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Robert Jan
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Upper and Lower Chest, Can They be Separately Trained?
I'm probably just wasting my time in writing this article, it really is a psuedo-debate and when it comes down to it, who gives a shit? Well, I wrote this article primarily out of frustration, it's just annoying to see "inclines for the upper chest, flat and decline for the lower" everywhere you look. This has to be one of the longest lasting and genuinely senseless myths in bodybuilding, so little old me is writing an article that refutes every single arguement perpetuated (probably to no avail) by those who still believe in muscle shaping. Read and learn...
Killing The Myth
The chest is composed of two different muscles and 5 different heads or parts. First, let's take a look at the pectoral major, which makes up the brunt of the pectorals mass. The pectoral major is split into two heads, the clavicular and the sternocostal (sternal). The clavicular portion of the pectoral major is often referred to as the upper chest, and the sternal as the lower. The clavicular head originates from the anterior clavicle (medial half) and inserts into the humerus (proximal anterior) and the intertubercular groove (outer lip). The function of this muscle is transverse flexion, transverse adduction, internal rotation, adduction, flexion, and abduction of the shoulder. The sternal head of the pectorals major originates from the sternum (anterior), second and sixth ribs, costal cartilages, and inserts into the humerus (proximal anterior) and the intertubercular groove (outer lip). The function of the sternal head of the pectoral major is transverse flexion, transverse adduction, internal rotation, adduction and extension of the shoulder and downward rotation, depression and abduction (initial) of the scapula.
Wait! They DO have different functions! Not really, let's take a closer look. Notice that the only difference here is that the clavicular flexes the shoulder while the sternal does not and the sternal head is used in scapula movement. Let's take a look at what this really means: flexion of the shoulder is bending the joint resulting in a decrease of angle; moving the upper arm upward to the front, in practice this is a front dumbbell raise. This does not come into play in any chest movements; the only time this becomes a factor is during a Dumbbell front raise, which is primarily an anterior deltoid exercise in which the front deltoid would fail before the pectoral major is stimulated, hence making it completely inneffective for stimulating growth in the pectorals major in any way. OK, now let's look at what scapula downward rotation, depression, an initial abduction really are: downward rotation is rotary movement of the scapula; moving inferior angle of scapula medially and downward. In practice, that is basically pulling your shoulders back and downward. Do you do this in chest exercises? No, this is a primary function of the levator scapulae, and not the pectorals that only play a minor role in assisting this movement. Depression of the scapula is inferior movement of the shoulder girdle; moving the scapula down. This is simply pulling the shoulders directly back; again this does not come into play when training the chest although the sternal pectorals are the primary inducers of this. Then we have initial abduction, which is forward movement away the midline of the body; moving the scapula away from the spine during protraction of the shoulder girdle. In practice this is pushing the scapula forward (extend your arms out in front of you and push your shoulders forward without moving your arms). This is primarily a function of the pectorals minor and the serratus anterior; the sternal head of the pectoral major only plays a small role in assisting the movement. Now, let's take a look at the pectorals minor (which is actually considered part of the shoulder in some anatomy text). The pectoral minor has three heads (all three heads have the same function, therefore act as one muscle), and originates from the 3rd and 5th ribs, anterior surface and inserts into the scapula (superior anterior), and the coracoids process (medial border). The functions of the pectoral minor are scapula abduction, downward rotation (during abduction) and depression. Notice that the sternal head also shares the function, but only assists in this movement but the pectoral minor can do complete this movement without the major. As you can see, the sternal and clavicular portions of the pectorals major both share the same functions therefore cannot be separately targeted. You may have also noticed (if you did, good reading) that they appear to have different origins and insertion, but as far as mechanical function of the muscle is concerned, the pectorals major is actually one muscle and functions as one muscle (as explained above). Although the origins and insertion points are slightly different because of the pectorals majors origin from the sternum and the anterior surface of the proximal half of the clavicle this is considered to be an extensive but common insertion and origin for all practical purposes and mechanical function of the muscle. Do you see? Because of the human anatomy it is absolutely impossible to target the upper and lower chest as individual muscles!
