Hold a pair of 3- to 5-pound dumbbells at shoulder height with arms bent, palms facing in. In a slow, controlled motion, punch your right hand diagonally across your body to the left, keeping it at shoulder level. Allow your torso to rotate slightly as you punch, but keep your lower body still throughout the move. If you feel the move in your shoulder rather than your chest and back, slow down; you should feel your chest and upper back muscles flex and contract. Return to start, and alternate for 20 total reps―10 on each arm. Do 3 sets.