Neuromuscular Characteristics and Physical Function in Participants with Parkinson’s Disease

Abstract

PURPOSE: This study aimed to investigate the level of physical function, lower body strength, and muscle activation during various types of muscle contraction in participants with and without Parkinson’s disease (PD). METHODS: Twelve participants with PD (mean age=63.17±6.24 years) and 12 age- and sex-matched healthy adults (mean age = 58.67±6.39 years) were recruited. An isokinetic dynamometer was used to measure the length- and velocity-dependent maximum voluntary force and the rate of torque development (RTD) of the knee extensor muscles. Muscle activation of the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) muscles of both legs was examined using surface electromyography. The 6-minute walk test, chair stand test, timed up-and-go test, sit-and-reach test, and back-scratch test were performed to assess physical function. RESULTS: Compared to healthy individuals, participants with PD showed significantly lower maximum voluntary force and RTD (p<.05), performed fewer repetitions in the chair stand test (11.64±1.75 vs. 17.08±2.27, p<.001), were slower in the timed up-and go test (8.36±1.42 vs. 5.65±1.07, p<.001), and walked shorter distances in the 6-minute walk test (424.17±65.97 vs. 539.47±63.18, p<.001). However, activation of the three different muscles during isometric and isokinetic muscle contraction was not different between participants with and without PD. CONCLUSIONS: Preserved muscle activation and significantly lower muscle strength during various types of muscle contractions may suggest lower muscle strength and efficiency. The lower physical function seen in participants with mild PD could be due to disease and low physical activity-related muscle atrophy rather than lower muscle activation.