In this variation, the abs work extra to maintain stability as you pull the dumbbell away from your center. Begin sitting with your heels planted about two feet from your butt, holding the weights at chest level with a slight bend in your elbows. Lean back a few inches, pulling your abs toward your spine. Keeping the left arm still, open your right arm to the side, making sure the weight doesn't go beyond your shoulder. Bring your right arm back to center to complete one rep. Complete 10 ...