I used to run with this guy when he was at Radford and he's kind of a weird guy. Somehow this dude has a max heart rate of 256 and I've been with him when he hit it multiple times. Every time he ran himself into the ground to the point where he can't stand at the end of the workout (it's kind of scary to be honest).
His "mantra" is that he runs to enjoy it and push his physical limits. He's just not into racing for some reason which I don't know why but he does do time trials all the time. He asked me to time him (record his splits) one day when he did a 10k time trial and it was just insane. The guy ran a mid 28 and collapsed after he crossed the line. He just laid there for a few minutes and then got up like nothing had happened.