The key unifying attribute for ME / CFS as a disease seems to be the post exertional malaise (PEM), which seems to have these characteristics: * Quick accumulation of either lactic acid or some other byproduct of aerobic exercise in the muscle, which does not clear sometimes for many days after exercise. * An inability to generate strong muscular contractions after a period of aerobic exercise Some describe this as a lack of stamina, but stamina to me is a vague word that strongly suggests a lack of cardiovascular fitness. In my own case, this is absolutely NOT the reason for the muscular fatigue. My heart and lungs are ready and willing and able to go on. Something very specific to metabolism inside the muscle just completely fails, and no amount of cardiovascular conditioning will change that. More exercise will in fact make the problem worse. My question is are there forms of exercise that work well for CFS / ME? In no particular order: 1) I am finding that weight workouts with fewer than eight reps / eight seconds of activity per set, with long rests between sets, can be tolerated. What about others? If you let yourself start getting out of breath and becoming aerobic, there will be hell to pay the next day. 2) I just started yesterday to test the idea of doing swimming sprints, just single laps followed by 1.5 minute rests per lap. This was only partially successful unfortunately. I ended up having some real muscle soreness, but not the same kind of overwhelming fatigue I would experience if I made the workout fully aerobic. So I am calling this an experiment in progress. I may need to increase the length of rests between sets, and it might also be worth experimenting with slowing down the pace of the sprint after eight seconds. (See more below on that.) This is in order to keep the activity out of aerobic / lactate energy use. 3) Is taking a long slow walk recommended? I guess there is no way to keep this from becoming aerobic, even at a slow pace? Any guidelines that can be shared here are appreciated. This one is very tricky, because a 40 minute walk can give you a lot of endorphins and you feel good, but if you are too far into aerobic zone you are producing the conditions that will leave you exhausted that night and the next few days. In considering the above points, let's use a reference on different types of energy systems: http://www.brianmac.co.uk/energy.htm What is important to take out of this reference: A) We want to stay in the Alactic Energy System. And what is critical here is you get two seconds of ATP storage, and about four to six additional seconds of creatine phosphate use. That gives you eight seconds maximum of activity at high intensity before you start to use aerobic energy. B) Please note in the Alactic Energy section the documentation about how much time you must wait between sets to get recovery of your creatine stores. That is critical in order to have subsequent sets keep you within the Alactic Energy System. So I'm very interested in hearing if any of you are managing to find a way to workout in a way that avoids the horrific muscular side effects of this disease.