Determining a musculoskeletal system’s pre-stretched state using continuum–mechanical forward modelling and joint range optimization

Abstract

The subject-specific range of motion (RoM) of a musculoskeletal joint system is balanced by pre-tension levels of individual muscles, which affects their contraction capability. Such an inherent pre-tension or pre-stretch of muscles is not measureable with in vivo experiments. Using a 3D continuum mechanical forward simulation approach for motion analysis of the musculoskeletal system of the forearm with 3 flexor and 2 extensor muscles, we developed an optimization process to determine the muscle fibre pre-stretches for an initial arm position, which is given human dataset. We used RoM values of a healthy person to balance the motion in extension and flexion. The performed sensitivity study shows that the fibre pre-stretches of the m. brachialis, m. biceps brachii and m. triceps brachii with $$91\%$$ 91 % dominate the objective flexion ratio, while m. brachiradialis and m. anconeus amount $$7.8\%$$ 7.8 % and $$1.2\%$$ 1.2 % . Within the multi-dimensional space of the surrogate model, 3D sub-spaces of primary variables, namely the dominant muscles and the global objective, flexion ratio, exhibit a path of optimal solutions. Within this optimal path, the muscle fibre pre-stretch of two flexors demonstrate a negative correlation, while, in contrast, the primary extensor, m. triceps brachii correlates positively to each of the flexors. Comparing the global optimum with four other designs along the optimal path, we saw large deviations, e.g., up to 15$$^{\circ }$$ ∘ in motion and up to 40% in muscle force. This underlines the importance of accurate determination of fibre pre-stretch in muscles, especially, their role in pathological muscular disorders and surgical applications such as free muscle or tendon transfer.

A full body musculoskeletal simulation model for dynamic analysis of strength training using MATLAB tools

“…The change in biceps brachii muscle force observed in our study aligns closely with the findings of Avci and Röhrle, who investigated the pre-stretched state of musculoskeletal systems using continuum-mechanical forward modeling and joint range optimization. Their study highlighted significant variations in muscle force during different phases of movement, which is consistent with the muscle force patterns we observed during dynamic exercises such as the dumbbell curl [45]. In another study, Schutz et al analyzed shoulder and elbow joint moments during bench press training using a quasi-static inverse dynamics approach.…”