What percentage of UFC fighters...

[DeathByBeer]

.....and does this mean that Olympic swimmers also make great MMA fighers?

 

[Reveen]

Lower body temperature

 

[LostMyBlackBelt]

I think a lot of people do it as a courtesy to their training partners. I've grappled with some hair dudes before and the first time you take a hair, sweaty man chest to the face you understand why they'd shave.

Taking a sweaty shaved man chest to the face is not great either, put a shirt on.