When he'd blow his whistle, the guy at the back had to pass everyone on the outside to take the lead. Everyone had to accomplish this. If he felt we weren't running fast enough, he'd just swallow his whistle and make us keep running.
It was brutal and lots of kids puked from the exertion. If he felt we weren't hustling enough during practice, he'd immediately stop what we were doing and penalize us with this drill. It may have helped conditioning, but most of us thought he was slightly sadistic and a generally mean son of a gun.