
I think many people with my level of severity would be okay doing 8 minutes of cycling. The large numbers of people who have done the two day CPET tests in the limited places where those tests are offered are proof of that. But sure, these studies are recruiting people with a certain level of severity, bad enough that they are willing to make a substantial effort to understand their illness better, but mild enough that they can do the task and don't expect to be permanently disabled by it.