Where was the BB?
I understand what you mean Bob they are two MMA fighters and not bodybuilders on stage posing, but one of them used bodybuilding to gain more muscle mass then the other fighter and thus as the commentator said as a result was getting more tired due to him having to breath more to feed all that muscle with oxygen.
My point is: do you get less fitter / stamina when you pack on muscle?
Hope this helps.