Reminds me that a few years ago my wifes grandfather (80+) was wondering if he should cut back on the amount of exercise he was doing. He would regularly be knocking on our door at 6am to see if one of us would want to got for a quick 10k run or to hit the gym.

He was a firefighter in NY in his youth and had never stopped exercising even after retirement.

He went to his GP explained his workout routine and was basically told there is no precedent for it as people his age tend to not be running 10km a day. In short he was told if you're not in pain or fatigued keep at it.

I think he's nearly 90 now and has cut back the running to only a day or so a week, but last time we went to visit he was in his garage bench pressing 50kg