In the proposed studies, the investigators will employ a tiered screening strategy with inexpensive and non-invasive olfactory testing in drug-induced parkinsonism patients followed by DaT imaging in individuals with olfactory impairment to identify a cohort of patients with presumed prodromal PD. Subjects with presumed prodromal PD will then be randomized to a home-based exercise intervention ({5} times weekly aerobic walking confirmed by remote activity monitors) or no intervention. In this cohort, the investigators will assess: 1) Short-term symptomatic effects of exercise on motor function in drug-induced parkinsonism using standard clinical measures (Unified Parkinson's Disease Rating Scale) and quantitative gait assessments after 8 weeks of intervention; 2) a potential disease-modifying effect after 52 weeks of exercise by comparing the rate of change in quantitative DaT imaging; and 3) the mechanisms and biochemical correlates of exercise-induced changes using a panel of serum biomarkers implicated in exercise and/or PD risk including brain-derived neurotrophic factor, uric acid, and apolipoproteinA1. Differences in the rate of change between groups will be assessed using independent samples t-tests and linear mixed-effects models adjusting for age and gender. The investigators' preliminary data demonstrates a strong association between olfactory impairment and abnormal DaT imaging in drug-induced parkinsonism. Based on power calculations allowing for 20% dropout, the investigators will screen approximately 250 drug-induced parkinsonism subjects using olfactory testing, with the expectation that approximately 88 will have abnormal DaT imaging and agree to participate in the intervention trial.