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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.
Introduction
Published in James P. Kohn, The Ergonomic Casebook, 2020
James Kohn, Celeste Winterberger
The nervous and musculoskeletal systems are also under substantial stress during material handling activities. During bricklaying trunk-twist flexions may result in pinched nerves in the L5/S1 area of the spinal column. Overexertion muscle injuries such as strains of the arm (triceps and brachioradialis), shoulder (deltoids and trapezius), and back muscles (latissimus dorsi, infraspinatus, teres minor and major) may occur.
Musculoskeletal system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
Ultrasound is especially useful in the shoulder for the high incidence of rotator cuff disorders. The four rotator cuff muscles are the subscapularis muscle at the anterior aspect of the shoulder, the supraspinatus at its superior aspect and the infraspinatus and teres minor, which are situated at the posterior aspect.
Variability of Time- and Frequency-Domain Surface Electromyographic Measures in Non-Fatigued Shoulder Muscles
Published in IISE Transactions on Occupational Ergonomics and Human Factors, 2022
Hamad Nasser Alasim, Ashish D. Nimbarte
The major shoulder muscles can be categorized as rotator cuff and non-rotator cuff muscles. Supraspinatus and infraspinatus are the rotator cuff muscles. These two muscles contribute significantly to the stabilization of the glenohumeral joint, and the infraspinatus plays a significant role in the scapular (mid-abduction) plane abduction (Wuelker et al., 1998). The deltoid, biceps, and triceps are the non-rotator cuff muscles. Itoi et al. (1993) reported that the biceps also plays a significant role in stabilizing the glenohumeral joint as an anterior stabilizer when the shoulder is in an abducted and externally rotated posture. Deltoid function was described by previous studies as the primary movers for shoulder joint abduction in scapular (mid-abduction) plane (Alpert et al., 2000). Escamilla et al. (2009) reported that the deltoid was more effective as a shoulder joint abductor at high abduction angles (60°–90°). The biceps and triceps function as the elbow flexors/extensor muscles (Gatti et al., 2008; Lee et al., 2015). In summary, the shoulder muscles investigated in this study have diverse functions and actions, which are required to support the flexibility and the large range of motion of the shoulder joint. Despite such differences in the functionality of the shoulder muscles, the variabilities in their sEMG measures were not very different. The highest variabilities for supraspinatus and infraspinatus were 12.0 and 10.7%, respectively. Middle deltoid, anterior deltoid, and posterior deltoid exhibited the highest variabilities of 11.0, 11.0, and 10.7%, respectively. The highest variabilities for biceps and triceps were 12.2 and 11.4%, respectively.
Comparison of throwing kinematics and muscle activation of female elite handball players with and without pain – the effect of repeated maximal throws
Published in Sports Biomechanics, 2023
Tina Piil Torabi, Birgit Juul-Kristensen, Mogens Dam, Mette K Zebis, Roland van den Tillaar, Jesper Bencke
Furthermore, the infraspinatus contributes to the external rotation of the shoulder, and in collaboration with the other rotator cuff muscles, the infraspinatus serves to compress and stabilise the glenohumeral joint at the instant of maximal external rotation. Optimal positioning of the humeral head at time of maximal external rotation is important, as the risk of impingement is increased in this position (Mihata et al., 2015; Wu et al., 2005). A lower activation of the infraspinatus at this time of the throwing movement may be a potential risk factor, and the data has shown that fatigue significantly reduced the activity of the infraspinatus in the pain group after maximal shoulder extension (DiGiovine et al., 1992; Kelly et al., 2002).