Is there any reason to train bench press using a reverse grip? I was working yesterday and noticed two guys doing bench press with reverse grip. After asking them the reason behind this, they told me they were targeting the most medial aspect of the pecs and were training another angle of the pecs (they were lying on a flat bench). I mentioned that to train "another angle," you would either lie on an incline or decline bench and to train the most medial part of the chest, you would perform chest flies or cable cross overs (for example). They weren't so sure, so I just left it at that and decided to write to you instead. Is there any validity at all in their reasoning? Is there any purpose in doing bench press with a reverse grip? Thanks for your help.
This is a great example of "GYM SCIENCE" (Flex magazine) versus the "TRUE SCIENCES" (Biomechanics, Physiology, etc.) The two gentlemen you spoke with were/are misinformed.
The pec major's fiber alignment is generally horizontal with the minor exception of the slight diagonal angles of the upper and lower fibers. This fiber alignment is what allows the pec major to perform horizontal adduction of the upper arm such as in a bench press. This means there is indeed upper, middle and lower pecs (relatively).
However, from an exercise standpoint, there cannot be an "inner" and "outer" pec because the fibers do not run that way. Muscle fiber alignment as it relates to direction of resistance will ultimately determine what muscles are being trained. There is a myth that when pec flys or close grip bench presses are performed, the elusive "inner pec" is being emphasized. The truth of the matter is, what you've done is simply shorted the pec major to a greater extent then if a standard grip width was taken, which is basic mechanics.
In a "reverse grip" bench, the wrists are supinated, forcing the shoulders to come out of the transverse plane (shoulder horizontal AB/ADduction) and into the sagittal plane (shoulder flexion/extension). The pec major is actually now in a WORSE position to pull due to the fact that it's fibers are in poor fiber alignment to do so. The anterior deltoid is left to do the majority of the work. This is why you'll likely never see an individual "reverse grip bench" as much weight as she/he can regularly - fewer fibers are doing the work!