How should we train the pectoralis major?

How can we design a strength training program to maximize the growth of the pectoralis major? What factors do we need to take into consideration, and how do these factors affect the training variables within a program?

What information do we need?

We can use the research literature to enhance our training programs if we search for information about the gross anatomy, regional anatomy, and internal moment arm lengths of a muscle, in addition to its working sarcomere lengths, and susceptibility to muscle damage. Each of these factors provides information that is useful for different reasons (read more).

• Gross anatomy describes the locations of the attachments of the muscle to the skeleton. Learning the basic anatomy of a muscle helps us figure out suitable exercises, and also helps us see how we might alter them to target different muscles within a group.
• Regional anatomy describes the way in which a muscle divides into several internal regions, and this tells us whether we are going to need multiple exercises to train the muscle.
• The internal moment arm lengths of a muscle determine its leverage on the joint, and therefore its contribution to a joint moment, relative to other agonist muscles. This allows us to see where peak force in an exercise joint range of motion needs to be, to target one muscle within a group (or one region of a muscle). We can alter the point where peak force occurs by our exercise selection and by our choice of external resistance type.
• The working sarcomere lengths describe the lengths of the sarcomeres inside a muscle over its joint angle range of motion. It allows us to see if the muscle can experience (1) active insufficiency (and so will be trained poorly by exercises involving peak forces at very short muscle lengths), and (2) stretch-mediated hypertrophy (and so will be trained more effectively by exercises involving peak forces at very long muscle lengths).
• The susceptibility of a muscle to damage is how easily a muscle is damaged by a workout. It is affected by: (1) muscle fiber type proportion, (2) its level of voluntary activation, and (3) the working sarcomere lengths of its muscle fibers. The amount of muscle damage that a muscle experiences after a workout is the main determinant of the frequency (and volume) we can use for training it, and it also influences our choice of exercises (single-joint vs. multi-joint, single-limb vs. multi-limb, and full vs. partial range of motion).

Anatomy

The pectoralis major is a relatively large, fusiform (within each region), and heavily-segmented muscle that originates on (1) the medial half of the clavicle, (2) the lateral side of the sternum, and (3) the anterior sides of the upper six ribs. Its three origins can be used as reference points to subdivide the muscle into clavicular (upper), sternal (middle), and costal (lower) regions. Although they have different origins, each region inserts in a fairly similar place on the upper, lateral side of the humerus.

Owing to the large range of origins down the midline of the body, and the smaller insertion in one place on the upper arm, the two muscles each form a fan shape, one on either side of the torso.

All pectoralis major regions carry out shoulder horizontal flexion (in which the arms are moved in front of the face from the sides of the body, in the transverse plane, as in the pec deck exercise), and shoulder internal rotation, due to the location of its insertion on the lateral side of the humerus.

In contrast, the role of the muscle in other shoulder actions differs between regions. Shoulder flexion is performed by the clavicular (upper) and middle (sternal) regions, while shoulder extension is performed by the lower (costal) region. Shoulder abduction is performed by the clavicular (upper) region, while shoulder adduction is performed by the middle (sternal) and lower (costal) regions.

N.B. Antagonist to the latissimus dorsi

The pectoralis major is commonly considered to be a key antagonist of the latissimus dorsi, which mainly carries out shoulder extension and adduction. Yet, only the clavicular (upper) region of the pectoralis major is an antagonist for all of the primary movements of the latissimus dorsi, because it carries out shoulder flexion and abduction. The lower (costal) region is actually a synergist most of the time, as it carries out shoulder extension and adduction. The middle (sternal) region is sometimes an antagonist and sometimes a synergist, because it performs shoulder flexion and adduction.

In terms of the secondary actions of the latissimus dorsi (shoulder internal rotation and shoulder horizontal extension), the pectoralis major is again not always an antagonist. As a strong shoulder horizontal flexor, the pectoralis major opposes the latissimus dorsi in this secondary movement, but as a shoulder internal rotator itself, it acts as a synergist in this joint action.

The synergistic actions of the pectoralis major and the latissimus dorsi are especially important in throwing. Also, the pectoralis major is a synergist with the latissimus dorsi in scapular plane adduction, which (along with shoulder internal rotation) a key biomechanical feature of the freestyle swimming stroke. Thus, the pectoralis major and latissimus dorsi work synergistically during swimming as well as in throwing.

