I know that fitter people have lower resting heart rates but what about while they are exercising?
My guess is that because it is 'better' the heart can now achieve more beats per minute and so the max heart rate while exercising would increase.
And exercise the same as before would have a lower heart rate? (eg. running 1 km in 5 minutes while unfit would have a avg heart rate of say 150, while doing the same thing after getting fitter the avg heart rate would now be 120).
Would putting in the same effort during an exercise have higher or lower heart rates after getting fitter?