The pectoral minor runs underneath of the pectoral major just to the side of the arm pits, to demonstrate this to yourself try this: extend your arms out forward in front of your body as if in the lock-out position of a bench press, now without moving the arm at all just push with your shoulders (protract the scapula) and a small portion of your chest near the arm pit will contract and make your upper and outer chest appear "fuller". Notice how small the effect actually has on your entire chest. Many people mistake a pump or soreness in the pectoral minor as a pump or soreness in the clavicular portion of the pectoral major. Now, the only way to isolate (pretty much, anyway) the pectoral minor is to do the exercise you just performed, by pushing your shoulders without moving the arms, in other words, protracting the scapula. The pectoral minor is involved in all presses, and is also has the function of forward movement away from the midline of the body; moving the scapula away from the spine during protraction of the shoulder girdle. This, in practice, is an incline press movement. Note that this exercise cannot, and will not isolate the pectoral minor in any way, but it will put more stress on it than (say) a decline press, which would give the perception of the upper chest being worked, when in fact it is only the pectoral minor assisting the major and in no way will cause disproportionate hypertrophy in the pectorals as a whole. The reason you may be able to feel one exercise more than another in certain portions of the chest is due to proprioception which is the ability to sense the orientation and relative position of your body in space by interpreting neural feedback related to muscle fiber length and joint position. Proprioception occurs because the nervous system can, in fact, create differentiated neural feedback from motor units depending on the relative length of the component fibers, and this feedback tends to be (or is interpreted by the brain as) more intense when the fibers in question are either shortened (contracted) or lengthened (stretched) in the extreme (Belial, et al, 2001).
To be continued...
The common belief is that the incline press somehow causes the clavicular portion of the pectorals major to shorten more so than the sternal (EMG tests do support this, but not to a great enough degree to promote disproportionate hypertrophy), which is in some cases correct. But, this does not in any way mean that the fibers shortened to a greater degree will hypertrophy and/or produce more force than the fibers shortened to a lesser degree. This is because all of the sarcomeres (longitudinally repeated unit of a myofibril) of one myofibril (longitudinal unit of muscle fiber containing actin and myosin filaments) work in series. The force exerted on any element of a linear series (i.e. by any sarcomere in the myofibril) is equal to the force developed in each of the other elements of the series. Therefore, all sarcomeres of the myofibril exert the same force, and the force registered at the ends of the myofibrils does not depend on its length (Zatsiorsky, 1995, pg. 60). Note about EMG testing - electromyography (EMG) analysis is not considered accurate in measuring muscle fiber stimulation during the eccentric (lowering) portion of exercise, because during eccentric contraction less fibers are stimulated but damaged to a greater degree. Therefore on an EMG test it would read that there is little activity when in fact there is a lot of muscle fiber stimulation (the majority of growth stimulus occurs during the eccentric portion of the lift). The EMG test in itself is also flawed because just knowing which motor units are firing doesn’t mean you can tell which fibers are contracting (which is what EMG tests determine), and the EMG test also does not measure fatigue or take leverage into account. The problem with emphasizing different portions or heads of muscles in in the way they are innervated. Motor neurons are aligned along the center of the muscle; each neuron innervates a number of fibers (through "axons"), the number of fibers varies. When that line of neurons are fired, all of them fire. In other words - when a muscle contracts, it all contracts making sectional hypertrophy impossible. Another often overlooked fact is that even though there may be a different level of activation in fibers, this difference is so small that disproportionate hypertrophy would not result. Additionally the number of test subjects are very small, Tudor Bompa usually uses 3-5 subjects, which leaves a lot of room for error. I could go on and on, but suffice to say that EMG tests are not accurate measures of muscle fiber stimulation and are not capable of predicting hypertrophy. Back to topic - the reality is that a decline and incline press will stress both heads of the pectoral major to a statistically equal degree. So, if one individual did only incline presses or that same individual did only decline presses, then this person would have absolutely no difference in the ratio of clavicular and sternal pectoral hypertrophy. In fact, the individual who performed decline only would have MORE clavicular hypertrophy because the decline press puts the pectoral major in it's strongest position, as well as minimizing the wink links (shoulders and triceps), which means the chest would be more of the primary mover instead of the shoulders (which is another culprit at causing the perception of an upper chest favor ability - pump or soreness of the anterior deltoid which is located on the front of the shoulder) as in an incline press.
