Lean forward from your waist until your chest is resting on your thighs. Let your arms hang down on either side of the bench, keeping a slight bend in your elbows. Raise both dumbbells to the side in a wide arc until they are level with your shoulders, while keeping your elbows slightly bent. Pause for a moment at the top of the movement, then slowly lower the weights back down to the starting position. Repeat this movement for the desired number of repetitions.