Single-Arm Dumbbell Chest Press
Why It Works: Ashley Horner, a trainer for Bodybuilding.com, likes this move because you can’t use your stronger side to help your weaker half out. Working the pecs independently makes us address those imbalances. Plus, the instability of only working one side increases the challenge: “You’re not only working your chest, but you're engaging the stabilizers in the trunk,” Horner says.
How to Do It: Lie back on a bench with a single dumbbell in your right hand. Push the dumbbell up from the chest, then lower back down. Try to avoid letting the dumbbell wobble during the exercise. Repeat all the reps on one side, then switch.