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The rotator cuff compresses the glenohumeral joint during abduction of the arm, an action known as concavity compression, in order to allow the large deltoid muscle to further elevate the arm. In other words, without the rotator cuff, the humeral head would ride up partially out of the glenoid fossa, lessening the efficiency of the deltoid muscle.
A strain is a type of acute injury that occurs to the muscle or tendon. Similar to sprains, it can vary in severity, from a stretching of the muscle or tendon to a complete tear of the tendon from the muscle. Some of the most common places that strains occur are in the foot, back of the leg (hamstring), or back. [2]
When exercising, exercising the shoulder as a whole and not one or two muscle groups is also found to be imperative. When the shoulder muscle is exercised in all directions, such as external rotation, flexion, and extension, or vertical abduction, it is less likely to develop a tear of the tendon. [55]
The head rests on the top part of the vertebral column, with the skull joining at C1 (the first cervical vertebra known as the atlas). The skeletal section of the head and neck forms the top part of the axial skeleton and is made up of the skull, hyoid bone, auditory ossicles, and cervical spine. The skull can be further subdivided into:
[6]: 123 Inversion occurs at the subtalar joint and transverse tarsal joint. [7] Eversion of the foot occurs at the subtalar joint. The muscles involved in this include fibularis longus and fibularis brevis, which are innervated by the superficial fibular nerve. Some sources also state that the fibularis tertius everts. [6]: 108
When the shoulder is fixed, levator scapulae rotates to the same side and flexes the cervical spine laterally. When both shoulders are fixed, a simultaneous co-contraction of both levator scapulae muscles in equal amounts would not produce lateral flexion or rotation, and may produce straight flexion or extension of the cervical spine.
The shoulder joint, also known as the glenohumeral joint, is the major joint of the shoulder, but can more broadly include the acromioclavicular joint. In human anatomy, the shoulder joint comprises the part of the body where the humerus attaches to the scapula, and the head sits in the glenoid cavity. [1]
Skeletal muscle is arranged in discrete muscles, an example of which is the biceps brachii. The tough, fibrous epimysium of skeletal muscle is both connected to and continuous with the tendons . In turn, the tendons connect to the periosteum layer surrounding the bones, permitting the transfer of force from the muscles to the skeleton.