I'm wondering about subsets of ME/CFS regarding the greatly reduced stamina that might be due to reduced ATP production. I don't seem to suffer from that, and I'm wondering if that's a rare subset or not. By greatly reduced stamina, I mean that a simple physical activity causes your muscles to 'run out of energy' in minutes, the way a healthy person's would feel after hours of that activity. This doesn't include the lack of desire to do the activity due to low mental energy, or due to pain; it's a matter of ATP depletion or lactic acid build-up. I added the severity categories to see if anything interesting showed up regarding that.