 Side bends. Stand with your feet wide apart, both hands at your sides, and hold a dumbbell in one hand only. Making sure to keep both of your knees locked straight, bend your torso directly to the side on which the dumbbell is held, until the weight is level with your knee joint. Then, slowly bring your body back to the erect position. Reps 15 to 20 per side. Notes, best done with Dumbbell.