Right about now you're probably itching to spend less time cooped up in a gym and more time having fun outside. A plyometric routine will boost the efficiency of your sweat session. "These explosive moves give you more bang for your buck; they're intense; and they work several muscles at once," says Kira Stokes, the creator of the Stoked 360 class for Reebok Sports Club/NY in New York City. "Your heart rate stays elevated the entire time you're exercising, so you burn more calories, even after your workout is over." Do the six scorchers on the next page as a circuit twice through for 10 minutes just three days a week. Then go out and play!