So can anyone tell me or provide a good link to what happens to your heart rate response over time on a ride. For instance. Yesterday I did 4 seperate climbs. On the first climb I hit my peak HR but it's not the hardest climb. So on the 2nd climb, which really hurt, my HR did not rise as much, 3 or 4 beeats lower. Likewise on the third and fourth, in fact the max HR dropped on each. So out of curiosity, rather than any real need to train for racing or owt, what's happening there. Does the heart tire? Or is it that despite how it feels, my legs are actually too tired to push as hard as I get further into the ride so I don't need as much oxygen? Just interested.