You might not have known about a sport called box lacrosse.  It's like lacrosse, widely considered the most violent youth sport on record including football and hockey, except it's played inside a hockey rink.  Nets hang from the ceiling and attach to the plexiglass above the boards.  Turf covers the surface area normally frozen with ice.  Kids race up and down the field with fiberglass sticks.  When one kid manages to secure the ball - racquetball-sized, but more dense than a baseball - the others give chase and whack the carrier intermittently with their sticks.  This is legal.

Every once in a while, the ball carrier makes it past the defense and takes a shot.  A heavily-padded goalie blocks most of the target, but sometimes kids wing one past him and the crowd of sports-crazed parents erupts.

In terms of spectator enjoyment, I'd give box lacrosse four stars.  It's fast-moving and predictable, with three 15-minute periods and running time.

In terms of quality of cardiovascular exercise, I'd give box lacrosse five stars.  Shef was quite sweaty at the conclusion of the games.  He also displayed a powerful thirst, and his face remained thoroughly flushed even thirty minutes past the final whistle.

In terms of player safety, I'd give box lacrosse 3 stars.  Concussion and cognitive impairment seem unlikely; however, bruising and breakage seem imminent due to the stick-whacking aspect of the sport.

Overall, I give box lacrosse four stars.  Why not?  It's pretty good.