If all this is true, then why would someone be sore more so in the upper chest than the lower chest after an all incline versus all decline workout? Well, this goes back to the pectoral minor. First off, soreness is not fully understood as of now; the most commonly accepted theory of muscle soreness is that macrophage activity is the cause (the metabolic activity that is occurring, and the chemicals released by the macrophages (IGF-1, FGF, and certain prostaglandin's) during the process of phagocytosis stimulate the type IV receptors in the muscle, causing pain). So, why would there be more macrophage activity in your upper chest and not your lower? Well, let's take a look back at the chests anatomy. The pectoral major has two heads, the clavicular and the sternal. Then we have the pectoral minor (actually has three heads, but all share the same function so distinction is rarely noted) which runs underneath the pectorals major just about directly to the side of the armpits. The pectoral minor is a separate muscle, with a separate insertion and origin, and a separate function (it initializes a press). If your pectoral minor is sore, your upper/outer chest will be sore. If your pectorals major is sore, you whole chest will be sore. If both are sore, the whole chest will be sore, but more so in the upper/outer portion. This is not making one part of the chest sorer than another is; this is making one muscle sorer than another is. The clavicular and sternal heads of the pectorals major cannot be separated (these are what people refer to as the upper and lower chest), because human anatomy does not allow it.
Certain individuals will be more or less strong in the incline position of a bench press versus the flat or decline positions. Because of this, it would seem to be logical to think that if your incline bench is stronger that your clavicular pectorals is stronger, and if your decline or flat press is stronger it is a product of a stronger sternal pectorals major. However, this difference in strength is actually a factor of the nervous system. When we do an exercise for an extended period (more than 6 weeks, in general) our nervous system becomes optimized in that specific movement by recruiting motor units in a pattern that is optimal for the movement. So, if you concentrate the majority of your efforts on doing the incline press then your nervous system will by optimized in the incline press and not the flat or decline, so your strength will be greater in the incline position. This is in no way a factor of a strength difference between the clavicular and sternal heads of the pectorals major, it is simply a factor of the nervous system being able to perform the incline better than flat or decline because of neurological optimization in the specific plane of movement. There are also other muscles involved in performing a press. The deltoids and triceps are the two major synergists in the bench press, and by altering the angle in which the press is performed you will be able to recruit these muscles more or less. For example, in the incline press because of the more upright position (one of the deltoids primary functions is bending the joint resulting in a decrease of angle; moving the upper arm upward to the front - a military or overhead press) the deltoids will become more involved in the movement which will allow for more weight to be used. This increased activation of the deltoids in the incline press isn’t necessarily a good thing though, because on an incline press the weak links will almost always fail before the chest (this may not be true in certain cases such as pre-fatigue, however). The shoulders and triceps are the weak links, putting the bench on an incline will bring the shoulders more into play, and put the pectorals major in a considerably weaker position. One of the pectoral major’s primary functions is to pull the arms across the chest and downward - therefore a decline press/dips are the best among the presses. A dip/decline press will minimize the weak links (the lats will come into play more, but they act only as a stabilizer and offer little to the performance of a press, and are not a "weak" link and will therefore not fail before the chest), and put the chest in its strongest position consequently increasing the potential for muscle stimulation in the pectorals major (I said potential because you still have to do the work, and if you don’t you won’t reap the benefits, for obvious reasons). I am in no way saying that exercise variation is bad. It does in fact recruit different motor units (in terms of percentage of activated motor units), which will activate different fibers and within reason will ignite additional muscle growth with the nutritional support necessary. This won’t, of course, create sectional hypertrophy in the given muscle, though.
