It would be good to have more data on this. If it’s true for a lot of people it tells you something about what PEM actually is. When you exert past a certain point the body shifts how it’s functioning, metabolic state, immune recruitment, whatever the mechanism is. Say that shift is the PEM trigger, and where it sits is set by your baseline. Then there’s two ways PEM could work. Option 1. Going into state 2 releases something, call it X. X kicks off a cascade with its own shelf life, e.g. 4 days. State 2 itself isn’t sticky, drop your exertion and you’re back in state 1. So what you’re feeling is X doing its thing, not the state you’re in. Your exertional function is back to baseline, you just feel terrible because a process got started. Resting doesn’t shorten it because the thing you’d be resting isn’t what’s driving the symptoms anymore. All rest does is stop you releasing X again. That’s the sunburn version. Option 2. PEM is state 2. You drift out of it rather than switch out, symptoms follow that drift, and how fast depends on how little you do. Your exertional function is actually changed for the whole crash and rest works directly. So basically: does exertion start a separate process, or is your exertional function itself different until PEM calms down.