"This pilot project will involve a randomized trial of 30 individuals with PD comparing the effects of HIIT [High-Intensity Interval Training] and CMIT [Continuous Moderate Intensity Training]."

"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)."

"Training will be completed thrice weekly for 10 weeks."

So the members of the HIIT group do 1 minute of cycling at 90% of peak power output, "rest" for 1 minute, then do that 9 more times back to back. Given the rather loose eligibility criteria, I think the 90% figure is probably a little ambitious!

Physiological Benefits of High-intensity Interval Training for Individuals With Parkinson's Disease - Full Text View - ClinicalTrials.gov

(hat tip to iqbaliqbal at HU for the link)