Now, let's take a more real-world approach to answering this controversy. It doesn't take very long to realize that working the upper and lower chest to produce disproportionate amounts of hypertrophy doesn't work in practice, or in theory. Let's go straight to where this phenomenon would be most likely to be seen. The amazing before and after pictures in which normal people like you and I have transformed their bodies to extremes barely imaginable. Note that although steroid use and other illegal practices are often used in these competitions, it would not in any way have an effect on muscle shape, which is what we’re looking for here. Take a look at all of these before and after pictures, have you ever, EVER seen the shape of a muscle (specifically the chest) change shape? If you have, take a look at the pose. For example, the gap between the biceps may appear to be "filled in” if one takes the bicep out of it's fully supinated position. Try it yourself: turn your wrist so that your palm faces up, now turn it back. The brachialis and brachioradialis will "fill in the gap". I’ve heard people refer to Larry Scott to be someone to change the shape of his muscle, in this case his biceps. In early photos of him he would pose with the bicep fully supinated, as he gained experience he learned that keeping the arm semi-supinated filled in the gap to make his bicep appear longer (for the aforementioned reasons).
Enough of what isn’t possible, what CAN you do in regards to muscle shaping? Unfortunately, there isn’t much you can do to change the shape of individual muscles, but what you can do is make these weaknesses less apparent. For example, if your upper chest appears to be underdeveloped then bringing up the pectorals minor and anterior deltoids, as well as increasing the overall size of the pectoral major will lessen the obviousness of this. You can also bring weak body parts up to par with stronger body parts through specialization/prioritization of your training. For example, if your arms are underdeveloped and your legs are overdeveloped then by focusing on your arms by putting more stress on them while simultaneously putting less stress on the legs (by decreasing training volume, intensity, etc) your arms, in time, will become less of a weakness compared to your legs. There is also the much more extreme option of surgery. Through surgery we can alter the origins are insertions of our muscles which would consequently change their shape. This practice has been shown to create very large decreases in muscular strength, coordination, mechanical function, motor unit activation, among other things. This basically means that although the shape of your muscle will be changed it will be at the expense of the proper use of this muscle, which isn’t a very good trade-off for those interested in bodybuilding and/or strength training. When it is all said and done, trying to change the shape of your individual muscles in a complete waste of time because it quite simply just is not possible. Your efforts should be focused on increasing the size of your muscles (muscle hypertrophy), the strength of your muscles, nervous system, and other strength promoting factors and when needed reducing fat mass.
I'm probably just wasting my time in writing this article, it really is a psuedo-debate and when it comes down to it, who gives a shit? Well, I wrote this article primarily out of frustration, it's just annoying to see "inclines for the upper chest, flat and decline for the lower" everywhere you look. This has to be one of the longest lasting and genuinely senseless myths in bodybuilding, so little old me is writing an article that refutes every single arguement perpetuated (probably to no avail) by those who still believe in muscle shaping. Read and learn...
Killing The Myth
The chest is composed of two different muscles and 5 different heads or parts. First, let's take a look at the pectoral major, which makes up the brunt of the pectorals mass. The pectoral major is split into two heads, the clavicular and the sternocostal (sternal). The clavicular portion of the pectoral major is often referred to as the upper chest, and the sternal as the lower. The clavicular head originates from the anterior clavicle (medial half) and inserts into the humerus (proximal anterior) and the intertubercular groove (outer lip). The function of this muscle is transverse flexion, transverse adduction, internal rotation, adduction, flexion, and abduction of the shoulder. The sternal head of the pectorals major originates from the sternum (anterior), second and sixth ribs, costal cartilages, and inserts into the humerus (proximal anterior) and the intertubercular groove (outer lip). The function of the sternal head of the pectoral major is transverse flexion, transverse adduction, internal rotation, adduction and extension of the shoulder and downward rotation, depression and abduction (initial) of the scapula.
