Rotator Cuff Muscles – Shoulder Stabilizers


Rotator Cuff Muscles – Shoulder Stabilizers

Your rotator cuff muscles are a network of four muscles that attach your shoulder blade to your shoulder joint. It is clear that these small protective muscles play a maintenance role. This is due to the fact that they surround the shoulder joint and hold it in place. In addition, rotator cuff muscles allow the arms to rotate into various positions. Furthermore, they provide both structural stability and the ability to produce powerful forehand, backhand, and serving movements.

Understanding the importance of anatomy will help you learn which  muscles do what and which exercises train them most effectively! In this post you find out everything you have to know about the anatomy of the rotator cuff muscles.

What are the muscles of the rotator cuff?

The muscles of the rotator cuff are:

  • Supraspinatus
  • Infraspinatus
  • Teres minor
  • Subscapularis

Clever readers will note that if you take the first letter of each muscle name and put them all together, they will actually spell out the word “SITS”. This little trick will help you to remember them all easily.

While your rotator cuff muscles are activated in just about every upper-body exercise (they contract to help stabilize your shoulder joint) they also need to be worked directly with shoulder rotation exercises.

Muscles of the rotator cuff - front & back view

Muscles of the rotator cuff – front & back view

Origin and insertion

Each of the four small rotator cuff muscles originates from a distinct point on the scapula (shoulder blade) and pass across the shoulder joint to attach (insert) on the upper portion of the humerus bone on either side.

Bones & joints of the shoulder

Bones & joints of the shoulder

Can we see them externally?

No. The infraspinatus is the only rotator cuff muscle that’s externally visible. It lies in a triangle between your rear deltoid, teres major, and trapezius. Other muscles of the rotator cuff are not visible.

The teres minor lies above the teres major but isn’t visually distinct from the infraspinatus – it appears to be all the same muscle.

Main functions of the rotator cuff muscles

As already mentioned, muscles of the rotator cuff allow the arms to rotate into various positions.

Rotating your arm backward, called external shoulder rotation, uses the teres minor and infraspinatus muscles. Rotating your arm forward, called internal shoulder rotation, involves the subscapularis muscles. Keeping the arm within the structure of the shoulder joint is the primary function of the supraspinatus muscle.

They also reinforce ligaments and are continuous with joint capsules to help stabilize glenohumeral joint – they run from the scapula to the humerus!

Meet the muscles of the rotator cuff

Supraspinatus muscle

The supraspinatus arises from the medial two-thirds of the supraspinatus fossa on the scapula and inserts into the greater tubercle of the humerus. Its main function is to assist in abducting the humerus and to hold the head of the humerus in the glenoid fossa. To put in simply, it helps you to bring your arm out to the side.

Infraspinatus and teres minor

As you can see, they sit right next to each other on the back of the shoulder blade. Because they both lie at the same angle and attach to the same area of the upper arm bone, they share the same job.

Infraspinatus muscle

Of the four muscles, the infraspinatus is both the most used and the most fragile. This is why you must reinforce it by working in a specific manner. The infraspinatus arises from the posterior medial surface of the scapula below the spine of the scapula, and it inserts into the greater tuberosity of the humerus and the shoulder joint capsule. Its main action is to externally rotate the arm, along with the teres minor. It assists in stabilizing the head of the humerus in the glenoid cavity while the arm is elevated; the superior fibers aid in abduction, and the inferior fibers in adduction.

Teres minor

The teres minor arises from the axillary border of the scapula on the dorsal surface, and it inserts into the inferior aspect of the greater tuberosity of the humerus. Its main action is to externally rotate the arm, along with the infraspinatus. External rotation occurs when you rotate you arm and shoulder away from your body. It assists in stabilizing the head of the humerus in the glenoid cavity while the arm is elevated.

Subscapularis muscle

This is the biggest and strongest of all the rotator cuff muscles located on the front of the shoulder blade. The subscapularis muscle arises from the inner surface of the scapula and inserts on the anterior humerus at the lesser tubercle and inferior shoulder capsule. Like the teres minor and infraspinatus muscle, the subscapularis also helps you rotate your arm and shoulder around. However, instead of rotating them away from the body, the subscapularis is responsible for the exact oposite motion – rotating you arm and shoulder towards the body, a motion known as internal rotation.  It also stabilizes the humeral head in the glenoid cavity during arm abduction.

