Does enforcing glenohumeral joint stability matter? A new rapid muscle redundancy solver highlights the importance of non-superficial shoulder muscles

• DOI: 10.1101/2023.07.11.548542
• Publication Date: 2023-07-13T04:15:43Z
• Authors: Italo Belli; Sagar Joshi; J. Micah Prendergast; Irene Beck; Cosimo Della Santina; Luka Peternel; Ajay Seth
• Keywords: Solver; Joint stability

Abstract The complexity of the human shoulder girdle enables large mobility upper extremity, but also introduces instability glenohumeral (GH) joint. Shoulder movements are generated by coordinating superficial and deeper stabilizing muscles spanning numerous degrees-of-freedom. How coordinated to stabilize movement GH joint remains widely unknown. Musculoskeletal simulations powerful tools gain insights into actions individual particularly those that difficult measure. In this study, we analyze how enforcement stability in a musculoskeletal model affects estimates muscle activity during movements. To estimate both from recorded movements, developed Rapid Muscle Redundancy (RMR) solver include constraints on reaction forces (JRFs) model. RMR yields activations minimizing weighted sum squared-activations, while matching experimental motion. We implemented three new features: first, computed active passive fiber contributions; second, activation rates enforced be physiological, third, JRFs efficiently formulated as linear functions activations. without was not different control (CMC) algorithm electromyography muscles. efficiency enabled us test 3600 trials sampled within uncertainty differences with enforced. found enforcing significantly increases estimated rotator cuff most Therefore, comparison EMG measurements alone is insufficient validate models.