## 1 Introduction  
Strength training and the use of multi-joint exercises such as bench press has multiple benefits, such as improvements in skeletal muscle health, bone mineral density, production of greater strength, power, and cardiovascular, metabolic [1; 2; 3; 4; 5; 6; 7; 8], and mental health [9; 10; 11; 12; 13; 14; 15; 16; 17]. There are many variables that make up a strength training program, including the choice of exercises, and these depend on the objectives to be reached, as the training results in different physiological and biomechanical stimuli [18; 19]. Whether for health or performance oriented purposes, and among the many types of exercises that can be performed within a strength training program, the press bench exercise is one of the most common and traditional [20; 21; 22; 23].  
The popularity of the bench press (BP) is justified by being one of the most effective exercises to improve strength and power in the upper body [24], in addition to the potential of this exercise for control in training, evaluation, and research [25; 26]. The traditional BP can be executed with a free bar or with a Smith machine [27], because there are strong relationships between movement speed and 1 RM regardless of whether the exercise is performed on a Smith machine or with a free weight bar [28; 29].  
The main muscles involved in the movement are the pectoralis major, the anterior deltoid and the triceps brachial. Each has an integral function in the bar impulsion, and any modification in this exercise affects the development and involvement of the main musculature. Variations in the BP include bar modifications, bench inclination, grip widths, and intensity [27]. To this can be added different push exercises such as push-ups, bench press with dumbbells, exercises with pulleys, as well as different elements to optimize the result [30], being all the other variants of pectoral exercises (OP) interesting.  
In the traditional BP, the width of grip is usually that which allows it to generate a greater biomechanical force in accordance with its anthropometry in order to maintain safety and avoid the risk of injury. In this way, one of the established ways to determine the traditional width is to obtain in a supine position an arm and elbow abduction at 90\({}^{\circ}\) while holding the bar, resulting in a grip width within a range between 150% and 200% of the biacromial distance (BAD) [31; 32].  
Thus, it is of interest to identify the most efficient exercises to achieve high levels of activation to stimulate muscle hypertrophy and increase muscle strength [30; 33]. Electromyography activity (EMG) can measure neuromuscular activation, which is related to the efficiency of an exercise [34]. Maximal voluntary isometric contraction (MVC) was performed to identify the maximum electromyographic reference values used to normalize EMG for each exercise. In addition, interpretation of the EMG signal can be used to assist in the prescription of strength training [35]. It is generally assumed that exercises that produce greater EMG signal amplitudes have greater effects on muscle strength [36].  
Given the diversity of the literature and the lack of a meta-analysis of this topic, the objective of this systematic review with meta-analysis was to compare the EMG activity of pectoralis major of the BP against OP.