Rotator cuff muscles: origin, insertion, and function

Rotator cuff muscles: origin, insertion, and function

Target Training

The good news is that these four relatively small muscles respond well to strength training. The bad news
is that most people do not perform specific exercises for the rotator cuff muscles.

Even though the shoulder rotator muscles contract during chest, shoulder, and back exercises, they must be isolated separately in order to be strengthened. They are so involved in stabilizing the shoulders during other upper body exercises that conditioning them is vital.

A well-designed strength training program should include at least one workout per week for the shoulder rotator muscles.

Overloading them with heavy weights when doing chest and shoulder presses and pull-downs and rows for the back can lead to tearing of these relatively tiny muscles if they are not properly strengthened.

Training the rotator cuff muscles isn’t about enhancing their appearance – it’s about preventing injury. Therefore, internal and external shoulder rotations probably won’t win you any bodybuilding contests, but they will help keep your shoulders in good health. Muscle tears in the rotator cuff require surgery and months of time away from the gym.

Exercise for the infraspinatus muscle

The infraspinatus exercise is best performed with a pulley system since there will be tension at the bottom and top of the exercise. The second best would be tubing since it has little tension at the bottom, but maximum tension at the top. The dumbbell version is the most popular, but least preferred. This is because there is maximum tension on the bottom of the exercise and decreases sub­stantially once the arm approaches perpendicular and gravity takes over. The tension is now vertical instead of horizontal, thus decreasing the amount of stress on the infraspinatus muscle.

Exercise for the subscapularis muscle

The subscapularis exercise is best performed with a pulley system rather than tubing or dumbbells since there will be tension at the bottom and top of the exercise. An advanced version of the exercise, the cable comes from the front at a 45-degree angle, and the humerus internally rotates until the palm faces downward; then the person brings the whole arm backward until it is behind the body. This works the subscapulars through a full range of motion.

Exercise for the teres minor muscle

The teres minor exercise works well with a pulley system or tubing, or it can be done with a dumbbell while the person lies on one side and externally rotates the humerus.

Exercise for the supraspinatus muscle

The supraspinatus exercise can be performed with either a pulley system, tubing, or weights as they are all equally effective. The person positions the arm at a 45-degree angle from the side of the body and then raises the arm until it is shoulder height. Whether to do the exercise with the thumb up or down for maximum isolation of the supraspinatus is controversial.

Rotator cuff tears – common cause of shoulder pain

The shoulders are a major trouble spot, taking abuse at every turn. We overload them as we work the biceps, triceps, chest, lats, lower back and legs. They have no place to hide. Throw a ball, shoot a basket, tackle a speeding body, take a nose dive over the handlebars and the shoulders are there being pounded, wrenched, rotated and separated.

However, most shoulder injuries are not centered on the large outer deltoid muscles, but the smaller underlying rotator cuff. One of the most common injuries is a rotator cuff tear. Unfortunately once you tear it, surgery may not even restore it properly, and you may be permanently prevented from working your upper body properly.

A rotator cuff rear frequently occurs after seemingly minor trauma to the musculotendinous  unit of the shoulder. However, in most cases the pathologic process responsible for the tear has been a long time in the making and is the result of ongoing tendinitis.

In addition to pain, patients suffering from rotator cuff tear often experience a gradual reduction in functional ability because of decreasing shoulder range of motion that makes simple everyday tasks such as combing one’s hair, fastening a brassiere, or reaching overhead quite difficult. With continued disuse, muscle wasting may occur, and a frozen shoulder may develop.

Related Muscles

Shoulder rotators sit deep, under the deltoid muscle in the shoulder.

Closing Thoughts

The shoulder rotator muscles lie beneath the large deltoid muscles and allow the arms to rotate into various positions. Despite the fact that they are barely visible muscle group, they are essential for shoulder stability and strength. In other words, they hold the shoulders in place. Bodybuilders and powerlifters frequently develop problems in that region from the years of heavy pressing movements. The best way of treating a rotator cuff tear is preventing it in the first place. Do shoulder rotations as a simple exercise involving very light weight. You should perform a few sets of these important exercises before any shoulder or chest exercises.


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