The study is a randomized clinical trial, with three treatment arms and four repeated measures: before treatment, after treatment, and follow-up after 10 months and again after 16 months. This study compares usual care based on the National Parkinson's Foundation, aerobic training, and targeted flexibility and functional training. The primary outcomes are measures of overall functional ability, balance and economy of movement. Secondary outcomes include measures of disease state, spinal range of motion, aerobic capacity, and quality of life.