The Science of Training: Pectoralis

By Josh Bryant and Joe Giandonato

Craig Monson with a powerful and aesthetically-pleasing chest

The chest serves as the centerpiece to a powerfully-built and aesthetic physique! 

In bodybuilding, as bigger and bigger mass monsters emerge from peptide-engulfed cesspools sporting arms and legs that dwarf those of the by-gone Golden area, it is interesting to observe that the chest development of this new breed pales into comparison to the old school powerbuilders.

In spite of their volumizing virtues, synthol, nor weekly doses of 5,000 mg of some proprietary ester shelved in a Tijuana pharamcy, will not correct a pec deficit. Natural or not, a properly-designed training protocol will correct it and we are going to share what that entails.

Josh putting Branch Warren through a grueling, holistic chest workout

Anatomy of Pectoralis Major

The pectoralis major (aka the chest), or “the hood” as they call it in Crowbar Hotel, or “pecs” as it is colloquially dubbed by most non-PhD carrying gym bros, is a fan-shaped muscle made up of two heads — the upper head, or clavicular head, and the lower, or sternocostal head.  

The clavicular head makes up only a fifth (19%) of the total pectoralis major muscle by volume, with the large majority of the muscle (81%) comprising the sternocostal head.  The fibers of the uppermost portion of the clavicular head are oriented downwards, contrasted to the fibers of the middle region which run horizontally across toward the shoulder. The lower fibers are directed vertically upward.  Logically, it would make sense that pec fibers are most efficiently activated when they produce force in the same direction as the line of pull in the muscle.

The sternocostal head of your pectoralis major is in charge of  three major motions:

  1. Shoulder extension: Pulling your arm down from an overhead position, for example a dumbbell pullover.
  2. Horizontal adduction: Pulling your arm across your body, like a flying motion.
  3. Internal rotation: Rotation of the shoulder toward the front/midline of your body, this can be a pressing or fly exercise that goes from a neutral or supinated bottom position to finishing in a pronated one.

The clavicular head, or your pectoralis major, is also responsible for three major motions:

  1. Shoulder flexion: Lifting your arm up, like you would to reach overhead; this is why the incline press is so effective for building your upper chest.
  2. Horizontal adduction: Same as above.
  3. Internal rotation: Also same as above.

Fiber Composition

Far too many self-snapping, self-proclaimed aesthetic warriors find their muscle-building salvation from worshipping the almighty pump!  But lo and behold, like most anterior muscles of the body, the pecs are predominantly made up of fast-twitch muscle fibers to the tune of average of 57 to 65 percent fast-twitch muscle fibers.

We can hear the chorus now, “Who the hell cares? Take those test tubes and shove them where the sun don’t shine.”

Educational attainment notwithstanding, you should care if you care about results.

So, in order to maximize hypertrophy of the pecs, you’ll need to hoist some heavy pig iron. Not PR shattering loads, but heavy enough to warrant sets of eight reps or fewer to best stimulate the fast-twitch muscle fibers that earn their paycheck moving weight in that rep range. Additionally, you can incorporate rest intervals of two minutes or more between sets, with cluster sets being a notable exception.  This is why prior to the arrival of growth hormone and insulin, nearly every great bodybuilder was a powerbuilder via variations of heavy bench presses, heavy incline presses, and heavy weighted dips.

Names like Schwarzenegger, Franco, Branch, Coleman, Johnnie Jackson, and Yates all had trained for strength long before gracing the stage and collecting trophies and occupying magazine covers.

In fact, a recent study demonstrated a positive correlation between one-rep max (1RM) in the bench press and the size of the pectoralis major.  

But don’t ignore the pump.  

Forty percent of the pecs are made up of slow-twitch fibers so this means they will also react well to metabolic stress work via high reps, long times under tension, extended sets, short rest intervals, finishers and any kind of pump work.

If we had to choose between heavy weight and pump work to maximize chest hypertrophy, its heavy weight all day BUT we don’t have to and to maximize chest hypertrophy, you must use a holistic approach which includes a spectrum of exercises, weights and rep ranges.

