You've probably read about football players collapsing during pre-season practices in recent years. Of all of the major sports, football is perhaps the most reliant on conditioning, considering that the interior linemen on both sides of the ball average anywhere from 275-350 pounds.
Bearing this in mind, Where's Huddles? offers a cautionary tale on athletic conditioning in "A Weighty Problem":
Didn't see this one the first time. No rating.