I ask because every time I overexert, be it physical activity or mental stimulation, it damages my brain further and every time so far this damage has been permanent. I don't just get increased brain fog or things like that- I can literally feel parts of my brain shutting down and so far they have never come back on even slightly. After a SPECT it was speculated that I have widespread mitochondrial damage in my brain. So what is the biomechanical process of overexertion? Is this something that is even known? And what changes once that happens? Why is it that (for me, so far) once you have damaged certain cells from overexertion they don't recover at all. Is overexertion commonly permanent damage to cells or nerves?