Covid Restrictions have impacted longitudinal assessments for the effect of the intervention

The therapeutic effects of exercise in Parkinson's disease (PD) are commonly reported, however the mechanisms are unknown. The purpose of this study is to investigate the potential mechanisms of exercise in the brain for the treatment of PD.

Positron Emission Tomography will be used to measure dopamine neuron density, endogenous dopamine release and neuroimflammation. We will also use functional magnetic resonance imaging (fMRI) to measure brain activity. Assessments will be conducted before and after a 12-week exercise intervention and 3-year follow-up. Participants will be randomly allocated into either an aerobic or a stretching intervention. Clinical measures of motor function, cognition and mood will also be assessed.

Inclusion Criteria: Diagnosed with Parkinson's Disease, Exercise less than 3x per week.

Exclusion Criteria. Describe which potential participants will be excluded from participation, and list the criteria for their exclusion.

1. atypical Parkinson syndrome (progressive supranuclear palsy, multiple system atrophy, drug-induced etc.);
2. significant osteoporosis or arthritis;
3. other neurological disease/complications (e.g. myopathy, stroke, brain lesion, MS);
4. self-reports claustrophobia;
5. history of cancer within 5 years of study participation;
6. high dose of radiation from other procedures within the year;
7. not able to tolerate being off PD medication for up to 24 hours;
8. a female subject who is breast-feeding or pregnant.
9. Subjects who regularly use anti-inflammatories (only excluded for PBR scans).

Exclusion criteria for MRI scanning and magnetic stimulation from repetitive Transcranial Magnetic Stimulation (rTMS) scanning includes:

1. artificial heart valve;
2. brain aneurysm clip;
3. electrical stimulator for nerves or bones;
4. ear or eye implant;
5. implanted drug infusion pump;
6. coil, catheter, or filter in any blood vessel;
7. orthopedic hardware (artificial joint, plate, screws);
8. other metallic prostheses;
9. shrapnel, bullets, or other metal fragments;
10. surgery or tattoos (including tattooed eyeliner) in the last six weeks;
11. brain surgery
12. have a cardiac pacemaker, wires or defibrillator;
13. have had an injury where a piece of metal lodged in the eye or orbit;
14. have a ferromagnetic aneurysm clip; and
15. have a history of seizures/epilepsy
16. history of severe or uncontrolled headaches/migraines
17. taking medications that lower seizure threshold (e.g. amitryptiline, haloperidol)

Subjects may be excluded following study enrollment if they meet any of the following exclusion criteria:

1. significant cognitive impairment or depression;
2. significant or unstable cardiovascular or respiratory disease - all subjects will undergo a screening exercise bicycle stress test; or
3. failure to comply with the exercise or stretching intervention program by not completing at least 30 of the 36 exercise classes.
4. Severe/multiple head trauma(s)