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 hand should be placed directly under your shoulder and your knees should be positioned directly under your hips. Gently contract your abdominal / core muscles ("bracing") to stiffen your torso and stabilize your spine. Your back should be flat and head aligned with your spine. Depress and retract your scapulae (pull your shoulders down and back) without arching your low back and maintain this shoulder position throughout the exercise. Extend your right arm (holding the dumbbell) towards the floor without allowing your torso to rotate or shoulder to move towards the floor.
Upward Movement: Exhale and slowly pull the dumbbell upwards, bending your elbow and pulling your upper arm backwards. Keep your arm close to the side of your body and continue pulling the dumbbell upwards until you are unable to lift any further without rotating your torso. Avoid rotating your body or changing the position of your spine throughout the lift.
Downward Movement: Inhale and gently lower the dumbbell to your starting position while maintaining a flat back and retracted (pulled back) shoulder position.