An issue that exists if the effect is euphoric enough to, i forget the term, where you become more likely to do risky things or ignore warnings, something to do with inhibition. Anyway, that, can make you totally ignore say, an excessively high heartrate, youd be surprised what pain and vague senses/mood do to ones behaviour, a pulled muscle ruins my day.
Back when i was on methylphenidate id have pleasant manic episodes at night, from my slow release pills, during those episodes i used to exercise since it was very difficult to do during the day, i could barely breathe. I far surpassed my limits and often came very close to passing out, but in a continuous-process sort of way, so id be pushing right up to the threshhold because my body was doing just fine but my brain wasnt keeping up. Now im on dexamphetamine and it doesnt augment my heart rate at all.
Anyway, i spoke to my doctor about this who assured me, its purely a mechanical issue. a high chronic heart rate is bad for your heart, similarly is having it beat too quickly for a short time during exertion, but, its in pretty absolute limits, i.e resting heart rate is fine under 100 or so regardless of what you take/are doing, and during exercise, i think 160 or 180 is just, danger zone and your heart is hurting itself by beating that hard, even if light jogging is causing that. as long as you arent exceeding those physical human limits, you are fine.