I was a division one hockey player. If we messed up in practice believe me we skated or did so many pushups our arms shook. Negative association with exercise?? seriously?? The big thing is that when one screwed up, we all suffered the consequences. An individual mistake in a game costs the entire team, so an individual screw up in practice should also cost the entire team. That was my coach's philosophy then and it is my DD's 13U coach's philosophy now, and I couldn't be more supportive. it makes one REALLY not want to let down one's teammates. And no I'm not the coach (our organization does not have parent coaches, but that's another topic). Sometimes you need to grab a team's attention, and a few sprints, crunches, or pushups will do that. And given that we practice 4 hours a day at least 3 days per week, we can afford to lose some "valuable practice time."