Barker’s onto something here:
It seems the body has a governor of sorts that tells you how much gas you have left in the tank and doles out discomfort when it thinks you’re working too hard… Some people can ignore it. Those people run ultra-marathons and multi-state cycling races that last days. Their bodies aren’t all that different than yours or mine. So, no, you don’t get to look at them and say they are physically gifted freaks of nature. It seems the majority of what allows them to do what they do is mental.
The human mind is a lying machine.
Not Unreasonable 