Picture some of the most in-shape athletes you’ve ever seen. If you ever watched a boxing match, or even if you just saw some fighters training or working out, you’ll probably conclude that boxers have the sort of fitness levels that you’d like to have. After all, they don’t work out for vanity or to alleviate boredome, they do it because their health and their careers depends on it. If they’re out of shape, they’re going to get knocked out cold.