||The bench press has become the most widely recognized and frequently performed exercise in weightlifting routines today (Thompson, 1994). Though there are many different variations of the bench press, the primary goal remains the activation of the pectoralis muscles (McCullough, 1997). The pectoralis major has been found to be one of the primary contributing skeletal muscles in the bench press, affected by numerous factors (Barnett, Kippers and Turner 1995). These include; gender, previous experience, hand position as it relates to grip width on the bar, pace of the movement, the barís path, total range of motion, the amount of weight in relation to strength capabilities, the angle of the bench, amount of back extension, and shoulder position, determining whether adduction in the sagital plane or abduction in the horizontal plane is being performed. All of those factors can conceivably play a role in the level of activation of the pectoralis major muscle, which as previously mentioned, is the primary motivation in bench pressing.|
The pectoralis major is comprised of two heads, each able to be activated independent of the other to a small degree. The sternocostal head of the pectoralis major was found to be activated more in a horizontal bench press than in either incline or decline (Barnett, et. al., 1995). In addition, the clavicular head of the pectoralis major during the horizontal bench press motion produced similar electromyography (EMG) signals to that of the incline bench, and greater signals than that of a decline bench (Barnett, et. al., 1995). With this, an argument could be made that bench pressing with the standard horizontal bench should produce equal or greater EMG readings on both heads of the chest than either incline or decline bench press.
As mentioned earlier, however, EMG readings with the bench press are dependent on many factors. Grip width has been found to be a factor, helping to determine the level of activation of the pectoralis major and the triceps brachii. McLaughlin (1985) has found that adopting a wider grip width has shown to produce a greater extent of pectoral involvement. This, however, was only tested at sub maximal weight. Various fluctuations in the percent max of weight used has been shown to have an impact on the bar path, which could conceivably impact pectoral involvement. Most research has been conducted using a percent of predetermined maximal capacity, varying between 20% and 81%. The bar path through this range has been shown to differ from those utilized in tests where maximal weight is used (Wilson, Elliott, Kerr, 1989).
Another factor that could produce change in the EMG readings is the pace of repetitions. In many studies, the bench press is monitored by a metronome and has most often shown up with a 1 second eccentric phase and 1 second concentric phase (Barnett, et. al., 1995).
The range of motion being used and particular points inside of that range of motion may also affect EMG readings. The range of motion that has produced the greatest activation of the pectoralis major in previous studies (Elliot, Wilson, Kerr, 1989), is the start of the concentric phase. This would seem to indicate the change in momentum from eccentric to concentric, just following the greatest moment of tension produced.
Furthermore, the range of motion for particular joints also helps to determine which muscle groups are being more dominantly recruited. Often in other studies the shoulder angle is measured using a goniometer to distinguish between adduction and flexion.
Through all of these variations, men and women, who generally have different techniques for bench pressing through different form, grip widths, and range of motion, do not actually appear to have any significant discrepancies in muscle recruitment or the timing of events (Abendroth-Smith, Griswold, 1998).
Once everything of form is understood for the consistency of the motion, the equipment available may also play a role. The manufacturers of most exercise machines are forced to compromise the mechanics of the equipment to allow its development to appeal to the "average fit" and therefore have more market appeal (Hughes, 1997). Though there is very little research available on the cable crossovers and its impact on the pectoralis major, it was still selected as the comparative movement on merit of its free range of motion that is not limited in this way to a particular body structure. Because of this, body frame is not a factor that will affect the outcome of the results.