Originally Posted by
gregf83
Yep. Your HR was likely higher because you were dehydrated relative to the beginning of the ride. That's one of the reasons HR is often a misleading indicator of power/effort.
+2
Thus if you're doing intervals by HR, you need to adjust the HR you're trying to maintain on the intervals toward the end especially with a hot, long workout.
If your last intervals feel too easy, they probably are,and you need to up your effort, even if it puts you above the targeted HR zone.
In that instance RPE, correlated with experience, can give you an idea of how much higher your HR should be on the final intervals.