Wednesday, August 25, 2010
Bench Press, Part Ten
Developing the Key Muscles Involved in Bench Pressing
3.1 – What We Know About Muscle Involvement in the Bench Press
How do we know what muscles are involved in the bench press, when they’re involved, and how much? Very good question! The prediction of individual muscle force involvement during human sport and exercise motions is no trivial research effort. Three-dimensional musculoskeletal modeling techniques incorporating input from three-dimensional cinematography, electromyography and force transducers on the bar are needed to someday answer this question fully. An example of the complexity of such studies can be seen in reference (1). What’s also important in such analyses is that there are a larger number of unknown muscle forces to solve for than there are equations to work with. Thus, a knowledge of how the body (i.e., the nervous system) calls muscles into play during a bench press is also needed. Needless to say, it’s not a trivial research problem, but along with my colleagues I have been steadily working toward its solution with the “pilot” two and three-dimensional studies discussed in Section 1.4 and throughout this book. Eventually (especially if funding is available) these questions will be answered.
Until then, let’s look at what we know about muscle involvement in the bench press as determined by a number or our pilot studies. Keep in mind throughout the ensuing discussion that these comments must be considered “best” guesses until more sophisticated studies are undertaken. Three pilot studies will be discussed that relate to muscle involvement in bench pressing.
The first study was conducted in 1979 with the kind assistance of W. Kazmaier, World Superheavyweight bench press champion as subject. As depicted in Figure 14, simultaneous film and electromyographic (electromyography, or “EMG”, involves monitoring electrical muscle activity) data was collected as Kazmaier performed a great variety of bench press styles (varying mainly his grip width and where the bar touched his chest). Weights were incremented as he went through each style of bench press for a given poundage. Some of the major conclusions of this analysis were:
(1) The effects of even small (1-2 inch) changes in grip spacing were significant in terms of muscle involvement. Most bench pressers can “feel” this dramatic change in muscle load sharing as they only minimally widen or narrow their grip during bench pressing;
(2) Pectoralis major (sternal portion) was more involved with wider grips and less involved with narrower grips;
(3) Triceps activity was conversely more involved with narrow grips and less involved with wide. Also, at the start of the push off the chest, the greatest burst of triceps activity. The other major area of activity was in the upper portion of the lift, after the chest’s major activity (which was generally from the chest until half to two-thirds of the way up); and
(4) The anterior deltoid was greatly involved in all styles of lift and at virtually all portions of each bench press.
The second study of interest was an investigation of both the bench press and incline presses sponsored by Diversified Products Corporation in 1980 (reference 8, Section 1.4). Similar cinematography with synchronized electromyography of the triceps, anterior deltoid, and both parts of the pectoralis major (sternal and clavicular). The sternal group of fibers are those originating from the sternum (which are most of the fibers in the chest) and the clavicular group originate off the clavicle. Only one subject was used, who was a skilled collegiate powerlifter with five years training history. To summarize the results for the bench press for this subject:
(1) Two grip widths were used, both a wide grip (32 inch) and a narrow grip (18 inch);
(2) When the bar was lowered to the chest all muscles showed considerable activity regardless of grip width. During the lowering, the wide grip involved the triceps less and anterior deltoid more than was the case during the descent with the narrow grip;
(3) As the bar was initially pushed up, peak activity for all muscles was noted shortly after the bar began its upward movement from the chest;
(4) More anterior deltoid activity throughout the entire lift was noted when the wide grip was used;
(5) Triceps activity was less continuous with the wide grip and concentrated most near lockout and barbell support;
(6) When a maximal bench press effort was made the greatest increase in peak activity occurred for the triceps! The smallest increase in peak activity occurred for the anterior deltoid.
As for the second study’s results for incline bench pressers:
(1) Two incline settings were used, and both the wide and narrow grip spacings were again used at each incline;
(2) When going from flat bench presses to the low incline and then to the high incline (no matter what grip was used), pectoralis major (sternal) activity decreased proportionately. This is probably why people who do inclines are often seen arching their backs in an attempt to “flatten” out their chest and get more sternal pectoralis fibers involved. Better to do flat benches!
(3) At either incline the narrow grip involved more activity of the smaller group of clavicular fibers of the pectoralis major than did the wide grip;
(4) Narrow grip inclines provided more triceps activity than the wide grip at either incline;
(5) Peak activity of all muscles occurred at about halfway up at both levels of incline;
(6) At the finish of some repetitions a large burst of anterior deltoid activity was sometimes seen in an attempt to stop the forward drift of the bar between repetitions.
In 1981 a third study was undertaken (reference 6, Section 1.4) using a more sophisticated analysis. Three-dimensional cinematography and musculoskeletal modeling techniques were used to predict involvement of the triceps, pectoralis major (sternal portion only) and anterior deltoid during the three types of bench presses with yours truly as subject (this was discussed more in Section 1.4 and especially 2.8) The results indicated that as far as muscle activity was concerned:
(1) Triceps involvement is so large near the end (or top) of a bench press (especially with a narrow grip), that it is the limiting factor in the lift in this region;
(2) During the rest of the bench press (from just off the chest until perhaps halfway to two-thirds of the way up) the pectoralis major is the limiting factor and most involved;
(3) The anterior deltoid in both grips is near maximally involved during the entire lift, using any style;
(4) A wide grip keeps the pectoralis major at a greater muscle length longer during the lift and permits the muscle to be of more help to successful completion; and
(5) A narrow grip involves the triceps more and the pectoralis major less.
In summary, it should be obvious that the results from these three studies are remarkably consistent even though different research protocols, subjects, etc. were used. I strongly suggest that the information just discussed be studied carefully by the serious bench presser. There is a lot of useful information here with direct implications for training this lift. Even though more advanced studies still need to be done, the results of these three separate studies correlate extremely well and serve as a great starting point for the sections to follow. With these results in mind, let’s now look at how we might train the key muscles involved in bench pressing.
(1) McLaughlin T.M. and Miller, N.R. “Techniques for the evaluation of loads on the forearm prior to impact in tennis strokes”, Journal of Mechanical Design, Vol. 102: 701-710, 1980.
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