Thursday, July 7, 2011

SuppVersity EMG Series - Musculus Pectoralis Major: The Very Best Exercises for a Chiseled Chest

Image 1: The pectoralis major.
(Avandäre:Chrizz @ Wikipedia)
I don't know about you, but about everyone I know (myself included) has, at some point in his/her life, dwelled on thoughts somewhere on the continuum from "Damn, my chest looks flabby!" to "Hell, I got a chest like a chicken". In case you didn't this column probably won't interest you. Otherwise I highly suggest that you read on to learn about the most effective exercises, as measured by electromyography (10 male resistance-trained subjects, mean age 22y, mean body-fat 13%; data from Boeckh-Behrens & Buskies. 2000)...

Exercises with standard equipment
  1. Bench Presses (barbell)
  2. Cable Cross*
  3. Bench Presses (dumbbell)
  4. Butterfly Mashine
  5. Flys (dumbbell)
  6. Pullovers
* the cable cross exercise should be performed actually crossing one's arms low before your body

Figure 1: Degree of muscle activation in comparison to reference exercise barbell pench press; median rank R of exercise among for all participants (data adapted from Boeckh-Behrens & Buskies. 2000)
Notice the interpersonal variety in exercise effectiveness for the Butterfly Machine and the Dumbbell Bench Press. While the mean EMG activation was higher for the Butterfly, the average rank, indicative of how beneficial the exercise is compared to other exercises for each subject on an individual level, is lower. This is a tell tale sign that the perfect match of the ergometry of the Butterfly Machine and the individual physique of the subjects, as well as the exercise form during free weight movements are major determinants of the effectiveness of a given exercise.

Body weight movements  **
  1. Dips
  2. Pushups
  3. Flexing the pectoralis in a fly-like position
** a comparison of weighed and body weight movements using EMG measurements would not be fair, because muscular activation increases with load and the load would be constant and, for advanced trainees, low (relative to their strength) in body weight only exercises
Image 2: Different parts of the pectoralis major
pars clavicularis (1), pars sterocostalis (2),
pars abdominialis (3) (image from DocMartin)

Targeting the individual parts
  • pars clavicularis: descending fibers (upper part)
  • pars sternocostalis: lateral fibers (middle part)
  • pars abdominialis: ascending fibers (lower part)
While there are no "upper" and "lower" chest muscles, its a physiomechanical matter of course that different exercise and working angles will stress ascending, descending and lateral fibers to a different degree. So, while it may be impossible to isolate certain fiber strands, it is well possible to shift the main workload from one strand to the other by selecting appropriate exercises.
Figure 2: EMG activation of different areas of the chest muscle (cf. numbers in image 2) by the bench press exercise at different inclines (data adapted from Boeckh-Behrens & Buskies. 2000)
At first, it may look strange that the inverse(=decline) bench press exhibits the greatest EMG activity not only for the lower chest (as bro-science) would have it, but also for the upper chest. If you do however remind yourself that EMG activity corresponds to the number of motor neurons firing in the area under the electrode, than it is quite obvious that the larger load the subjects were able to handle on the inverse(=decline) bench press resulted in increased motor neuron activation and thus greater EMG values.
Figure 3: Relative activation of different areas of the chest muscle (cf. numbers in image 2) compared to mean activation for each bench press variety (data calculated from Boeckh-Behrens & Buskies. 2000)
I have compensated for this problem by calculating the relative increase in activation compared to the mean activation across the whole chest muscle for each exercise and plotted the data in figure 3. I suspect, this looks much more the way you expected it, doesn't it? Relative to the mean activation pattern over the whole pectoralis muscle, the incline bench press with an angle of +45° provides a 69% more intense stimulation to the "upper chest".

In summary, the inverse(=decline) bench press is the most effective exercise for the pectoralis major as a whole. The incline bench press (+45°), on the other hand, isolates the upper part of the chest muscle, i.e. the descending fibers of the pars clavicularis (cf. image 1) optimally and will thus - as bro-science tells you - bring up your " pecs".


ChestBicepsBackCoreLegsTricepsShoulders
Navigate the SuppVersity EMG Series - Click on the desired body part to see the optimal exercises.

Image 3: Other than bro-science tells you,
EMG measurements show that the main
difference in grip width is not triceps activation,
but a greater involvement of the "upper pecs"
with a closer to shoulder-wide grip
(image from QuakeFitness.com)

An EMG-optimized routine

There is of course a myriad of ways of combining the individual exercises, my personal recommendation for overall chest development (based on EMG measures) would yet be as follows

  1. Decline Bench Press (BB) - for overall chest development + strength (5-10 reps)
  2. Incline Bench Press at +45° (DB) - to emphasize upper chest (8-12 reps)
  3. Cable Cross (making sure to actually cross the cables before your torso) - to get a stretch and peak contractions (12-15 reps)
  4. Bodyweight dips - to wear the muscle out (3 sets to failure)
You may notice that I do not make volume (i.e. set) recommendations. This is due to the fact that I found that everyone has to find what works best for him / her in terms of optimal volume and training frequency. This may also change over time / according to lifestyle factors / nutrition and supplementation.