Changes In Leg Power Are Responsible For Clinically Meaningful Improvements In Parkinson’S Disease

Abstract

Motor function as measured by the Unified Parkinson’s Disease Scale motor subsection (UPDRS-motor) is predictive of disability, disease progression and treatment effect among patients with Parkinson’s disease. Clinically meaningful changes of this measure have been identified. Among physiologic attributes commonly targeted in rehabilitation, we attempted to identify those attributes in which changes led to clinically meaningful differences (CMD) in the UPDRS-motor outcome. PURPOSE: To examine the impact of changes in leg power, leg strength and balance on motor function in older adults with PD. METHODS: Secondary analysis of data from older adults with Parkinson’s disease (n=14, 9M/5F; H&Y stage: I-III; age: 71.6 ± 6.6 y; weight: 77.8 ± 18.8 kg; height: 1.73 ± .1 m; PD duration: 6.9 ± 4.4 y) participating in a 12-week a randomized controlled trial of power training was performed. Leg press power and strength normalized to participants’ body weight was measured using pneumatic resistance machines. Balance was measured through the mini-Balance Evaluation System Test. Motor function was assessed using a continuous outcome defined by recording a moderate CMD of UPDRS-motor score (4.5-6.7 points). Multivariate linear regression models were constructed to evaluate possible confounding between physiologic variables and relevant covariates. RESULTS: After controlling for baseline values of leg power, strength, balance and UPDRS-motor score, leg power was the only attribute in which changes were significantly associated with a CMD in UPDRS-motor score (β=1.14, 95% CI .27, 4.43, p=.032). CONCLUSION: Improvements in leg power, independent of strength and balance, appear to make an important contribution towards clinically meaningful improvements in the UPDRS-motor score. Exercise interventions should be designed to target leg power in order to enhance motor function.