Forget about the "fat-burning zone," that low-effort no-man's-land where your body supposedly uses flab for fuel. It's bunk, says Robert dos Remedios, C.S.C.S., head strength and conditioning coach at California's College of the Canyons. "The key to shedding pounds is increasing workout intensity," says Coach Dos, who created the two "complexes" on this page. "Doing exercises back-to-back at maximum effort revs your metabolism for up to 36 hours." Fitness experts call it the afterburn effect; you can just call it smart training (Your diet plays a big role, too, check out five easy ways to rev up your metabolism)
More: 5 Tips to Speed Up Your Metabolism
A stopwatch and a pair of Valslides ($35, performbetter.com) or, in a pinch, two paper plates.
Start with Complex A, performing 10 reps of each move as quickly as you can without pausing between exercises. Rest for the same length of time it took you to do the complex. Repeat two more times, rest 3 minutes, and follow the same process for Complex B. If you're short on time, try the 90-second ab blaster instead.
More: Sculpt Sexy Abs in 15 Minutes
1. Explosive Pushup
Assume a pushup position with your hands slightly beyond shoulder width and your body in a straight line from head to ankles. Bend your elbows and lower your body until your chest nearly touches the floor; then push up with enough force that your hands leave the floor.
2. Jump Squat
Stand with your hands on the back of your head and your feet shoulder-width apart. Lower your body until your thighs are parallel to the floor, and then jump as high as you can. When you land, immediately squat and jump again.
More: How to Master the Squat
3. Sumo Squat Thrust
Stand with your feet slightly beyond shoulder width, and then squat and place your hands on the floor in front of you. Kick your legs back into a pushup position, and quickly return to the squatting position. Stand and repeat.
1. Spiderman Pushup
Assume a standard pushup position but with your palms on the Valslides As you lower your body, slide your left palm along the floor in front of you, lift your right foot, and swing your right leg out sideways. Try to touch your right knee to your right elbow. Return to the starting position and repeat with your right arm and left leg. That's one rep.
2. Mountain Climber
Assume a pushup position with your arms straight and your toes on the Valslides. Bring your left knee toward your chest by sliding your left toes forward. Return to the starting position. Repeat with your right knee. That's one rep.
More: Your 7-Day Stair-Climbing Workout
Assume a pushup position but with your weight resting on your forearms and your feet on the Valslides. Brace your abs, squeeze your glutes, and push back with your upper arms. (You'll feel your core engage as your feet slide backward.) Return to the starting position and repeat.
Looking to emerge from hibernation and transform your body for summer? Check out these four ways to shed the bear belly.
Increase your metabolism and tone up faster. Find a fat-burning class.