Estimated Force and Moment of Shoulder External Rotation Muscles: Differences Between Transverse and Sagittal Planes

Abstract

The aim of this study was to compare shoulder muscle force and moment production during external rotation performed in the transverse and sagittal planes. An optimization model was used for estimating shoulder muscle force production of infraspinatus, teres minor, supraspinatus, anterior deltoid, middle deltoid and posterior deltoid muscles. The model uses as input data the external rotation moment, muscle moment arm magnitude, muscle physiologic cross-sectional area and muscle specific tension. The external rotation moment data were gathered from eight subjects in transverse and six subjects in sagittal plane using an isokinetic dynamometer. In the sagittal plane, all studied muscles presented larger estimated force in comparison with the transverse plane. The infraspinatus, teres minor, supraspinatus and posterior deltoid muscles presented larger moment in sagittal when compared with transverse plane. When prescribing shoulder rehabilitation exercises, therapists should bear in mind the described changes in muscle force production.

Differences between clinician- and self-administered shoulder sustained mobilization on scapular and shoulder muscle activity during shoulder abduction: A repeated-measures study on asymptomatic individuals

“…Displacement of the humeral head might change the moment arm of shoulder muscles, impacting on muscle activity levels. With larger moment arm, a muscle would need less muscle force being generated to produce the same moment magnitude 5,33 It is important to understand how sustained mobilisations influence motor synergies of muscles. Our study includes measurements from multiple muscles as a first step in understanding the nature of interactions between muscles.…”