## 4 Discussion
In this sense, the bench angle interferes with the activation between the pectoral muscle portions and increases the participation of other muscles such as the deltoids when there is an inclination of 45 degrees. This must be considered for the prescription of exercises according to the planned objective. These variations between authors [31; 35; 49; 50; 53; 57; 66; 69] may be due to modifications in the placement of the electrodes by the classification or division of the major pectoral according to different criteria. Since an electrode placement in the horizontal fibers of the sternal portion did not show significant changes between the different angles of the bench, while a significantly lower activation was observed in the inclined press if the electrode placement was carried out in the low or descending fibers of the sternal portion [35]. In training sessions, it is common to modify the traditional bench press (BP) in various ways, such as increasing instability, with the expectation of achieving different results. However, it is important to note that the outcomes of such modifications may not always align with the intended objectives. In this study, variations that introduced instability were performed with the same relative load and executed in the same plane and trajectory to prevent any changes in the results [51; 56; 68]. No differences were obtained in any of the subgroups and phases of contraction (concentric-eccentric) analyzed, in the execution of the press bench with different materials that could increase the instability. These changes to an unstable surface can be effective as long as the objective of execution is to obtain a greater involvement of the stabilizing muscles, due to a greater activation of these muscle groups in exercises with greater instability [51; 59; 68; 77]. In addition, one should not forget the increased risk of accidents in unstable environments, especially in inexperienced athletes, who may not be knowledgeable about the changes in lifting load due to increased instability in execution, having no effect on increased force production [68; 78; 79; 80; 81]. Furthermore, not only is the modification of a BP usually used as an exercise to stimulate the pectoralis major muscles in a different way, also different pushing exercises are selected for very different purposes, most of them trying to implicate the pectoralis major in a similar way to the traditional BP and even increase its involvement [69]. In the results of the analysis in relation to the comparison with the push up variant [30; 69], it showed a greater effect on the activation of the pectoral in the traditional BP. However,the difference in the relative load between the subgroups should be considered, because the activation was greater when pushups were performed suspended or with an elastic resistance in comparison with BP at 50% RM, changing direction from 70% RM [30]. In regard with other variants no push up, traditional BP activated pectoralis major significantly more than the variants [30; 55; 58; 60; 61]. However, if we focus on a specific subgroup whose variant is BP performed with dumbbells, these differences are not shown and the activation is similar [58; 61]. In fact, the execution with dumbbells could have a greater range of movement, but as can be seen in the study by [PERSON] et al. [61], and also in the study by [PERSON] et al. [82], the % of activation of the pectoralis major during the complete contraction is greater in the traditional BP executed with a bar. The pectoralis major can be worked to a greater extent by achieving a higher rate of activation during the BP movement. This study highlights the need to monitor the activation range throughout the entire movement, rather than just relying on the absolute or normalized electrical activation value. Additionally, variations in pushing exercises that yield similar levels of pectoralis major activation but involve different movements can lead to significant neuromuscular adaptations [83].