anybody who's strapped a helmet on and run down the field for 10 110's knows that the mouthpiece severely impedes breathing and is avoided as much as can be gotten away with. especially when one's sinuses only open halfway.
OMG yes... I hated that thing... then they try to give you the one with the breathing holes in it that covers your whole mouth... like michael irvin... yah I want one of those... stupid mouthpeice...
I always gnawed mine so much that it wasnt padding much. I'd hover back there with the linebackers waiting for the tightend to lineup, gnawing on my mouthpiece and clenching and unclenching my fists... kinda doing the mindset thing like Stalone and his backwards hat in Over the Top