The shoulder joint is the joint in the human body that has the greatest mobility. It is a ball and socket joint and has a degree of freedom of 360° in a healthy state. The low level of bony protection means that it is also the most unstable joint, which requires the greatest muscular protection. Among other things, this function is performed by the rotator cuff – a combination of four muscles whose main task, in addition to internal and external rotation of the upper arm, is to stabilize the head of the humerus in the shoulder joint. The rotator cuff connects the upper arm bone to the shoulder blade and forms a kind of muscular cuff around the joint, hence its name. This prevents the humerus (upper arm bone) from dislocating from the flat joint socket of the shoulder joint or the muscular and passive structures from being injured when high forces occur, such as when throwing movements or hits in martial arts.
The four muscles of the rotator cuff
The rotator cuff is made up of the following four muscles:
Teres minor muscle
The subscapularis (lower shoulder blade muscle) is the only muscle in the rotator cuff located in the front area of the shoulder joint. It has its origin on the front of the shoulder blade, so when viewed from the back, it sits under the shoulder blade and attaches to the front of the humeral head. The subscapularis stabilizes the humeral head during forward movements in the shoulder joint. In its main function it is an internal rotator of the upper arm.
The supraspinatus (upper bone muscle) originates at the upper back of the shoulder blade and runs under the acromion (shoulder roof) through to the humerus. The supraspinatus tendon is most commonly affected in rotator cuff disorders. The reason for this is the very limited space that exists between this tendon, the acromion and the bursa (bursa subacromialis) in between.
So-called "impingement syndrome" is primarily an irritation of the supraspinatus tendon that occurs when it impacts the underside of the acromion during movement of the upper arm. This can be triggered by a muscular imbalance between internal and external rotators, the presence of a bone spur, or an abnormality in the shape of the acromion due to the anatomical bottleneck in this area. Impingement is most severe when the arm is raised laterally beyond 90°, or when the arm is moved up and forward over the head and rotated inward. This position occurs after a throwing motion or at the beginning of the pull-through motion in freestyle swimming. In throwing sports and in swimmers, inflammation of the affected tendon and bursa is relatively common. If the causes are not addressed, supraspinatus tendonitis can lead to a chronic condition.
Shoulder instability can also cause a "secondary" impingement syndrome. This particularly affects swimmers, who often have increased shoulder mobility. A so-called laxity of the shoulder ligaments can mean that the humeral head no longer stays firmly in the socket when the arm is raised. The increased range of motion affects the length-to-tension ratio of the rotator cuff muscles, preventing them from properly stabilizing the humeral head in the glenoid cavity.
The infraspinatus (infraspinatus) arises from the back of the shoulder blade and mostly covers it. The teres minor arises from the lateral edge of the shoulder blade. Both muscles are primarily external rotators of the upper arm. Your tendons run across the back of the shoulder joint and attach to the back of the humerus. The infraspinatus is recruited more into its role as an external rotator the higher the arm is above the head, the teres minor does more external rotation the closer the arm is to the body
Another function of the rotator cuff
The abduction of the arm occurs mainly through the deltoideus (deltoid muscle). As the deltoid abducts the arm from the body, the humeral head is lifted and impacts the acromion. There the is prevented from moving on. The infraspinatus, teres minor, and supraspinatus rotate the humeral head inward and downward at this point, freeing the acromion and allowing 120° abduction of the arm. At this point, the scapula rotates up away from the spine, and the arm can externally move the remaining 60°. Therefore, in order to utilize the full range of motion of the shoulder joint, simultaneous activation of the rotator cuff along with the rest of the shoulder muscles is required.
External Rotators and Posture
Due to our everyday posture, which often requires sitting work in a hand position closer than shoulder-width in front of the body (writing, reading, driving a car, carrying something in front of the body, etc.) or a relatively excessive training of the large internal rotators, such as pectoralis and latissimus, the internal rotators are often tight while the external rotators have too little tension. As a result, in a relaxed position, many people stand with their palms facing back and the backs of their hands facing forward (pronated hand position). Normal and a sign of structural balance of internal and external rotators would be a neutral hand position with the palms facing the body. Targeted stretching of the internal rotators (broomstick stretch) and training of the external rotators can counteract the everyday posture.
Rotator cuff training
Since the muscles of the rotator cuff primarily have a stabilizing function, it makes sense to only train them in isolation at the end of a training session. Pre-fatigue would reduce performance on other upper body exercises such as pull-ups or bench presses.
Below is a 4-phase progression. Depending on the rest of the program, the exercises are integrated as B exercises or C exercises.
Phase 1: External rotation on cable pulley (at hip height), arm on top, horizontal, 3 sets of 8-12 reps, 3011 tempo
Phase 2: External rotation, with dumbbell, seated on Scott bench, elbow on backrest, arm at side next to body, 4 sets of 5-7 reps, 3020 tempo
Phase 3: External rotation, with dumbbell, sitting on side of Scottbank, elbow on rest, arm in front of body, 4 sets of 6-8 reps, 3210 tempo
Phase 4: External rotation, with dumbbell, sitting on flat bench, one leg planted on bench, elbow on knee, with Fat Gripz, 4 sets of 4-8 reps, 4010 pace
External rotation should be trained frequently in order to be able to create a muscular balance with the often dominant internal rotators, which, as mentioned, also include the pectoralis and latissimus muscles. Internal rotation should never be trained in isolation, since an existing imbalance almost always increases or an imbalance can arise.
The execution of the exercises and other advanced variants of external rotation and their periodization are the content of module 2 of the YPSI Trainer B license and the YPSI Advanced Functional Anatomy Seminar.
Good luck with your rotator cuff training!
Image: The rotator cuff muscles from two perspectives - from the front (left) and from the back (right)