Final answer:
The supraspinatus muscle, part of the rotator cuff, is responsible for shoulder abduction. A full-thickness tear impairs this action and results in pain and weakness during arm lifting. Rotator cuff muscles adjust their contraction to stabilize the glenohumeral joint.
Step-by-step explanation:
The action of the supraspinatus muscle is primarily shoulder abduction, which is the movement of the arm away from the body. As one of the four muscles that comprise the rotator cuff, the supraspinatus is integral for stabilizing the shoulder joint and lifting the arm. In the case of a full-thickness tear, such as in a rotator cuff injury, the individual's ability to abduct the shoulder will be compromised, typically leading to weakness and pain during this movement.
While rotator cuff injuries are commonly associated with athletes like baseball pitchers due to the repetitive overhead motion, they can occur in any activity that places excessive stress on the shoulder, such as kayaking. This muscle, along with the other rotator cuff muscles, provides the primary structural support to the glenohumeral joint. The primary role of the rotator cuff muscles is also to serve as "dynamic ligaments" through constant adjustment of their strength of contraction to maintain the positioning of the humerus within the glenoid cavity.