You by mechanics wouldn't make it to the first check.  Your Rage ending, would just sending you collapsing in fatigue.  Under normal conditions someone can run for X rounds, where X is equal to their CON score.  However, trying to run while in a state of Rage, will be fine...if your Rage lasted as long or longer than you could normally run, but mechanically that's not possible.<br/><br/>Now at 17th level, a barbarian could continue to run after his Rage...or attempt to, because he is no longer fatigued after ending his rage.