Seated Dumbbell Lateral Raise

The seated dumbbell lateral raise isolates the lateral deltoid, the part of the shoulder that gives it width, and sitting is what makes the isolation real. Standing, it is almost impossible not to use a small dip and drive of the legs to start each repetition, and that momentum carries the dumbbells through the hardest part of the range. With your back against a bench and your feet planted, the only thing that can raise the weight is the shoulder itself. Expect to use noticeably lighter dumbbells than you would standing, and expect the exercise to feel harder for it. Raise the arms to shoulder height and no further, since going higher hands the work to the trapezius, and lower under control rather than letting the weight drop, because the lowering phase is where most of the stimulus lives.