Boxing - Start with feet hip-width apart, a 3- to 5-pound dumbbell in each hand. Bend knees and lean forward from hips, pulling belly in tight. Bend arms, bringing elbows close to rib cage, palms facing in. Extend right arm in front, palm down, and left arm behind, palm up (as shown). Return to start; switch arms to finish one rep. Do 20 reps. Works abs and arms.