First of all, exercise produces endorphines in the brain, which is very good for moral and to keep away depression.
This is actually not true for me. I have never once in my life experienced an "endorphine rush" from running or other aerobic or anaerobic exercise. Not once. I was convinced that the endorphin rush thing was made up until I understood that others do genuinely experience it, I just don't. Perhaps my receptors are fried, I don't know. This would explain why taking LDN for me was like taking sugar pills.
I have also learned that exercise exacerbates my depression. I read countless articles about how good exercise was supposed to be for mood and depression. However, after more times than I can count, I discovered that if I'm feeling at all negative or depressed, if I take a 20 minute walk, but the end I will be in a bottomless pit of despair or raging and so irritable that no one can come near me for the rest of the day. So while this may be a 'cure' for some, for me it is like poison.
I believe that exercise (or general physical activity) is really important, so don't get me wrong, I'm not saying that avoiding it should be everyone's purpose. But when it comes to CFS/ME, it seems like it is often actually counterproductive. I do agree with you that it can look different for everyone depending on their disability levels, and perhaps what you are thinking of as 'exercise' is really just some general movement that others wouldn't label as 'exercise'. Maybe this is what is causing the confusion?
Exercising also produces new motochondria, which help in the energy production cycle.
I think this is something that could possibly hold true as a general rule for healthy people. One of the hypothesis of CFS/ME is that mitochondria aren't produced the way they should be.
I don't doubt that movement/exercise is important for the spine, for relieving posture and general blood/lymph flow. But I haven't heard of a single person on this forum who had an increase in energy as a result of exercise.
I agree with
@Valentijn that for me, the choice is to either: (1) do some strength training at the gym and then be completely unable to do anything for the rest of the day and possibly days afterward, or (2) not go to the gym but be able to go grocery shopping, cook some meals, do a little laundry, and generally take care of myself.
For the longest time, I prioritized the gym because I thought exercise was really important. Now I'm seeing that I need to be more selective with how I expend my energy, because that energy is NOT getting replenished anytime soon.
Exercising will also help keeping a minimal muscle mass, which will in return help you with keeping a stable upright posture, avoid falling, lifting objects when you have to, ect.
Raising and lowering your arms a few times is not going to preserve muscle mass. I agree that if a person can do a small amount of movement, then that is better than no movement. But in order to maintain muscle mass, have a good posture, avoid falling, etc... you need to do specific exercises on a regular basis to specifically target those things, and those exercises are not easy if you are ill. I know because I'm currently doing them!
I've had horrible balance and weak ankles my whole life, even though for most of my life I was an avid walker. It's only by doing a specific program designed by my chiropractor (walking lunges, balance board, etc...) that I'm slowly strengthening my wobbly ankles and improving my balance. I had to modify the exercises I was given because I couldn't tolerate what would be fine for a 'normal' person to do, and after getting several weeks of really intense muscle spasms that left me in pain and soreness, I had to suspend everything and now I'm back to square one.
I still think it's worth it for me, since (1) I've seen improvement as a result of doing these exercises, and (2) as long as I'm careful, I can usually tolerate them. However, for someone who is more limited than me, I think the focus should be using whatever energy/ability to move is available to perform self-care tasks, which will double as being 'exercise' because they will involve movement of some kind.
I don't want you to feel like I'm attacking you, I think we may be all loosely saying the same thing with different words.