RELATIONSHIP OF LOWER-LIMB MUSCLE TORQUE AND LOCOMOTOR PERFORMANCE IN PEOPLE WITH PARKINSON?S DISEASE

Introduction: Parkinson?s disease (PD) is a chronic and degenerative disorder of the basal ganglia that causes bradykinesia, tremor, rigidity and postural instability. Subjects with PD also show asymmetric muscle weakness and disorders in functional activities, such as in gait and in stair climbing. Few studies have focused the relationship between muscle torque and functional performance in parkinsonians. Objective: The aim of this study was to identify which muscle groups in the lower limbs are best predictors of gait speed and stair-climbing speed in people with PD. Methods: Seventeen subjects with idiopathic PD who were able to walk and climb stairs independently participated in this study. Participants were separated in two groups (mild and moderate) according to the Hoehn and Yahr Modified Scale. Mean outcome measures included self-selected gait speed, stair-climbing speed and bilateral maximum isometric muscle torque of hip flexors and extensors, knee flexors and extensors and ankle dorsiflexors and plantarflexors. Maximum isometric muscle torque was measured with a hand-held dynamometer while time spent to walk through the walkway and to climb stairs was measured with a digital stopwatch. In each subject, the lower limb with lowest torque values was classified as ?the weakest limb?. Descriptive statistics and stepwise multiple regression analysis were carried out for data analysis. Results: Mean age of subjects and mean time since onset of disease were, respectively, 60.41 ? 9.82 years and 5.58 ? 3.30 years. Mean gait speed was 1.12 ? 0.23 m/s and mean stair-climbing speed was 83.04 ? 24.13 stairs/s. All subjects demonstrated a significant difference in muscle torque between lower limbs. In the moderate group, regression analysis revealed that isometric torque of hip flexors of the weakest limb was the most important independent variable for predicting gait speed (R2= 0.78) and stair-climbing speed (R2= 0.73). There was no relationship between the variables studied in the mild group. Conclusions: Muscle weakness is an important aspect in functional performance for patients with PD. For moderated parkinsonians individuals, isometric muscle torque of hip flexors of the weakest limb explained 78% and 73% of the variability in gait and in stair climbing speeds, respectively. Future studies should verify if gains in strength of hip flexors of the weakest limb could improve gait and stair-climbing speeds in people with PD.