Wait! They DO have different functions! Not really, let's take a closer look. Notice that the only difference here is that the clavicular flexes the shoulder while the sternal does not and the sternal head is used in scapula movement. Let's take a look at what this really means: flexion of the shoulder is bending the joint resulting in a decrease of angle; moving the upper arm upward to the front, in practice this is a front dumbbell raise. This does not come into play in any chest movements; the only time this becomes a factor is during a Dumbbell front raise, which is primarily an anterior deltoid exercise in which the front deltoid would fail before the pectoral major is stimulated, hence making it completely inneffective for stimulating growth in the pectorals major in any way. OK, now let's look at what scapula downward rotation, depression, an initial abduction really are: downward rotation is rotary movement of the scapula; moving inferior angle of scapula medially and downward. In practice, that is basically pulling your shoulders back and downward. Do you do this in chest exercises? No, this is a primary function of the levator scapulae, and not the pectorals that only play a minor role in assisting this movement. Depression of the scapula is inferior movement of the shoulder girdle; moving the scapula down. This is simply pulling the shoulders directly back; again this does not come into play when training the chest although the sternal pectorals are the primary inducers of this. Then we have initial abduction, which is forward movement away the midline of the body; moving the scapula away from the spine during protraction of the shoulder girdle. In practice this is pushing the scapula forward (extend your arms out in front of you and push your shoulders forward without moving your arms). This is primarily a function of the pectorals minor and the serratus anterior; the sternal head of the pectoral major only plays a small role in assisting the movement. Now, let's take a look at the pectorals minor (which is actually considered part of the shoulder in some anatomy text). The pectoral minor has three heads (all three heads have the same function, therefore act as one muscle), and originates from the 3rd and 5th ribs, anterior surface and inserts into the scapula (superior anterior), and the coracoids process (medial border). The functions of the pectoral minor are scapula abduction, downward rotation (during abduction) and depression. Notice that the sternal head also shares the function, but only assists in this movement but the pectoral minor can do complete this movement without the major. As you can see, the sternal and clavicular portions of the pectorals major both share the same functions therefore cannot be separately targeted. You may have also noticed (if you did, good reading) that they appear to have different origins and insertion, but as far as mechanical function of the muscle is concerned, the pectorals major is actually one muscle and functions as one muscle (as explained above). Although the origins and insertion points are slightly different because of the pectorals majors origin from the sternum and the anterior surface of the proximal half of the clavicle this is considered to be an extensive but common insertion and origin for all practical purposes and mechanical function of the muscle. Do you see? Because of the human anatomy it is absolutely impossible to target the upper and lower chest as individual muscles!
The pectoral minor runs underneath of the pectoral major just to the side of the arm pits, to demonstrate this to yourself try this: extend your arms out forward in front of your body as if in the lock-out position of a bench press, now without moving the arm at all just push with your shoulders (protract the scapula) and a small portion of your chest near the arm pit will contract and make your upper and outer chest appear "fuller". Notice how small the effect actually has on your entire chest. Many people mistake a pump or soreness in the pectoral minor as a pump or soreness in the clavicular portion of the pectoral major. Now, the only way to isolate (pretty much, anyway) the pectoral minor is to do the exercise you just performed, by pushing your shoulders without moving the arms, in other words, protracting the scapula. The pectoral minor is involved in all presses, and is also has the function of forward movement away from the midline of the body; moving the scapula away from the spine during protraction of the shoulder girdle. This, in practice, is an incline press movement. Note that this exercise cannot, and will not isolate the pectoral minor in any way, but it will put more stress on it than (say) a decline press, which would give the perception of the upper chest being worked, when in fact it is only the pectoral minor assisting the major and in no way will cause disproportionate hypertrophy in the pectorals as a whole. The reason you may be able to feel one exercise more than another in certain portions of the chest is due to proprioception which is the ability to sense the orientation and relative position of your body in space by interpreting neural feedback related to muscle fiber length and joint position. Proprioception occurs because the nervous system can, in fact, create differentiated neural feedback from motor units depending on the relative length of the component fibers, and this feedback tends to be (or is interpreted by the brain as) more intense when the fibers in question are either shortened (contracted) or lengthened (stretched) in the extreme (Belial, et al, 2001).
To be continued...
