This might be true of some people at some intensities but it is not universally true. The more intense my exercise the worse I feel afterwards. @ 70% of max h

This might be true of some people at some intensities but it is not universally true. The more intense my exercise the worse I feel afterwards. @ 70% of max hr I feel pretty good afterward. 80% and I start feeling pretty tired. At 90-95% I get super irritable, nauseous, and can't sleep.