More than 200 animal species inflate their chests to intimidate opponents and/or attract mates. For humans, it works just as well—defined pecs convey an aura of physical magnetism. But here's the secret to a treasured chest: You can't transform your front without also working the back. "In addition to strengthening your chest muscles, show the rear deltoids, rhomboids, and lower trapezius some love," says Adam Rosante, a New York City–based personal trainer who designed this routine. "If you target your pecs but ignore the reverse, you'll become lopsided." Your shoulders will slope forward, making your chest appear smaller. Strong back muscles, on the other hand, pull your shoulders backward and down, and as a result, your chest seems to lift. This upper-body plan combines fast, explosive moves with little rest and heavy weights—not body-builder heavy, but a bigger load than you typically lift—to increase muscle mass, which in turn spikes your metabolism. Here's how to get started.

1 / Floor Press (See demonstration above)
Lie face-up on the floor, knees bent, feet flat. Hold a dumbbell in each hand, arms extended above chest, palms facing in. Bend elbows, lowering weights until triceps hit floor. Return to start. Do 10 reps, then immediately do Move 2 to complete set. Do 3 sets.

2 / Bent-Over Rows
Stand with feet hip-width apart, knees bent, and hold a dumbbell in each hand at sides, palms facing in. Hinge forward from hips until chest is almost parallel to the floor. Bend elbows and draw weights up to ribs. Pause, then return to start. Do 10 reps.

3 / Center Push-ups
Get in high-plank position, hands under the center of chest, fingers forward, thumbs touching, and feet together. Bend elbows straight back, lowering chest until it hovers above floor. Pause, then return to start. Do 10 reps, then immediately do Move 4 to complete set. Do 3 sets.

4 / Dumbbell Swing
Stand with feet shoulder-width apart and hold a dumbbell in left hand, arm extended. Bend knees, swinging weight between legs. In one motion, straighten legs and thrust hips forward as you lift weight to shoulder, drawing elbow back. Return to start. Switch sides after 10 reps.

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