A finite element model of the deltoid muscle and biomechanical analysis of the standing dumbbell fly for shoulder exercises

The shoulder joint participates in different resistance training due to its high mobility. In previous studies, deltoid muscle force was investigated by the electromyography method. However, the effects of increasing exercise weight on deltoid biomechanics have not been adequately studied. In this study, shoulder biomechanics in dumbbell fly movements performed with different dumbbell weights were investigated. Accordingly, the biomechanical model of the upper extremity was prepared and the motion analysis of the dumbbell fly exercise was performed. Then, the exercise was simulated with MATLAB Simscape tools. As a result of the simulation, shoulder joint moment and deltoid muscle force were calculated. Thus, the finite element model was performed to examine the mechanical behavior of the deltoid muscle during exercises. In dumbbell fly exercises performed with different weights, the maximum joint moment was 42.82 Nm, 54.32 Nm and 65.83 Nm, respectively. Additionally, the highest muscle force was calculated as 1378 N, 1750 N, and 2121 N, respectively. When the weight of the dumbbell increased by 33.33%, maximum joint moment increased by 26.85% and 21.18%, and maximum muscle force increased by 26.99% and 21.20%, respectively. However, although the dumbbell weight increased by 25%, the maximum stress in the deltoid muscle increased strikingly by 33.33%. Consequently, it was observed that increasing the weight of the dumbbell did not cause the same increase in shoulder joint moment and deltoid muscle force. Moreover, it was found that increasing the weight of the dumbbell increases the stress in the deltoid muscle to a higher extent.

Automated summary

This study investigated the effects of dumbbell weight on shoulder biomechanics during dumbbell fly movements. Through simulation and finite element modeling, it was found that increasing the weight of the dumbbell increased joint moment and muscle force, but more noticeably increased stress in the deltoid muscle.