Muscle force of the shoulder complex with different external loads and movements: a biomechanical simulation analysis

Abstract

The analysis of the force produced by each muscle has great clinical relevance, guiding professionals to training or treatments that are more precise, specific, and individualized to structures and muscles of interest. The aim of this study was to estimate the individual muscle force of the shoulder complex during three shoulder movements with three different loads. Fifteen healthy male subjects with right upper limb dominance performed five repetitions of shoulder abduction, scapular plane elevation (scaption), flexion movement in 120° with a speed of 45°/s and the with a load defined as 5% of the subject weigth. The movements were evaluated in three situations: without external load, with dumbbell, and with elastic resistance. Dvideow software was used to analyze the kinematic data, and OpenSim software was used to estimate individual muscle force with an upper limb biomechanical model. Deltoid (anterior, middle and posterior), supraspinatus, infraspinatus, teres (major and minor), subscapularis, and long biceps brachii were estimated. For statistical analysis, a generalized estimating equation model was used with SPSS 20.0. Almost all muscles presented statistical differences (p<0.05) with varying loads in all tested movements. It can be concluded that despite the lack of validation for the present biomechanical model, we could see different individual muscle forces through different external loads identifying which exercise produce more force in certain muscles guiding a more specific rehabilitation/exercise program.