With dumbbell in one hand, lie chest down on elevated bench. Position palm forward (thumb up) with elbow straight or slightly bent.
Raise upper arm to side until elbow is shoulder height. Maintain upper arms perpendicular to torso with elbow straight throughout exercise. Maintain palm forward position. Lower and repeat.
Bench should be horizontal and be high enough to prevent dumbbell from touching floor. Upper arm should travel in perpendicular path to torso to minimize latissimus dorsi involvement. Bench should be high enough to prevent dumbbells from hitting floor and close to horizontal. Lying at 45° is not sufficient angle to target rear deltoids. This exercise AKA "prone full can" has been suggested to exercise supraspinatus muscle in rehabilitation settings (Blackburn TA, et al. 1990; Reinold MM, et al. 2007).