results suggest that gait dysfunction could be the result of specific pathological impairments and provide unique opportunities for specialized interventions.