Central and Peripheral Fatigue in Individuals With Parkinson's Disease - Evaluation and Training

Fatigue is one of the most common symptoms in individuals with Parkinson's Disease (PD). Past research indicated that more than half of the individuals with PD demonstrated fatigue symptom. The severity of fatigue was also correlated to the quality of life in individuals with PD. Finding the contributions of the central and the peripheral factors to fatigue and developing an effective training program for individuals with PD are very important. Fatigue can be categorized into peripheral or central causes. The central fatigue and voluntary activation failure originate from the decrease in motivation or the reduction of the conduction within corticospinal tracts. Long term activation failure and central fatigue will cause disuse of muscle and result in peripheral weakness and peripheral fatigue. Quantifying the weighting of central versus peripheral factors contributing to the fatigue in people with PD is important. Most of the conventional strength and endurance training programs were based on the researches of young groups. Almost no training program was design for enhancing the voluntary activation level and relief the central fatigue. Seeking an appropriate training program to enhance central activation is very important for individuals with PD who prone to fatigue. Previous studies have shown that increasing afferent input by peripheral electrical stimulation (ES) at sensory threshold enhanced the plasticity of contralateral primary sensory cortex, the excitability of corticospinal tracts, and the functional performance in young adults. Combining afferent input with strength training was more effective than strength training along. ES, which is easy to quantify the dose of afferent input, is a feasible method to provide such training. The purpose of this project is to investigate the effects of the combination of ES at sensory threshold and strength training on voluntary activation in the individuals with PD.