Just try hitting a heavy bag for a few minutes and you'll quickly see why boxing counts as cardio. "With boxing, you're constantly shuffling, twisting, keeping your arms up at a high level, and using a lot of speed and coordination to punch," says Iwaniuk, who thinks this, as well as activities like judo and jiu jitsu, are the pinnacle of non-running cardio training. "Any time you repeatedly strike something for a set amount of time, you will work your heart big time." If you're at home without a heavy bag to take it out on, pick up some light weights and shadow box. "It's tough to throw 200 punches with any kind of weight in your hand," says Iwaniuk. "Even two pounders!"
