Infraspinatus

What is an Infraspinatus muscle?

Infraspinatus is a thick muscle, triangular in shape, taking the greater part of infraspinatous fossa. Mainly, infraspinatus muscle is responsible for the lateral rotation of the arm as well as the stabilization of the shoulder joint. Infraspinatus muscle is one of rotator cuff’s four muscles.

Origin and Insertion of Infraspinatus muscle

The infraspinatus mucle medially attaches to infraspinous fossa as well as laterally to the facet in the middle of humerus’ greater tubercle. The muscle is covered by infraspinatus fascia from which it arises and also separates it from teres minor and teres major. Also, it forms tendinous fibers in the ridges located at its surface as while forming fleshy fibers starting at the infraspinous fossa’s medial two thirds.

These fibers join into a tendon that glides above the spine’s lateral or side border. These also traverse the shoulder joint’s capsule in the outer part. The infraspinatus tendons are slotted into the central impression of humerus’ greater tubercle. This infraspinatus tendon insertion is actually larger in comparison to supraspinatus.

How does the Infraspinatus muscle function?

Picture 1 – Infraspinatus
Source – sportsinjuryclinic

As earlier stated, the infraspinatus muscle is responsible for the stabilization of the shoulder joint as well as assisting the arm in its outward rotation. Primarily, it horizontally extends as well as assists in the shoulder joint’s lateral rotation. It forms the shoulder’s key external rotator. In case of a fixed arm, the infraspinatus muscle holds the scapula’s inferior angle with the assistance of the deltoid, subscapularis and teres minor.

Together with the teres minor, they are responsible for glenohumeral joint’s extension as well as the outward rotation of the humerus’ head.

Weakness of the Infraspinatus muscle

There is an enhanced risk of shoulder injury when one is throwing or in traverse adduction and flexion activities of the shoulder. This is especially in cases where the elbow has traveled behind the shoulder. This risk is increased with long-drawn out shoulder girdle. The infraspinatus and the teres minor counteract the Petroralis Major’s strong forces of stabilizing as well as dislocating. The counteracting force is very important during a traverse adduction or flexion initiation as well as the throwing movement’s end.

What are the trigger points of the Infraspinatus muscle?

Many are the times when trigger points are ignored because of the distinctive referral pattern of the infraspinatus. As much as the infraspinatus shoulder is placed on the back, you need to note that the shoulder’s front bears the major referral pain. Pain would also occur along the shoulder’s outer portion while going to upper arms.

In most cases, the infraspinatus experiences frozen shoulder, a condition that results in stiffness and weakness of the shoulder. The scar and adhesions tissue located in the shoulder joint mainly causes this.

Infraspinatus muscle injury

It would be imperative that we first determine how shoulder injuries occur. These are mainly caused by habits rather than any predisposing factors. Repetitive straining or habitual overloading associated with the outward rotation of the arm would cause injury of infraspinatus muscle. This is especially when you keep your arms overhead or in front, for example, working on the computer without support for the elbow or driving a vehicle with hands on the wheel. In addition, repeatedly reaching the back would cause infraspinatus tear for example, controlling the computer mouse etc.

Symptoms of infraspinatus tear

Symptoms of infraspinatus injury include :

• Pain in the front shoulder- Infraspinatus pain goes down into the biceps feeling like it is in the shoulder joint. In addition, the shoulder blade, neck as well as side shoulder may hurt.
• Infraspinatus atrophy-You would have limited mobility making it difficult to reach back or even lie on the shoulder as you sleep.
• Weak or stiff shoulder- the arms and the shoulder would be easily tiring out on a single side as compared to the other. The arm could also get numb, still as well as have the muscles imbalanced.

Can infraspinatus injury be prevented?

Looking into the infraspinatus injury, one would acknowledge that it is possible to prevent its occurrence especially by changing the sitting and exercising habits. In this endeavor, one would be best placed sitting in the correct manner. In this case, you need to sit with the shoulder blades drawn back and down. In addition, you could prevent the stressing of the muscles by taking more water. In addition, you definitely do not have to stress one hand for too long. Get the other hand to work as well in order to give the other one a break. Get a quality chair that incorporates elbow support in order to enhance the relaxation of the shoulders.

