Do the rear delts, aka posterior delts, belong to the shoulders or to the back? A logical question, which is important when putting together your training program.

ANATOMY

Logical, because the anatomy is confusing here. Anatomically, the rear delts, a.k.a. posterior deltoids, are part of the deltoids (the shoulder muscles). But because they are located at the back of your shoulder joint, they look more like a back muscle.

The primary function of the rear delts is horizontal shoulder abduction (the reverse fly movement). As a result, they play a much larger role in pulling exercises like pull-ups and rows than in traditional overhead shoulder exercises. The rear delts are therefore primarily an auxiliary muscle in most back exercises.

DIRECT TRAINING

Some see this as a good argument for not specifically training the muscle. But the same argument could be used for not training your biceps directly. By not training the rear delts directly, your shoulders may lack thickness in the side view.

A complete shoulder development, so of all three heads (front, middle and back) is also important to become stronger in the basic exercises for both back and chest. But also for injury prevention, because with strong back shoulders you prevent an imbalance in the shoulder joint.

In short, make sure the rear delts don’t become a weak link.

PROGRAMMING

Should you train your rear delts for your back or shoulders, assuming you have a split routine with pulls (back) and pushes (chest/shoulders)? Our advice: train them for your back.

Hit them with the big pull exercises and finish the job with the reverse fly and one or two of these specific rear delts exercises.

If you train full body, do a maximum of one isolation exercise for the rear delts per workout.