Practical implications

In practice, the pectoralis major is a relatively large muscle that can be subdivided into three anatomical regions. It performs a wide range of movements for the shoulder. All of its regions can be trained using shoulder horizontal flexion (and technically also shoulder internal rotation). Shoulder flexion and shoulder adduction exercises each also involve two of the three regions. Although it is often regarded as an antagonist to the latissimus dorsi, certain of its three regions actually act as synergists in several joint actions.

Regional anatomy

Anatomically and biomechanically, the pectoralis major can be subdivided into clavicular (upper), sternal (middle), and costal (lower) regions. Even so, the lower two regions (sternal and costal) are often described in research as a single, sternocostal region. Yet, neither subdivision may be strictly accurate, as up to seven subdivisions of the sternocostal region have been identified on the basis of detailed anatomical analysis.

For several reasons, the clavicular region is regarded as being a very distinct region from the rest of the pectoralis major muscle, although it makes up only a fifth (19%) of the total pectoralis major muscle by volume, with the large majority of the muscle (81%) being the sternocostal region. Firstly, the clavicular region is innervated separately from the sternal and costal regions. The clavicular (upper) region is innervated by the lateral pectoral nerve, which comes from the lateral cord of the brachial plexus in most individuals. The medial pectoral nerve innervates the sternal and costal regions, and it comes from the medial cord of the brachial plexus. Secondly, the clavicular region of pectoralis major has usually been found to have a separate distal tendon from the sternocostal region, although they twist around one another such that the clavicular portion inserts more distally on the humerus than the sternocostal region, which inserts more proximally.

Thirdly, an interesting feature of the regional anatomy of the pectoralis major is that the direction of the muscle fibers varies substantially between regions, in whichever way they are analyzed. The fibers of the uppermost regions are directed downwards, the fibers of the middle regions are directed horizontally across towards the shoulder, and the fibers of the lowest regions point almost vertically upwards, a feature that is enhanced by the twisting of the tendons such that the lowest regions insert highest on the upper arm, while the highest regions insert lowest on the upper arm. It is possible that muscle fibers may be most easily activated when they exert force in the same direction as the line of pull of the muscle, and this feature of the muscle fibers within the pectoralis major would contribute to each region displaying a greater role in some joint actions, and a lesser role in others.

Finally, the pectoralis major muscle can be subdivided into regions based on the internal moment arm lengths of each region. Shoulder flexion is performed by the clavicular (upper) and middle (sternal) regions, while shoulder extension is performed by the lower (costal) region. Shoulder abduction is performed by the clavicular (upper) region, while shoulder adduction is performed by the middle (sternal) and lower (costal) regions.

Practical implications

In practice, the pectoralis major can be subdivided into three main regions: a clavicular (upper) region, a middle (sternal) region, and a lower (costal) region, although additional functional compartments seem to exist within the middle (sternal) and lower (costal) regions. Together, the sternal and costal regions make up the large majority of the muscle by volume. Importantly, the regions contribute in different ways to shoulder flexion (or extension) and to shoulder adduction (or abduction).

Internal moment arm lengths

The most well-known role of the pectoralis major is to perform shoulder horizontal flexion (bringing the arms together in front of the face, in the transverse plane). This is a movement that is used in the pec deck exercise and in dumbbell flys. Depending on the technique used, it can also feature in the bench press. However, if the elbows are positioned close to the body with a narrow grip bench press variation, the joint action starts to look more like sagittal plane shoulder flexion, instead of transverse plane horizontal flexion.

In addition to shoulder horizontal flexion, the clavicular (upper) and sternal (middle) regions of the pectoralis major perform shoulder flexion (lifting the arm away from the body in the sagittal plane), while the costal (lower) region causes shoulder extension. Similarly, the costal (lower) and sternal (middle) regions cause shoulder adduction (bringing the arm down towards the side of the body in the frontal plane), while the clavicular (upper) region causes shoulder abduction.

Even so, the extent to which the regions of the pectoralis major are trained in each of these movements is unclear until we assess which other muscles are involved, and which of them have the longest internal moment arm lengths.

#1. Shoulder horizontal flexion

When moving the shoulder at shoulder height in the transverse plane, many muscles are involved. The pectoralis major and anterior deltoid are the main horizontal flexors, and the subscapularis plays a smaller role. The posterior deltoid, infraspinatus, supraspinatus, and teres minor are the main horizontal extensors between the sagittal plane (hands together in front of the body) and the frontal plane (hands outstretched to the sides), although the teres major and latissimus dorsi take over beyond this point (behind the body).

