Rotational action of the supraspinatus muscle on the shoulder joint

Muscle loading and activation of the shoulder joint during humeral external rotation by pulley and variable resistance

“…Our data showed that the activity of supraspinatus increased markedly after 60°, which did not occur on the VR machine, and consequently it was more activated in CP exercise. On the VR machine, the support pad for the elbow fixed the abduction angle to the desired position, thus, it is fair to assume that there was a lower need for stabilization/abduction activity from the supraspinatus muscle when using high loads (Ihashi et al, 1998). In addition, our results agree with those of Fleisig et al (1998) that showed the use of a support, in this case a rolled towel, allowed greater infraspinatus activity compared with no support.…”

The Effect of Abduction and Rotation on Footprint Contact for Single-Row, Double-Row, and Modified Double-Row Rotator Cuff Repair Techniques

“…The specimens were clamped with the humerus in neutral rotation, so that the approximate supraspinatus centroid was slightly posterior to the center of the humeral head. 31 Neutral rotation was defined as the point at which loading of the humerus initiated external rotation 16 ; during preloading, the humerus was manually rotated until external rotation was initiated, then secured into the testing apparatus. Because the supraspinatus has been shown to lie just posterior to the humeral head center of rotation, it has been shown to initiate external rotation when starting in neutral rotation.…”

“…Because the supraspinatus has been shown to lie just posterior to the humeral head center of rotation, it has been shown to initiate external rotation when starting in neutral rotation. 16 The testing apparatus has calibrated stop-pegs that control the amount of rotation arc that can be produced. Abduction angle was defined relative to lines along the length of the humerus and the supraspinatus muscle and tendon, as previously described.…”

The Biomechanical Effects of Dynamic External Rotation on Rotator Cuff Repair Compared to Testing with the Humerus Fixed

“…The specimens were clamped with the humerus in neutral rotation. Neutral rotation was defined as the point at which loading of the humerus initiated external rotation 16 ; during preloading, the humerus was manually rotated until external rotation was initiated and then was secured into the humeral testing apparatus. Because the supraspinatus tendon has been shown to lie just posterior to the humeral head center of rotation, it has been shown to initiate external rotation when starting in neutral rotation.…”