Heart Rate Is Not What People Should Focus on to Measure Their Intensity?

i can't recall ever working out with a high level cross food athlete, or an athlete, and any discipline for that matter, were they like, heart rate is the thing i really want to focus on. They just, you know, i don't know too many people that that put a primacy on it. Quite a common but i bet, i bet more peoplear are in agreement. So here's the final question. If heart rat is not what people should focus on to measure their intensity, what should they focus on to measured their intensity? Great question. Oh, i'll wrap it up with this, cause i don't exactly much more to say about it, yes.