The common belief is that the incline press somehow causes the clavicular portion of the pectorals major to shorten more so than the sternal (EMG tests do support this, but not to a great enough degree to promote disproportionate hypertrophy), which is in some cases correct. But, this does not in any way mean that the fibers shortened to a greater degree will hypertrophy and/or produce more force than the fibers shortened to a lesser degree. This is because all of the sarcomeres (longitudinally repeated unit of a myofibril) of one myofibril (longitudinal unit of muscle fiber containing actin and myosin filaments) work in series. The force exerted on any element of a linear series (i.e. by any sarcomere in the myofibril) is equal to the force developed in each of the other elements of the series. Therefore, all sarcomeres of the myofibril exert the same force, and the force registered at the ends of the myofibrils does not depend on its length (Zatsiorsky, 1995, pg. 60). Note about EMG testing - electromyography (EMG) analysis is not considered accurate in measuring muscle fiber stimulation during the eccentric (lowering) portion of exercise, because during eccentric contraction less fibers are stimulated but damaged to a greater degree. Therefore on an EMG test it would read that there is little activity when in fact there is a lot of muscle fiber stimulation (the majority of growth stimulus occurs during the eccentric portion of the lift). The EMG test in itself is also flawed because just knowing which motor units are firing doesn’t mean you can tell which fibers are contracting (which is what EMG tests determine), and the EMG test also does not measure fatigue or take leverage into account. The problem with emphasizing different portions or heads of muscles in in the way they are innervated. Motor neurons are aligned along the center of the muscle; each neuron innervates a number of fibers (through "axons"), the number of fibers varies. When that line of neurons are fired, all of them fire. In other words - when a muscle contracts, it all contracts making sectional hypertrophy impossible. Another often overlooked fact is that even though there may be a different level of activation in fibers, this difference is so small that disproportionate hypertrophy would not result. Additionally the number of test subjects are very small, Tudor Bompa usually uses 3-5 subjects, which leaves a lot of room for error. I could go on and on, but suffice to say that EMG tests are not accurate measures of muscle fiber stimulation and are not capable of predicting hypertrophy. Back to topic - the reality is that a decline and incline press will stress both heads of the pectoral major to a statistically equal degree. So, if one individual did only incline presses or that same individual did only decline presses, then this person would have absolutely no difference in the ratio of clavicular and sternal pectoral hypertrophy. In fact, the individual who performed decline only would have MORE clavicular hypertrophy because the decline press puts the pectoral major in it's strongest position, as well as minimizing the wink links (shoulders and triceps), which means the chest would be more of the primary mover instead of the shoulders (which is another culprit at causing the perception of an upper chest favor ability - pump or soreness of the anterior deltoid which is located on the front of the shoulder) as in an incline press.
If all this is true, then why would someone be sore more so in the upper chest than the lower chest after an all incline versus all decline workout? Well, this goes back to the pectoral minor. First off, soreness is not fully understood as of now; the most commonly accepted theory of muscle soreness is that macrophage activity is the cause (the metabolic activity that is occurring, and the chemicals released by the macrophages (IGF-1, FGF, and certain prostaglandin's) during the process of phagocytosis stimulate the type IV receptors in the muscle, causing pain). So, why would there be more macrophage activity in your upper chest and not your lower? Well, let's take a look back at the chests anatomy. The pectoral major has two heads, the clavicular and the sternal. Then we have the pectoral minor (actually has three heads, but all share the same function so distinction is rarely noted) which runs underneath the pectorals major just about directly to the side of the armpits. The pectoral minor is a separate muscle, with a separate insertion and origin, and a separate function (it initializes a press). If your pectoral minor is sore, your upper/outer chest will be sore. If your pectorals major is sore, you whole chest will be sore. If both are sore, the whole chest will be sore, but more so in the upper/outer portion. This is not making one part of the chest sorer than another is; this is making one muscle sorer than another is. The clavicular and sternal heads of the pectorals major cannot be separated (these are what people refer to as the upper and lower chest), because human anatomy does not allow it.
