Starting Position: Holding a dumbbell in your right hand, bend over to place your left knee and left hand on a bench to support your body weight. Your left hand should be directly under your shoulder and your knees should be positioned directly under your hips. Engage your abdominal / core muscles stabilize your spine. Your back should be straight and strong and your head aligned with your spine. Pull your shoulder blades down and back. Do not allow your low back to arch. Maintain these engagements throughout the exercise. Straighten your right arm (with the dumbbell) toward the floor. Do not allow your torso to rotate or your shoulder to droop toward the floor.
Upward Movement: Exhale and slowly pull the dumbbell toward your side body. Keep your arm close to the side of your body as you bend your elbow and pull the dumbbell up. Continue pulling the dumbbell upward until you are unable to lift any further without rotating your torso. Do not rotating your body or change the position of your spine throughout the lift.
Downward Movement: Inhale and gently lower the dumbbell to your starting position. Keep the back straight and strong, abdominals engaged and shoulder blades pulling down and back.
Try performing this exercise alongside a mirror to monitor any change in your back or shoulder position and check for trunk rotation.