Aerobic Exercise in Parkinson's Disease

Inclusion Criteria: * Men or women aged 40 and older with the diagnosis of idiopathic PD per UK Brain Bank criteria * Hoehn-Yahr Stage I-III, on stable dopaminergic treatment regimen for equal or greater than 4 weeks prior to baseline. * Aerobic Fitness: VO2max below "very good" fitness levels for their age and gender at baseline cyle ergometry. To include subjects who have room to improve their aerobic fitness, the investigators will enroll only those subjects whose VO2max is below "very good" fitness level (about 90% of the population) using age and gender based VO2max norms based review of 62 studies where VO2max was measured directly in healthy adult subjects in the USA, Canada and 7 European countries (Reference: Shvartz, E and Reibold, RC. Aerobic fitness norms for males and females aged 6 to 75 years: a review. Aviat Space Environ Med. 1990; 61:3-11). * Cognitive function: No dementia per Movement Disorder Society Level I criteria (Reference: Dubois, B, Burn, D, Goetz, C, et al. Diagnostic procedures for Parkinson's disease dementia: recommendations from the movement disorder society task force. Mov Disord. 2007; 22:2314-2324). * Current active drivers with a valid driver's license * Veteran or non-veteran Exclusion Criteria: * Subjects unwilling or unable to give informed consent * Secondary parkinsonism (e.g., drug induced) * Parkinson-plus syndromes * History of brain surgery for PD such as deep brain stimulation * Corrected visual acuity less than 20/50 (due …