Maxperson
Morkus from Orkus
In weightlifting in particular, being able to fire yourself up and draw upon deep reserves of stamina and willpower is very, very, very important and pretty much critical to success. In martial arts, going all-out 100% of the time isn't going to do anything other than tiring yourself out.
That's not a second wind, though. Read the link above. There are different methods you use when being physical. Focusing willpower to go beyond your normal stamina limit is not the same as a second wind kicking in.