Posterior (rear) delts serve to figuratively and literally round out shoulder development. They are essential not only for proper arm symmetry and balance but also for back symmetry. Frequently, rear delts are underdeveloped because they are not visible when you throw up a biceps pose. Sounds silly, but it’s true. Most back movements will engage the rear delts to some degree, but to really zero in on them there is no better exercise than side-lying rear-delt raises. Lie down on your side on a bench. Stabilize yourself by allowing your bottom foot to drop to the floor in front and support your head with your bottom arm. Start with your arm hanging down toward the floor at about chest level. Keeping the arm stiff but slightly bent, raise the weight out in front of you, leading with your elbow (pinkie up). Raise your arm until your elbow is not quite pointing to the ceiling. Stop before you feel the resistance decreasing. The point of this exercise is to make it burn!
ALTERNATIVES
Bentover rear-delt raises using low cable, bentover rear-delt raises with dumbbell.
WHEN TO FOCUS ON REAR DELTS
Rear delts are a good finisher for back. They can also be used as part of a giant set with one-arm dumbbell rows.
FORM AND FUNCTION
The origin is along the lower lip of the posterior border of the spine of the scapula. Its insertion is on the lateral side of the humerus at the deltoid tuberosity. The posterior deltoid extends the shoulder and externally rotates the arm.