Certain individuals will be more or less strong in the incline position of a bench press versus the flat or decline positions. Because of this, it would seem to be logical to think that if your incline bench is stronger that your clavicular pectorals is stronger, and if your decline or flat press is stronger it is a product of a stronger sternal pectorals major. However, this difference in strength is actually a factor of the nervous system. When we do an exercise for an extended period (more than 6 weeks, in general) our nervous system becomes optimized in that specific movement by recruiting motor units in a pattern that is optimal for the movement. So, if you concentrate the majority of your efforts on doing the incline press then your nervous system will by optimized in the incline press and not the flat or decline, so your strength will be greater in the incline position. This is in no way a factor of a strength difference between the clavicular and sternal heads of the pectorals major, it is simply a factor of the nervous system being able to perform the incline better than flat or decline because of neurological optimization in the specific plane of movement. There are also other muscles involved in performing a press. The deltoids and triceps are the two major synergists in the bench press, and by altering the angle in which the press is performed you will be able to recruit these muscles more or less. For example, in the incline press because of the more upright position (one of the deltoids primary functions is bending the joint resulting in a decrease of angle; moving the upper arm upward to the front - a military or overhead press) the deltoids will become more involved in the movement which will allow for more weight to be used. This increased activation of the deltoids in the incline press isn’t necessarily a good thing though, because on an incline press the weak links will almost always fail before the chest (this may not be true in certain cases such as pre-fatigue, however). The shoulders and triceps are the weak links, putting the bench on an incline will bring the shoulders more into play, and put the pectorals major in a considerably weaker position. One of the pectoral major’s primary functions is to pull the arms across the chest and downward - therefore a decline press/dips are the best among the presses. A dip/decline press will minimize the weak links (the lats will come into play more, but they act only as a stabilizer and offer little to the performance of a press, and are not a "weak" link and will therefore not fail before the chest), and put the chest in its strongest position consequently increasing the potential for muscle stimulation in the pectorals major (I said potential because you still have to do the work, and if you don’t you won’t reap the benefits, for obvious reasons). I am in no way saying that exercise variation is bad. It does in fact recruit different motor units (in terms of percentage of activated motor units), which will activate different fibers and within reason will ignite additional muscle growth with the nutritional support necessary. This won’t, of course, create sectional hypertrophy in the given muscle, though.
Now, let's take a more real-world approach to answering this controversy. It doesn't take very long to realize that working the upper and lower chest to produce disproportionate amounts of hypertrophy doesn't work in practice, or in theory. Let's go straight to where this phenomenon would be most likely to be seen. The amazing before and after pictures in which normal people like you and I have transformed their bodies to extremes barely imaginable. Note that although steroid use and other illegal practices are often used in these competitions, it would not in any way have an effect on muscle shape, which is what we’re looking for here. Take a look at all of these before and after pictures, have you ever, EVER seen the shape of a muscle (specifically the chest) change shape? If you have, take a look at the pose. For example, the gap between the biceps may appear to be "filled in” if one takes the bicep out of it's fully supinated position. Try it yourself: turn your wrist so that your palm faces up, now turn it back. The brachialis and brachioradialis will "fill in the gap". I’ve heard people refer to Larry Scott to be someone to change the shape of his muscle, in this case his biceps. In early photos of him he would pose with the bicep fully supinated, as he gained experience he learned that keeping the arm semi-supinated filled in the gap to make his bicep appear longer (for the aforementioned reasons).
Enough of what isn’t possible, what CAN you do in regards to muscle shaping? Unfortunately, there isn’t much you can do to change the shape of individual muscles, but what you can do is make these weaknesses less apparent. For example, if your upper chest appears to be underdeveloped then bringing up the pectorals minor and anterior deltoids, as well as increasing the overall size of the pectoral major will lessen the obviousness of this. You can also bring weak body parts up to par with stronger body parts through specialization/prioritization of your training. For example, if your arms are underdeveloped and your legs are overdeveloped then by focusing on your arms by putting more stress on them while simultaneously putting less stress on the legs (by decreasing training volume, intensity, etc) your arms, in time, will become less of a weakness compared to your legs. There is also the much more extreme option of surgery. Through surgery we can alter the origins are insertions of our muscles which would consequently change their shape. This practice has been shown to create very large decreases in muscular strength, coordination, mechanical function, motor unit activation, among other things. This basically means that although the shape of your muscle will be changed it will be at the expense of the proper use of this muscle, which isn’t a very good trade-off for those interested in bodybuilding and/or strength training. When it is all said and done, trying to change the shape of your individual muscles in a complete waste of time because it quite simply just is not possible. Your efforts should be focused on increasing the size of your muscles (muscle hypertrophy), the strength of your muscles, nervous system, and other strength promoting factors and when needed reducing fat mass.
