Originally Posted by
genejockey
I do wonder, when you see the TdF guys (and gals)climbing at ridiculous speeds in 40C temps, how it doesn't kill them. I mean, they're probably hydrating as fast as the domestiques can ferry bottles to them from the team car, but still.
Hydration is only part of the story. In the heat, vasodilation in the skin, a huge organ, means that the heart has to perfuse a much larger vascular space. These people just have massive cardiac reserve capacity.
Originally Posted by
big john
If dehydration drives the heart rate up that must affect power?
It drives up the heart rate required to produce a given power. That affects power at the top end of heart output.