China
Africa
Explore chapters and articles related to this topic
Shoulder problems
Published in Richard Graveling, Ergonomics and Musculoskeletal Disorders (MSDs) in the Workplace, 2018
The infraspinatus muscle runs from the infraspinous fossa of the scapula, passes behind the shoulder joint and, like the supraspinatus, attaches to the greater tubercle of the humerus (a ridge or bump on the outer part of the humerus) and to part of the shoulder joint capsule. This alignment means that, when contracted, it rotates the humerus outwards (or helps pull the arm back, depending on the actions of other muscles), unless other muscles are holding the arm in place, in which case it pulls on the scapula. As with the supraspinatus, it also assists in stabilising the shoulder joint.
Muscle recruitment patterns of the subscapularis, serratus anterior and other shoulder girdle muscles during isokinetic internal and external rotations
Published in Journal of Sports Sciences, 2018
Sylvain Gaudet, Jonathan Tremblay, Mickael Begon
Despite the general consensus that rotator cuff muscles are mainly stabilizers of the glenohumeral joint (Sangwan, Green, & Taylor, 2015), our findings suggest that the supraspinatus and infraspinatus muscles behave more as prime movers than stabilizers. Indeed, those two muscles were highly active during external rotations but showed low activity during internal rotations of the shoulder, which concords with findings of previous studies (Boettcher et al., 2010; Decker, Tokish, Ellis, Torry, & Hawkins, 2003). Shoulder stability may also be ensured by surface muscles in certain situations as shown by Blache, Dal Maso, Desmoulins, Plamondon, and Begon (2015) who observed a high co-contraction of the anterior, middle and posterior deltoids, latissimus dorsi and pectoralis major during manual handling, suggesting an attempt to increase glenohumeral joint stiffness. Still, our results showed direction-specific activity levels for the pectoralis, middle and posterior deltoids and upper, middle and lower trapezius muscles. Some of those muscles may still have a stabilizing role (e.g. middle and lower trapezius stabilizing the scapula during external rotations (Boettcher et al., 2010)), yet they also likely contribute directly to the generation of moment force; pectoralis major and latissimus dorsi in IR/IX; middle and posterior deltoids, supraspinatus and infraspinatus in ER/EX.