Alongside anterior deltoid, the pectoralis major is a key shoulder horizontal flexor. The shoulder horizontal flexor moment arm lengths of the pectoralis major and of the anterior deltoid both decrease from the frontal plane (hands outstretched to the sides) to the sagittal plane (hands together in front of the body). However, the anterior deltoid has better leverage when approaching the sagittal plane, while the pectoralis major has better leverage before this point. Therefore, exercises that involve peak forces at longer muscle lengths (such as dumbbell chest flys) will likely preferentially target the pectoralis major, while exercises that involve peak forces at shorter muscle lengths (such as machine pec deck using accommodating resistance) will preferentially target the anterior deltoid.

Practical implications

In practice, when using horizontal flexion exercises (such as the pec deck or wide grip bench presses) to train all regions of the pectoralis major, exercise variations that involve peak forces before reaching the point where the hands meet, will better target the pectoralis major.

#2. Shoulder flexion (and extension)

When moving the shoulder in the sagittal plane, many muscles are involved. The anterior and middle deltoids, pectoralis major, and supraspinatus are the primary shoulder flexors, while the posterior deltoid, latissimus dorsi, teres minor, and teres major are the primary shoulder extensors. The role of the pectoralis major varies according to the region, as follows:

• Clavicular (upper) region —the clavicular region has a shoulder flexor moment arm throughout the joint range of motion. Its leverage is small when the arm is by the side of the body, but it increases rapidly to a very high plateau at just 45 degrees of shoulder elevation, declining slightly above 90 degrees.
• Sternal (middle) region — the sternal region of the pectoralis major also has a shoulder flexor moment arm throughout the joint range of motion, although its moment arm length is far smaller than the clavicular region. Its leverage is very small when the arm is by the side of the body, but it increases rapidly to a low plateau at just 30 degrees of shoulder elevation, declining slightly above 60 degrees.
• Costal (lower) region —the costal region of the pectoralis major has a shoulder extensor moment arm only when the arm is above 45 degrees of shoulder elevation. Its leverage increases gradually above this point, reaching a low plateau at 90 degrees of shoulder elevation.

The anterior and middle deltoids (and supraspinatus) are the other main shoulder flexors, and the anterior deltoid has a much longer moment arm than the pectoralis major for shoulder flexion. In contrast to the shoulder flexion moment arms of the pectoralis major, the moment arms of the anterior and middle deltoids increase with increasing shoulder flexion angle. Therefore, shoulder flexion exercises involving peak forces at very low degrees of shoulder flexion (such as very close grip bench presses up to pins) may preferentially target the pectoralis major to some degree, while those that involve peak forces in higher degrees of shoulder flexion will certainly preferentially target the anterior and middle deltoids.

The posterior deltoid, latissimus dorsi, teres major, and teres minor are the other primary shoulder extensors. The shoulder extension moment arms of the teres major and teres minor are unclear, but those of the posterior deltoid and latissimus dorsi seem to decrease markedly with increasing shoulder angle. This indicates that shoulder extension in low degrees of shoulder flexion is unlikely to involve a substantial contribution from the (costal region of the) pectoralis major, while shoulder extension in higher degrees may well involve this region to a meaningful extent. Indeed, studies have found substantial activation of the pectoralis major in the pullover exercise.

Practical implications

In practice, the anterior deltoids are the main shoulder flexors, although the clavicular (upper) and sternal (middle) regions of the pectoralis major do contribute, especially at lower degrees of shoulder flexion. Thus, working with weight in the bottom half of a close grip pressing exercise may target these regions of the pectoralis major, while reducing the involvement of the anterior deltoids.

The posterior deltoid, latissimus dorsi, teres major, and teres minor are the main shoulder extensors, although the costal (lower) region of the pectoralis major does contribute, especially at high degrees of shoulder flexion. Thus, working with weight in the pullover exercise (and perhaps working in a partial range of motion close to the stretched position) may target this region of the pectoralis major, while reducing the involvement of the other muscles.

#3. Shoulder adduction (and abduction)

When moving the shoulder in the frontal plane, many muscles are involved. The anterior and middle deltoids and two of the rotator cuff muscles (the supraspinatus and infraspinatus) are the primary shoulder abductors, while the pectoralis major, latissimus dorsi, teres major, and subscapularis are the primary shoulder adductors. The role of the pectoralis major varies according to the region, as follows:

• Clavicular (upper) region — unlike the other regions, the clavicular region of the pectoralis major has a shoulder *abduction* moment arm that appears once the arm is above 45 degrees of shoulder elevation, and its leverage increases as the arm is elevated further.
• Sternal (middle) region — the sternal region of the pectoralis major has a moderate shoulder adduction moment arm throughout the joint range of motion. It has least leverage at lower and higher shoulder angles, and displays its greatest leverage at 45 degrees of shoulder elevation.
• Costal (lower) region — the costal region of the pectoralis major has a moderate shoulder adduction moment arm throughout the joint range of motion. It has least leverage at lower and higher shoulder angles, and displays its greatest leverage at 60 degrees of shoulder elevation.

