Could you post the safe way to exercise here as I dont want to join facebook.
Or alternatively, could other PR members highlight the important bits.
I may try buying a heart rate Monitor...i dont know.
I'm not sure why lartista doesn't want to share information, but you can find some of it by reading up on the work of the folks at Workwell Institute and Connie Sol at Dr Klimas' Institute of Neuroimmune Medicine.
First and foremost, you need to know
your anaerobic threshold. This is something that needs to be tested. Standard formulas that apply to healthy people DO NOT apply to us and can be dangerous. You need to have a CPET test, preferably one done by someone familiar with ME/CFS so they don't massively crash you. There's some question as to whether a 2-day CPET gives a more appropriate AT than a single CPET.
Once you know the heart rate at which you enter the higher anaerobic metabolism (your anaerobic threshold or AT), you keep your everyday activity some amount below that and your limited exercise (1-3 minutes at a time) just below your AT.
By exercising in 1-2 minute sessions followed by 5-10 minutes of supine rest several times a day (the appropriate length of exercise varies somewhat from person to person), it is thought that you can improve your
lower level anaerobic metabolism (to a degree) so it can compensate for some of the failure of aerobic metabolism.
I have heard that one (or more) of the exercise physiologists has provided a rough guess formula for estimating a safe AT for PWME who don't have access to CPET testing. My vague memory is that it was something like (220-age) x 0.60, but I wouldn't rely on my memory.
You could probably search PR for it. Be cautious if you use it, though, because it is a very broad generalization that may not apply to all PWME, especially those at the more severe end of the spectrum.