One of the most important features of endurance training was to increase the weight of the dumbbells between sets. According to the relationship of the contractile force in the muscles, the porpuse was to increase muscle growth by gaining more contractile force. Previous studies had generally examined muscle behavior under maximum force. However, the relationship between increased dumbbell weight and muscle contraction was not fully investigated. The aim of this study was to investigate the mechanical behaviors resulting from the application of dynamic forces that occur during the dumbbell curl exercise on muscle fibers. In this study, biceps brachii muscle force during biceps curl exercise performed with two different weights (5kg and 10kg) was calculated. Then, a finite element model was developed and mechanical behaviors in the biceps muscle fiber during exercise were investigated. It was achieved that there was no linear correlation between dumbbell weight and muscle force. It was observed that when dumbbell weights were doubled (100%), the maximum muscle force and deformation increased by 83.13% and 84.92%, respectively. The results showed that increasing excessive weight during exercises will not be as beneficial for muscle development as expected.

Muscle contraction is a complex phenomenon that begins with chemical processes, continues physiologically, and leads to the production of force. Although the production of force in the muscles depends on factors such as temperature, age, gender, race, but the most important factor is the external load applied to the muscle. Determining the effects of increased load on muscle mechanics is of particular importance for planning exercise activities and rehabilitation processes. In this study, the effects of different external forces on the stress and pressure behavior of the muscle were examined on a simplified model of the biceps. Accordingly, a finite element model of the biceps brachii muscle fiber was constructed. The application of different static loads (2.5 -100 N) on both the proximal tendon (one-directional) and the proximal and distal tendon (bidirectional) together were investigated. According to the results, it was found that the external force applied in both directions causes a significant increase in displacement behavior and stress.