I’ll go out on a clinical limb here and say that for anyone with adequate coronary circulation and no history of an unstable arrhythmia, irrespective of age, short intervals of maximal exertion carry no risk of acute harm. Personally, I run the tach into the 170s once or twice a week, ‘cause it feels so good (bad).

I was in a race a few years ago where an old guy dropped dead from a cardiac arrest, but it was sailboat race to Bermuda and the poor man crumped in the cockpit on the first night.