While the clavicular (upper) region of the pectoralis major does have a shoulder abduction internal moment arm, it does not seem to contribute meaningfully during shoulder abduction exercises, such as the overhead press (and especially the behind-the-neck overhead press). Thus, shoulder abduction exercises are probably not useful for targeting this region.

The latissimus dorsi, teres major (and subscapularis) are the other primary shoulder adductors, and their shoulder adduction moment arms are generally longer and follow broadly the same pattern, peaking at 70 degrees of shoulder elevation. Above and below this level, their shoulder adduction moment arms are much shorter, but are still present. Therefore, it seems likely that shoulder adduction is first and foremost a latissimus dorsi exercise, while the pectoralis major plays a supporting role.

Practical implications

In practice, the pectoralis major is likely not substantially involved in shoulder abduction or shoulder adduction exercises.

#4. Shoulder scaption

While biomechanical analyses tend to work in distinct planes of movement (transverse, frontal, and sagittal), many movements involve a combination of these joint actions. Shoulder scaption (scapular plane abduction) is a shoulder movement in which the arm is elevated after first being subjected to approximately 30 degrees of shoulder horizontal flexion. The resulting shoulder elevation task is therefore partway between a shoulder abduction task and a shoulder flexion task, although it has more in common with shoulder abduction than with shoulder flexion.

When moving the shoulder in the scapular plane, many muscles are involved. The anterior and middle deltoids, supraspinatus, infraspinatus, and teres minor are the main shoulder scapular abductors. The role of the subscapularis is unclear, but it may also function as a shoulder scapular abductor. The latissimus dorsi, teres major, and pectoralis major are the main shoulder scapular adductors (and seem to contribute to a similar extent), while the posterior deltoid is also a shoulder scapular adductor, albeit only until the arm is raised as far as 90 degrees of shoulder elevation.

As shoulder elevation increases, the moment arm lengths of all of the main shoulder scapular adductors decrease. However, the posterior deltoid ceases to contribute when the arm is elevated above 90 degrees, leaving only the latissimus dorsi, teres major, and pectoralis major. Thus, it may be feasible to enhance the contribution of the pectoralis major during shoulder scapular adduction by adducting the arms in the scapular plane above shoulder height.

Practical implications

In practice, the latissimus dorsi, teres major, and pectoralis major are all shoulder adductors in the scapular plane. This is one of the reasons why the latissimus dorsi and pectoralis major actually work synergistically with each other in some movements, such as the freestyle swimming stroke.

#5. Bench press variations

Although bench press variations are the most commonly-used exercises for training the pectoralis major, it is actually very difficult to identify the role of the pectoralis major and its individual regions in such exercises, because they often involve elevating the shoulder slightly at the same time as horizontally flexing it. Moreover, what shoulder elevation occurs can either take place near to the sagittal plane (when using a close grip) or near to the scapular or even transverse planes (when using a wider grip). Additionally, when the bench press variations involve a different force direction (such as an incline or a decline bench press), complexity is increased further.

Although the internal moment arm lengths of the various regions of the pectoralis major have not been compared between bench press variation movement patterns, some studies have assessed muscle activation of the clavicular (upper) and sternocostal (middle and lower) regions in different bench press variations. These studies have generally found that increasing bench press incline leads to greater activation of the higher regions, while decreasing bench press incline leads to greater activation of lower regions. Similarly, in a study with greater internal validity, isometric horizontal flexion contractions were tested and it was found that the clavicular (upper) region of the pectoralis major was preferentially activated over the sternocostal (middle and lower) regions when force was directed obliquely upwards instead of purely in the transverse plane.

Practical implications

In practice, different bench press variations can be used to target different regions of the pectoralis major. Specifically, incline bench press variations can target the clavicular (upper) region, while flat and decline variations can target the sternocostal (middle and lower) regions. Yet, it is important to note that the large majority (80%) of the muscle is formed of the sternocostal (middle and lower) regions, so most training the pectoralis major should first and foremost involve bench press variations that target those regions.

