This study is designed to compare the initial (six months), and then long-term (2 years) effect that 2 different exercise programs (progressive resistance program or flexibility program) have on neuro-physiological, motor, functional, and quality-of-life issues in individuals with Parkinson's disease. The goal is to determine which program is most beneficial. Results from this study will be used to determine which exercise program produces the most beneficial effects on neuro-physiological, motor, functional and quality-of-life measures.