How to train your delts?

There are namely three parts of the deltoid (shoulder) – the anterior (front), medial (middle), and posterior (back) head of the shoulder. Many people use completely unbalanced shoulder programs. Studies have shown that seasoned bodybuilders have front delts that are at least five times bigger than sedentary people. But their medial delts are just 3 times bigger and their rear delts are merely 10-15 percent bigger. This isn't surprising, given that many people do unbalanced shoulder training and focus on horizontal and vertical pressing on top of shoulder work. This is partly due to the misconception that side raises are a good isolation exercise for the medial deltoid. Before a modification, they’re not. These studies were done on sedentary people, so athletes with dominant front deltoids can expect even worse results.

In a side raise, taking the force generated by the medial deltoid as 100%, anterior deltoid force is approximately 75% and supraspinatus force is 25%. This means that the supraspinatus (a rotator cuff muscle) and the anterior deltoid together produce as much force as the prime mover, the medial deltoid. The same holds true for overhead pressing movements. Doing them behind the neck or with dumbbells helps a bit, but they still don't produce balanced shoulder development by themselves.

So how to train the medial delts without involving the anterior?

You should decrease the amount of shoulder flexion (raising your arm as in a front raise). The same goes for not fully extending the elbow. Yes, it's easier on the elbow joint, but you should still aim for 99% extension. This should be sufficient to keep the stress on the muscles instead of the elbow. It's better to do the exercise on an incline bench. Try an angle between 15 and 60° incline. The lower the angle, the more you also involve the posterior deltoid. Doing side raises on an incline brings me to another factor to increase medial deltoid activity, range of motion. The first 30 or so degrees of abduction are produced primarily by the supraspinatus, after which the medial deltoid becomes the prime mover. Now, that's not a bad thing, because the supraspinatus needs training as well, but it means that you need to control the motion at the top.

If you're one of those guys that throw the weight to the side in a dancing motion and then duck under it, you're just straining your supraspinatus and hardly working your medial delts. If you use an incline bench, you can't duck under it, and can focus on muscle activity instead. Another very important factor that determines shoulder muscle activation is that the more you internally rotate your shoulder during shoulder flexion and abduction, the more you involve both the medial and the posterior head while minimizing the involvement of the anterior head. However, in a reverse fly, externally rotating your arm actually increases medial deltoid activation at the expense of the posterior deltoid.

So, for middle and rear deltoid training, I’d advise you to extend your elbow very close to fully, not using the scapular plane, and internally rotating your shoulder. These technique adjustments increase middle delt stimulation, but also increase impingement risk. So, I do caution restraint if you have shoulder issues. Also, you can counter these problems by retracting your scapulae. Shoulder impingement is mainly a concern if your shoulders aren't structurally balanced to begin with and these exercises aggravate that situation. Additionally, I recommend doing shoulder isolation work on an incline, which is generally easier on the shoulder.

For the posterior delts, besides internally rotating the shoulders during reverse flys or low incline side raises, you can train them with any type of pulling motion, such as rows or face-pulls. These exercises hyperextend the shoulder (bring the elbow behind the body). The lats and pecs can't extend the shoulder beyond anatomical position, so the posterior deltoids then become the prime movers.

For front delts, the front raise in the scapular plane with the shoulder externally rotated is a good, risk-free exercise. Unless you're not doing any shoulder presses, you don’t need any front delt isolation work, especially not until your shoulders are structurally balanced. Speaking of structural balance, to train the external rotators, do face-pulls with an underhand grip. Squeeze hard at the top and pull the rope all the way against your face. If you want to isolate the infraspinatus and teres minor, do side-lying external rotations. But remember, reverse flys also train all the external rotators, so unless you have trouble activating the infraspinatus and the teres minor, it's generally sufficient to just do those and face-pulls.

As for reps, all delt muscles are actively involved in maintaining posture and stabilizing the shoulder during practically every upper body movement. As such, they can be expected to have a high work capacity and are correspondingly around 60% slow-twitch dominant. This goes for the entire shoulder girdle, with one curious exception – the infraspinatus provides some oomph for the external rotators and is fast twitch dominant by a small margin. So, a rep-range of 15-25 reps is recommended.

Kshitij Vashisth
Fitविज्ञान

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