How are infraspinatus injuries treated?

Having in mind that the infraspinatus is part of the four muscles of the rotator cuff’s, it therefore means that the other muscles will have to compensate for the injured or weakened infraspinatus muscle. This definitely would not be the best having in mind that the whole shoulder would be in problem. A condition commonly called frozen shoulder would actually result if the shoulder is not treated in time or the injury taken care of earliest possible.

Fortunately, the treatment of the infraspinatus injury does not have to be complex. One only has to change their behavior. To start with, it would be important that you fix the posture especially when you are exercising or sitting. Flaring or hanging shoulder blades make for bad posture. In addition, you can incorporate some exercises for example the realignment of the pelvis, stretching the doorway chest as well as shoulder dislocations. These would improve the mobility of the upper body, pull down the shoulders and strengthen the traps and the upper back.

In addition, you need to go slow with lifting weights. Reduce the weight while taking time to improve the technique and build back slowly.

Another remedy would be carrying out therapy on the trigger points. These are the knots that occur in the muscles when they are over-stimulated. They cause the stiffening or the shortening of the muscles. In this case, the muscle attachments would be stressed by movement and can cause damage to the connective joint as well as distort the joints. Testament to the joint stress resulting from trigger points is popping of the shoulder joints. You need to acknowledge that the incorporation of exercises would aggravate the pain as irritate further the trigger points. However, the trigger points can be removed by massaging the infraspinatus. In this case, the shoulder blade should be massaged by the use of a tennis ball alongside a wall. In addition, you could massage the Rhomboid, which lies between the spine and the shoulder blade. You still could use a ball in this case.

Infraspinatus exercises

It would be important that you acknowledge that the infraspinatus muscle is very weak. This therefore heightens the risk of shoulder injury. This is especially when you are undertaking activities like rowing, throwing etc that would rotate your shoulder or have the elbows brought behind. It would be important that you undertake exercises which would strengthen the muscle as well as save you time and pain.

The following are the infraspinatus exercises that one can follow to minimize the risk of infraspinatus tear.

• Side-lying abduction – this is an exercise that strengthens the infraspinatus alongside the other rotator muscles like subscapularis and supraspinatus. This is an exercise that has been found to be most effective in comparison to the others. In this exercise, you would incorporate the use of a dumbbell which would provide resistance. It is recommended that you use one that weighs between 5 percent and 8 percent of the body weight in case of women and men respectively. This weight is however not limited to those as it will depend on the number of repetitions that you would want to perform. In this exercise, you would have to lie on the left side while holding the dumbbell on the right hand. The palm should be facing you while the hand is on the floor. You would than rotate the right arm to an angle of 45 degrees from the torso while the elbow still touches your body. Rotate the arm to the floor.
• Incline lever row – this exercises the back muscles as well as the infraspinatus and the shoulders. You would have to use a machine to perform the exercise. In this case, you would lie on incline platform with your face down. Your chest should go to the bench with the feet pressing against footrests. The knees are in this case slightly bent. You then reach down to the handles and grab them with overhand grip. In this case, your palms will be facing your feet. You would then proceed to pull the gripped handles to the sides in which case your elbows will be behind you. While you row, ensure that the neck is straight and not extended forward. In addition, ensure that you do not get off the incline platform. You would then proceed to lower the machines’ handles before straightening the arms back into starting position.

The  infraspinatus exercises are very effective in strengthening the infraspinatus muscles. It would be important that you undertake the infraspinatus exercises on regular basis while also taking care not to use too much weight as to damage other muscles.

Reference:

http://radiology.rsna.org/content/226/1/161.full.pdf

http://www.exrx.net/Muscles/Infraspinatus.html

http://www.myweightlifting.com/infraspinatus-muscle.html