I used to train for years in an old school boxing club. We had a tractor tire and a makeshift heavy wooden club. The idea was to hit the tire as many times as possible, as quickly as you can until you nearly black out. It was meant to build stamina. Then some crossfit faggot probably saw boxers doing that and thought it was meant to grow your lats or whatever. If you used a sledgehammer with force that we were hitting that tire with, it would break after the first use.