Want to rev up your metabolism? Trade your time on the treadmill for a little metabolic conditioning! Research shows this whole-body, high-intensity, interval-style training is just as effective at boosting aerobic fitness as a longer cardio session and more effective at improving muscular endurance and increasing metabolism. Plus, study subjects who did metabolic conditioning perceived their workouts as more enjoyable and were more likely to stick with it, compared to those who ran on the treadmill for 30 minutes.

This 20-minute routine combines the cardio benefits of this type of training with metabolically active-muscle building moves for a doubly challenging workout.

How it works: Do 1 set of each exercise back to back. After you complete the last move in the circuit, rest 2 to 3 minutes before repeating one more time (the full workout should take you 20 minutes or less). For best results, do this routine four nonconsecutive days a week—no additional cardio needed! (A flexibility or foam rolling routine on your off-days is a great compliment to this plan).

You'll need: A set of heavy dumbbells. Choose a weight that allows you to complete the prescribed number of reps, nothing more, with good form.

Begin in a split stance with right leg forward, left heel lifted, holding dumbbells in front of shoulders, elbows bent in by sides, palms facing in. Lower into a split squat, bending knees and pushing hips back, as arms extend overhead. Press back up, bending elbows and lifting left knee up toward chest, balancing on right leg for 1 count. Return to start. Do 10 reps, and then repeat on opposite side.

Begin in a lunge with right leg forward, left arm extended overhead (palm facing in) and right arm down by side. Jump straight up, switching arms and legs midair, landing in a lunge with left leg forward and right arm extended overhead. Repeat as quickly as possible for 30 seconds. Rest for 10 seconds before repeating.

Begin in a straight-arm plank with hands shoulder-width apart. Bend elbows in by sides and lower torso towards floor, keeping body in a straight line as you lower. As you press back up, extend right arm out straight in front of shoulder with palm facing in, lifting left leg up behind hip, pointing toes, and hold for 1 count. Return to start. That's one rep. Do 10 reps total, alternating arms and legs each time.

Lower into a squat with arms extended out to sides of shoulders, palms facing up. Jump up, bringing legs and arms together, clapping hands in midair. Land in starting squat position. Repeat as quickly as possible for 30 seconds. Rest for 10 seconds before repeating.

Lie on your right side with right forearm on the ground angled front and left hand behind head. Your hips should be stacked, right knee bent under left. Keep abs engaged and think of pressing the right side of your ribcage away from the floor. Press down through right palm and extend left arm. Keeping left arm extended, lift hips off the floor and extend right leg, crossing it behind left into a full side plank, reaching left arm to ceiling and looking up to hand. Hold for 1 count, and then gently lower back to starting position. Do 15 reps on one side before repeating on opposite side.

Stack dumbbells about 1 foot in front of you on the floor. Perform a squat thrust by lowering into a squat, quickly placing hands on the floor, and jumping legs out into full plank position.

Jump legs back into squat and immediately lift hands off the floor and jump up and over the dumbbells, bending knees, tucking heels into body, and swinging arms in front of chest to help you jump higher. Land on the other side of the dumbbells and repeat squat thrust.

Repeat as quickly as possible, jumping back and forth over dumbbells, for 30 seconds. Rest for 10 seconds before repeating.

Grab a pair of dumbbells and lie faceup, holding the weights above chest with arms extended, palms facing in. Your feet should be hip-width apart, heels lifted. Bend elbows in by sides, palms facing in, pressing them down into the floor as hips lift up into bridge, keeping heels lifted. Return to start. Do 15 reps.

Begin in a full plank position. Start doing a traditional mountain climber by "running" knees into chest and start to "crawl" forward by "walking" left hand forward and then right. Repeat as quickly as possible for 30 seconds. Rest for 10 seconds before repeating.