The goal of the study is to compare different types of high intensity circuit exercises over an 8-class training series in people with Parkinson disease. The main question it aims to answer is:

-Does including arm and hand exercises with leg exercises improve reaction time, balance, functional measures, gait speed and quality of life? This group will be compared to a group that only does leg exercises. Participants will be asked to participate in 8 high intensity circuit exercise classes.

People with Parkinson disease will be recruited from the community and randomized into 2 equal groups: high intensity interval circuit training with lower extremity (LE) and lower and upper extremity (LEUE) training. The study will be composed of a baseline assessment, 8 group class sessions, and a post-intervention assessment. The baseline assessment will include demographics, disease and fall history and outcome measure collection. Group class sessions will include concurrent group warmup, followed by an 8-station circuit performed with high intensity intervals, and a cool-down. The circuit will include 4 stations performed by both the LE and LEUE groups and 4 stations specific to each intervention group, including 4 additional LE exercise stations for the LE group and 4 UE specific stations for the LEUE group. The stations that differ will not be adjacent to one another nor specifically indicated as different. The stations that differ will mirror similar aspects of function (ie, strength, reaction time, etc.) for the UE and LE stations. Participants will be told exercise stations may vary within-session and week to week but will not be informed that only one group has UE exercise interventions. After conclusion of the class series, post-intervention balance and stepping outcomes will be reassessed.

Inclusion Criteria:

• diagnosis of Parkinson's disease
• Hoehn and Yahr level of 1 to 3
• ability to walk independently with or without an assistive device
• obtain medical clearance to participate in moderate or vigorous exercise.

Exclusion Criteria:

• diagnosis of any neurological disease other than PD (including but not limited to stroke, dementia, and multiple sclerosis; mild cognitive impairment is not excluded)
• bone instability (non-consolidated fractures, unstable spinal column, severe osteoporosis)
• muscle or ligament tears
• uncontrolled hypertension
• uncontrolled diabetes
• severe cardiovascular disease that impairs walking or exercise
• a major change in medication during the study training period (pre-test to post-test)

Participants will be told exercise stations may vary within-session and week to week but will not be informed that only one group has UE exercise interventions.

Assessors are blinded to group allocation.