I do plenty of training for the level of fitness that I think I need to be at at this point in time (I'll do more as i try to increase it). I think you do need to be fit, but if you ignore the fact that your tired you can still perform as well, if not better in my experience, and then have a break at the next subbing opportunity and do it all over again next time.

__________________
I\'ll think of one later...