Aerobic exercise is recommended for individuals with Parkinson's disease (PD) and can improve quality of life, both physically and mentally. The most efficacious program to achieve these exercise benefits is unknown. Recently, high-intensity interval training (HIIT) has been shown to be safe and more effective in many high-risk populations with limited exercise tolerance. Shorter bouts of exercise are likely better tolerated in PD due to difficulty sustaining muscle contractions. The goal of this project is to determine whether HIIT produces superior cardiorespiratory, neuromuscular, biomechanical, and clinical adaptations than conventional continuous moderate intensity training (CMIT) in PD.

The specific research aims are to compare, in PD, the effects of HIIT or CMIT on: 1) maximal exercise capacity; 2) neural and non-neural factors contributing to muscle strength, power and fatigability; 3) biomechanical measures of postural stability and gait; and 4) Clinical markers (Mini-BESTest and Unified Parkinson's Disease Rating Scale (UPDRS)). The investigators hypothesize that, HIIT will produce greater improvements in: 1) exercise capacity; 2) muscle strength, power and reduced fatigability; 3) stability and gait velocity; and 4) clinical markers.

Methods: This pilot project will involve a randomized trial of 30 individuals with PD comparing the effects of HIIT and CMIT. Training will be completed thrice weekly for 10 weeks. Participants will include men and women between 50-85 years of age, who are able to stand unsupported for 1 min, walk 18m without use of an aid, and mount a stationary bike. Participants will be randomized to either HIIT (10, 1-minute cycling intervals at 90% of peak power output, each separated by 1-min at 10% peak power output) or CMIT (30-50min cycling at 60% of peak power output). Participants will undergo the following pre- and post-training assessments: Cardiovascular testing will examine hemodynamic and efferent muscle sympathetic responses to static handgrip exercise and post-exercise circulatory occlusion; Neuromuscular testing will examine muscle activity (electromyography) during voluntary and electrically stimulated contractions of the knee extensors; Biomechanical testing will examine whole-body stability, gait, and balance patterns; and Clinical risk assessments (Mini-BESTest and UPDRS).

Inclusion Criteria:

• Men and women between 45-85 years of age
• Clinical diagnosis of Parkinson disease
• Able to stand unsupported for 1 minute
• Able to walk 18 metres without aid
• Able to mount a stationary bike

Exclusion Criteria:

• History of dementia
• History of stroke
• Type 1 diabetes
• Autonomic neuropathy
• Currently involved in formal exercise training (>3 day per week).

The collection of study outcomes will be completed by individuals blinded to group allocation.