High-intensity interval training (a.k.a., HIIT) is a triple threat: “It’s quick, easy, and effective,” says Angela Gargano, a certified trainer and creator of Strong Feels Good & Pull-up Revolution.

High-intensity interval training, or HIIT, is a great way to torch calories, boost your metabolism and get a great workout in a shorter amount of time. And if you're a fan of hopping on the treadmill ...