Working sarcomere lengths

The working sarcomere lengths of the pectoralis major have been investigated in a small number of studies, and vary between regions. The sternal (middle) region spans the longest range of working sarcomere lengths, working through the ascending limb, plateau region, and descending limb of the length-tension relationship. The clavicular (upper) region also works on all three parts of the length-tension relationship, albeit to a slightly lesser extent. In contrast, the costal (lower) region starts on the plateau of the length-tension relationship, and extends onto the descending limb, reaching the same maximum lengths as the sternal (middle) region.

Practical implications

In practice, all regions of the pectoralis major can experience stretch-mediated hypertrophy as a result of strength training using long ranges of motion involving peak forces where the muscle is lengthened. The costal (lower) region region is unlikely to experience active insufficiency when working at short muscle lengths, and the clavicular (upper) region is the least likely to benefit from stretch-mediated muscle growth.

Susceptibility to muscle damage

Research has found that the pectoralis major takes longer to recover from a standardized workout than most other muscles, and it has been reported to take a slightly longer time to recover than the triceps brachii, another muscle that is easily damaged. The ability of any muscle to recover from a workout depends upon its (1) voluntary activation percentage, (2) fiber type, and (3) working sarcomere lengths.

There do not seem to be any studies that have directly measured the voluntary activation potential of the pectoralis major. However, voluntary activation is often quite closely related to the size of a muscle, with larger muscles being less easily activated than smaller muscles. The triceps brachii muscle reaches moderately high (94–96%) levels of voluntary activation, and is slightly larger than the pectoralis major, suggesting that the pectoralis major can probably also be activated to a relatively high extent.

From the little literature that is available, it seems likely that the pectoralis major displays a greater proportion of type II (fast twitch) muscle fibers than type I (slow twitch) muscle fibers. This makes it more susceptible to damage than many other muscles, which are of a more balanced fiber type, because less oxidative type II muscle fibers are more easily damaged than more oxidative type I muscle fibers.

As noted above, the working sarcomere lengths of the pectoralis major reach the descending limb in all regions. This makes the muscle more susceptible to damage than muscles that work only on the ascending limb and/or plateau regions, because greater forces can be exerted by each muscle fiber, which causes them to experience higher levels of mechanical tension.

Practical implications

In practice, the pectoralis major seems to have a “full house” of high levels of voluntary activation, a fast twitch fiber type, and sarcomeres that work on the descending limb of the length-tension relationship, which explains why it takes so long to recover from a workout. Caution is required when training the pectoralis major that frequency is not too high.

What is the takeaway?

The pectoralis major is a relatively large muscle with three regions: the clavicular (upper) region, the sternal (middle) region, and the costal (lower) region. All regions are worked by shoulder horizontal flexion (and also by shoulder internal rotation) but they differ in their contributions to other shoulder movements. This means that the muscle will likely benefit from being trained with several exercises.

Different bench press variations can be used to target different regions of the pectoralis major. Incline bench press variations target the clavicular (upper) region, while flat and decline variations target the sternocostal (middle and lower) regions. Yet, the large majority (80%) of the muscle is formed of the sternocostal (middle and lower) regions. Thus, training should first and foremost involve bench press variations that target those regions.

Although the bench press exercise is the most commonly-used method for training the pectoralis major, single-joint exercises can also be effective. When doing shoulder horizontal flexion exercises (such as the pec deck), variations that involve peak forces with the hands further away from one another (such as dumbbell flys) will be best. It is not known how which region of the muscle is most strongly targeted by shoulder horizontal flexion, but it might be the sternal (middle) region, based on the direction of its muscle fibers. When doing single-joint shoulder extension, the costal (lower) region is the only region to contribute, and provides its greatest contribution at high degrees of shoulder flexion. Therefore, working in a partial range of motion close to the stretched position in the pullover exercise may be most effective for this region.

All regions of the pectoralis major can experience stretch-mediated hypertrophy as a result of strength training using long ranges of motion involving peak forces where the muscle is lengthened. Using full ranges of motion, or working in a partial range of motion close to the stretched position is always likely to be beneficial.

Even so, the pectoralis major has a “full house” of high levels of voluntary activation, a fast twitch fiber type, and sarcomeres that work on the descending limb of the length-tension relationship. Thus, it can take a long to recover from a workout, even if muscle soreness is not obvious. Caution is required when training the pectoralis major that volume and frequency are not too high, and that training methods that cause additional muscle damage are used only sparingly.