Activating Fibers

When you are executing chest exercises in the gym, all portions of the chest will be activated.  But did you know that certain portions of the chest can be emphasized as bodybuilders have claimed for nearly a century? The literature now concurs.

We briefly discussed how the fibers of pecs are arranged earlier, and that holds serious implications to maximize muscularity.

Upper chest fibers run upward, these fibers will be maximally activated with exercises like incline press variations that involve shoulder flexion where your arms move upward.  

Looking at the middle fibers which run horizontal, activation is most efficiently achieved in exercises where the arms move horizontal (i.e flat bench press variations). 

And finally, the lower chest fibers run downwards, so the best activation is achieved with exercises that involve the arms moving downward like dips.

Mind-Muscle Connection
Josh discussing how to achieve the mind-muscle connection with the chest

In the strength training world, there is a great dichotomy. You have the pink dumbbell crowd that is obsessed with the mind-muscle connection and focuses on it and the exclusion of all else; sure, they can make your chest scream with 10 pound dumbbells for a nice parking lot effect, but try this week in and week out for years—the buck will stop.  Then, of course, the functional crowd that says as long as an exercise has good technique, the mind-muscle connection is irrelevant.

But to lend credence to pink neoprene nation, and to disavow the claims of heavily acronymized pseudo physical therapists, the mind-muscle connection is real.

A famous 2012 study is often cited to prove this.  This study showed that when trained subjects were given verbal cues to focus on chest activation, their chest activation improved by 22 percent contrasted to when no verbal cues were given.  This is HUGE! Just think over the course of months and years.

Debate settled.  

Not so fast!  But an important BUT was left out!  This was with 50 percent of the subject’s 1RM, when the weight increased to 80 percent, verbal instructions showed no further increase in pec activation.
Like most things, the truth is in the middle of the extremes.  

We recommend when performing heavy pressing exercises and compound movements focusing on great technique with the movement, the weight will be so heavy the muscle will get the work.  For example, when doing heavy weighted dips, by leaning forward and getting the proper range of motion with great technique, maximal activation will be achieved.  

For isolation exercises, focus on the muscle; you are not lifting weights from point A to point B, you are intentionally contracting muscles with added resistance.  This mind-muscle connection can further be developed with watching mental movies of yourself, always make sure to initiate the movement you are performing with targeted muscle, accentuating negatives and isometric poses.  This is beyond the scope of this article, but for more detailed information, watch the videos included.

Josh expands further on the mind-muscle connection

Final Thoughts

Like contact sports, 500+ horsepower sports cars, shotgunning beers merely to quench one’s thirst or polishing off a church accordion-sized rack of ribs, muscular chests exude manliness.  Functionally, well-developed pecs will help you bench press more, push your way through crowds of frantic Black Friday shoppers, or as you bulldoze your way to the front of the chow line in county.

Knowledge is power—you now have the power to build powerful pecs.


Beardsley, C. (2019, June 16). How should we train the pectoralis major? Retrieved from
Calatayud, J., Borreani, S., Colado, J. C., Martin, F., Tella, V., & Andersen, L. L. (2015). Bench Press and Push-up at Comparable Levels of Muscle Activity Results in Similar Strength Gains. Journal of Strength and Conditioning Research29(1), 246–253. doi: 10.1519/jsc.0000000000000589

Lehman, G.J. (2005). The influence of grip width and forearm pronation-supination on upper-body myoelectric activity during the flat bench press. Journal of Strength and Conditioning Research, 19 (3), 587-591.
Snyder, B. J., & Fry, W. R. (2012). Effect of Verbal Instruction on Muscle Activity During the Bench Press Exercise. Journal of Strength and Conditioning Research26(9), 2394–2400. 

Srinivasan, R., Lungren, M., Langenderfer, J., & Hughes, R. (2007). Fiber type composition and maximum shortening velocity of muscles crossing the human shoulder. Clinical Anatomy20(2), 144–149. 

Srinivasan, R., Lungren, M., Langenderfer, J., & Hughes, R. (2007). Fiber type composition and maximum shortening velocity of muscles crossing the human shoulder. Clinical Anatomy20(2), 144–149. 

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