@Mij Interesting about your immune symptoms. When you had those symptoms, did the same symptoms continue with no break after exertion stopped? My symptoms happen year-round. I do have both allergies and recurring infections, but the PEM symptoms happen regardless of if these two are present or not.
I think one of the differences in my case wrt to PEM, may be due to the fact that my illness is and was from the start, very heavy on the pain, immune and neurological symptoms. My understanding of why what are typically post-exertion symptoms happen for me during exertion has to do with the time duration variance of PEM onset. PEM onset occurs on a time spectrum, with some patients having symptoms immediately after exertion, some 24-48 hours after exertion and some days after exertion. If we are on a spectrum, I'm at one end of the spectrum and patients whose PEM starts days later are at the other end. Sometimes, I do experience classic PEM. More often though, my symptoms start during physical/emotional/mental exertion. The PEM always starts with similar symptoms regardless of whether onset is during or post-activity.
What I wonder is if other patients continue exertion well-beyond the point they should, do their PEM symptoms still wait until afterwards?