Triathletes are a odd group to base this on. In any case, the exact age isn&#x27;t important and you would of course expect this to vary dramatically. The point was that it is very far from being as simple as &quot;performance decreases as you age&quot;.<p>But you are correct to point out that your parent is very far off the mark. Max HR is not a useful predictor of performance, and you can not calculate it with a formula. What you want is a test to exhaustion to determine it, but these are highly dubious due to the psychological aspect, and at the end of it you might have a correct value for max HR, only to realize that it is pretty useless for any prediction purpose.<p>Case in point, Chris Froome, winner of the Tour de France in 2015, has a max HR of around 170, yet he can sustain 450W for a hour. Meanwhile plenty of people with a max HR of 200 and beyond can&#x27;t climb stairs without heavy breathing.