When does an act in a sporting event cross the line and become a criminal act?

When does an act in a sporting event cross the line and become a criminal act? Is there a difference whether it occurs during a high school, college, or professional competition? Why or why not? Why is a fight in a hockey game essentially condoned (usually resulting in a mere five-minute penalty) where the same act, even if consented to, subjects the combatants to a crime of mutual combat?