Being comfortable and performing up to your optimal potential on the bike starts with a great bike fit, however performance can be enhanced by additional methods as well, like supporting your feet correctly with custom footbeds like eSoles.
Regulation of core body temperature and heart rate are also key components of keeping you comfortable and performing at your best on your bike or your run.
Ever wonder why cyclists in the Tour de France and other long races like Ironman end up pouring more water on their heads and back of their necks than drinking it. Its because they are trying to keep their core temperature under control.
It is well known in endurance sports that elevation of core body temperature ends more athletes dreams than dehydration does.
Just ask Fabian Cancellera, who collapsed in anger at the end of a time trial and tore off his baselayer, claiming that because he picked the wrong baselayer for the day, he overheated, his core temperature rose and lost the race because of it.
Increased core temperature limits performance. which can result in all your hard training efforts being wasted
For a comprehensive article on the subject click this link...
Factors limiting Endurance Performance in the Heat