The subscapularis muscle is the largest of the four rotator cuff muscles. It is responsible for internal rotation and adduction of the your arm at the shoulder. Most importantly, in conjunction with the other rotator cuff muscles, it is responsible for dynamic stabilization of the shoulder joint. The shoulder has less connective tissue structure than other major joints. The rotator cuff muscles act as a sort of dynamic muscle/ligament hybrid to stabilize the shoulder joint as you move. Of the important function of subscapularis is to provide dynamic restraint to the back side of the shoulder joint.
Trigger points in your subscapularis cause pain in the back of the shoulder, and sometimes extending down the back of your arm. Referred pain can also develop on the back side of your hand, wrist, forearm.
Subscapularis trigger points are often involved with Frozen Shoulder Syndrome. They are frequently the foundation of an entire range of shoulder dysfunction.



















Structure
Coming from the direction of the spine, subscapularis arises from the inner two-thirds and from the lower two-thirds of the groove on the inside of your shoulder blade. Some fibers develop from tendinous layers, which intersect the muscle and are attached to ridges on the bone; others from fibrous sheaths that separate the muscle from the teres major and the long head of the triceps brachii. This firmly anchors the subscapularis to the shoulder blade and the surrounding tissue. The upper fibers mostly run horizontally and merge with the more vertical lower fibers. They coalesce into a tendon that is inserted into the lesser tubercle of the humerus and the anterior part of the shoulder-joint capsule. The thick lower head of the joint capsule provides a majority of the support for the subscapularis tendon. Tendinous fibers also extend to the greater tubercle with insertions into the bicipital groove as detailed below.Relations

- The upper portion blends with the ‘biceps pulley system’ inserting into the greater tuberosity.
- The thick, flat middle portion inserts into the lesser tuberosity.
- The muscular lower attachment inserts directly into the humerus.



Isotonic Contractions
Isotonic contractions maintain constant tension in the muscle as the muscle changes length. This can occur only when a muscle’s maximal force of contraction exceeds the total load on the muscle. Isotonic muscle contractions can be either concentric (muscle shortens) or eccentric (muscle lengthens).Concentric Contractions
A concentric contraction is a type of muscle contraction in which the muscle shortens while generating force. This is typical of muscles that contract due to the sliding filament mechanism, and it occurs throughout the muscle. Such contractions also alter the angle of the joints to which the muscles are attached.
Eccentric Contractions
An eccentric contraction results in the lengthening of a muscle. These contractions decelerate muscles and joints (acting as “brakes” to concentric contractions) and can alter the position of the load force. During an eccentric contraction, the muscle lengthens while under tension due to an opposing force that is greater than the force generated by the muscle. However, rather than working to pull a joint in the direction of the muscle contraction, the muscle acts to decelerate the joint at the end of a movement or otherwise control the repositioning of a load. This can occur involuntarily (when attempting to move a weight too heavy for the muscle to lift) or voluntarily (when the muscle is “smoothing out” a movement). Strength training involving both eccentric and concentric contractions appears to increase muscular strength and joint stability more than training with concentric contractions alone.Isometric Contractions

