Bent-over barbell reverse raise. An isolation exercise. Target muscle: Posterior Deltoid. Synergists: Latissimus Dorsi, Teres Major, Lower (Sternal) Pectoralis Major, and Triceps Brachii (long head only). NOTE: The synergists are involved only up to the point of where your upper arms are directly by the side of your body. Beyond that point (shoulder hyperextension), only your posterior deltoid is involved.