## 4 Discussion  
This is the first systematic review with meta-analysis that analyses the activation of the pectoralis major in different variations of the bench press exercise. There are three systematic reviews on BP [20; 67; 68]. These studies categorized the included studies by grips, bench tilt, and exercises with greater instability such as the use of dumbbells, at the same that the present. However, they did not show a clear answer on the EMG activity between one modification or another. Several articles go into detail and try to clarify the difference in activation in the grip width of BP [23; 49; 57; 60; 66], even highlighting the importance of a meta-analysis for a better conclusion [49]. In this case, following the inclusion criteria and the scientific literature, we established as a reference for the meta-analysis a normal grip between 150% and 200% of  
Figure 7: (**A**) Forest plot for muscle activation in bench press vs. push up. (**B**) Forest plot for muscle activation in Bench Press vs. other exercise no push up. BAD, since several authors found no difference between these ranges of BAD [31; 49] and more specifically the sternocostal portion [66]. Furthermore, other authors take a grip with 200% BAD as standard to normalize the activation values and be compared with different grip widths [23]. Thus, grips less than 150% BAD were considered a narrow grip. In regard with sternal portion [23; 57; 60], narrow grip shown significantly lower activation compared to the standardized normal grip. Particularly in line with our results, [PERSON] and [PERSON] [31], found that a 190% BAD grip obtained higher levels of activation in the pectoralis than a narrow grip located between 100% BAD and 130% BAD. Similarly, theeman [23] showed that a narrow grip (distance of one hand width between the two hands) the sternocostal portion was activated significantly less than during a 200% BAD, while with 100% BAD it was also activated less, but not significantly. In contrast, other researchers have not found variation in activation of the sternal portion between different grip widths [66; 69]. However, it should be noted that the data from [PERSON]'s study [69] are presented as a mean of activation across different bench conditions (inclined, horizontal, and declined), and thus the specific activation from narrow grip cannot be isolated, which is why it was not included in the meta-analysis. In regards with clavicular portions [23; 66], the analysis shown that the EMG activity is similar in normal width and narrow grip. This coincides with the results of several studies [23; 69], which observed similar activity of the clavicular pectoris during the different grip widths. It should be noted that not all authors are in line with the results of this analysis. [PERSON] et al. [66], showed increased activation of the clavicular pectorals in the 100% BAD grip, compared to 200% BAD, although the study does not specify in which bench inclination option these results were shown. [PERSON] et al. [49] found differences in the pectoralis major between narrower grips than 200% BAD, although this study did not show specific between the clavicular and sternal pectorals, but the result was the mean of both portions so it may interfere, hence the non-inclusion in the meta-analysis. When examining variations in grip such as switching from a pronation to a supination grip [23], the pooled analysis indicates that the sternal portion of the pectoralis is activated similarly in both types of grip. However, it is important to note that this conclusion is based on data from a single article, as there are few studies that have focused specifically on analyzing the differences in activation between different grip types. Conversely, it was found that the clavicular portion of the pectoralis is significantly more active in the supination grip variant compared to the original prone grip variant.