The Great "Inner" Chest Debate

[I dont work at Ballys]

If you have something useful to add or discuss, please contribute. I'm using this more for reference to myself so that I can link the information to people that have a question on this.

TO CLARIFY: I chose the chest muscle (pec major) as the reference example because that seems to be the most commonly debated one for some reason or another, there seems to be something "special" about this muscle that lets you work the "inner and outer" portions of it. here is a picture which shows the direction of fibers as they span the muscle:


I am not debating that the upper and lower portions of these fibers can be stressed by performing different chest exercises from different angles, I am stating that the muscle fibers cannot be stressed as they run the length of the muscle from its origin to insertion point. YES, I realize that a single muscle fiber does not run the entire length of a muscle, but it is connected to another muscle fiber and etc.. which runs to the opposite end, and these fibers will contract uniform to eachother IN RATIO which does not mean the EMG numbers will match but that they will in fact be relative to eachother.

COMPARTMENTALIZATION: The division of a single muscle into anatomical compartments each of which has its own primary nerve branch. Therefore, each anatomical compartment can be recruited independently and may function as a separate entity

Before i go into anything too deep, I just want to look at this from a very simple stance. What do people suggest when the question of stressing the "inner" chest is brought up? Cable crossovers right? Or some kind of chest fly. What is the action of the chest? It's a horizontal adductor and internal rotator, so NATURALLY an isolated movement is going to work that muscle. It's like saying to do bicep curls to work your bicep, no ****. So the chest happens to be shaped in a unique way where the 2 muscles SQUEEZE together at full contraction. That's where that "inner chest" pressure comes from yeah? What about the rhomboids and traps? by this logic, the "inner" trap fibers would be stressed doing a reverse fly right? It's already sounding pretty ridiculous...

So the argument is, at FULL contraction, something makes the "inner" fibers work more than the "outer" fibers. I guess that applies to the biceps then? So at full contraction in a bicep curl, the "upper" fibers must be getting more work...somehow, by this magical theory.

Tilt the pelvis up to the sternum, it works the "lower" abs, but flex and bring the sternum to the pelvis and its "upper" abs. I can go on forever with examples, but I think i've given enough.

So, all the "cool books" that i've read are outdated, all the Neurophysiologists and Doctors are wrong, and have been teaching and believing old information. All the "bodybuilders" are right, because they did crossovers and their chest got bigger. Who would you want to explain Human Neuromechanics to you? A bodybuilder? Who would you want to explain the physics of playing pool? Jeannete Lee? or a Physicist?

Here's just a couple of links and quotes from recognized Doctors who believe what I (and many others) believe:

"the result of the "scientific evidence" that you speak of is based on an EMG tests measuring in millivolts (inconsistantly specific) and is sectionally specific to where it is placed on the muscle, but is not significant enough to cause a difference in levels of hypertrophy. this is especially apparant in muscles like the rectus abdominis which is divided by connective tissue which causes the muscle to "bead" as it contracts. all research reveals that there is no substantial localized contraction within the length of the fiber, even when divided by the fascia. this is sourced information from Dr. Stuart McGill and many other experts in neuromuscular transmission." -Dr. Stuart McGill

Here's probably the best one:
http://www.pubmedcentral.nih.gov/art...?artid=1189217

[i]" In the case of electrodes placed at compartment boundaries, no clear compartment selectivity of recording of motor unit potentials was evident. 6. These results indicate that great care must be taken in choosing sites of EMG electrode placement when performing kinesiological studies, especially when the amplitude of the EMG activity recorded is of consideration."

http://nsca.allenpress.com/nscaonlin...A%3E2.0.CO%3B2

"There were no significant differences (p > 0.05) between the EMG activity of the URA and LRA during any exercise. There were no significant interactions between subject and muscle site or between exercise and muscle site."

http://www.ncbi.nlm.nih.gov/sites/en...ubmed_RVDocSum

Thas more to do with fiber type, but touches on compartmentalization:
http://www3.interscience.wiley.com/c...TRY=1&SRETRY=0

"Therefore it seems that the compartmentalized organization of the FCR is not related to any specialized motor task, but may be a generalized pattern associated with motor patterns shared among all species studied."

Ok i'll spare the thousands of links about muscle contraction which are easily accessed on Google... to move on.



Here's the first link that Defiant1 lists, to try and prove his point:

http://icb.oxfordjournals.org/cgi/reprint/38/4/729.pdf

If you look at the part about "compartmentalization" you will see that they discuss the feline sartorius, a broad muscle with extended attachments, that inserts both onto the tibia, and the patellar ligament. the muscle activation varies depending on the ROM of the step for each part of this muscle, as it is fed to different innervations. Does the pec major work like this? OBVIOUSLY it does not. The other example was neck and trunk muscles, which attach in multiple slips to different vertebrae and ribs. Again with seperate innervations, this does not apply.

Defiant1's second link:
http://jap.physiology.org/cgi/content/full/99/3/1149

"We found that, in the MG, relative activated area in the distal portion of the muscle was larger than that in the proximal portion. This region-specific difference was consistent with the present EMG data, suggesting muscle activation is distributed unevenly along the length of the MG. The existence of such heterogeneity is reflected by the architecture of the MG muscle (18); the fiber pennation angles in the distal portion are significantly smaller than in the proximal portion. That there is a significant negative correlation between the specific tension and the fiber pennation angle (16) means that the distal portion of the human MG has a greater force-generating capacity."

FROM YOUR VERY OWN LINK!!!!!!

"The existence of compartmentalization within muscles has been demonstrated in the MG of the rat (8, 15), where there is a load-related activation differential between the proximal and distal compartments. On the other hand, direct dissection of cadaver specimens revealed no neuromuscular compartmentalization in the human MG (40)."

Next one:
http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract

Nothing but an abstract that generalizes the definition of compartmentalization and suggests that "muscles are complex"

Then a series of article from ABCbodybuilding and T-Nation.... no thanks.

I really dont know what else to say. If you want to twist a study done on a lab rat's medial gastrocnemius into "close grip bench works your inner chest fibers" then be my guest. Its absurd. And to think that there is even a remote possibility that you would gain any noticeable shape or hypertrophy in that specific region is even MORE absurd. The convenient part is that doing a chest specific exercise (crossovers) will make the chest larger, which in turn will "fill in the gap" and appear that the inner chest fibers grew. Yeah and one day we can all have a chest shaped like a pyramid, as long as we dont do any work for our "outer chest fibers"!!!!!!!

DISCUSS.

[schweefy]

I'm a 100% with you on this. When I first started training I thought that you could target the infamous inner chest with certain exercises as that's what I had heard. So of course I tried.... and failed.. and wasted a lot of time doing pointless exercises. Now I stick mainly to presses and leave CGBP to the triceps.
IMO, trying to target the inner chest is a waste of time and effort. Just focus on different angled presses and the growth will come.

[I dont work at Ballys]

Originally Posted by schweefy

I'm a 100% with you on this. When I first started training I thought that you could target the infamous inner chest with certain exercises as that's what I had heard. So of course I tried.... and failed.. and wasted a lot of time doing pointless exercises. Now I stick mainly to presses and leave CGBP to the triceps.
IMO, trying to target the inner chest is a waste of time and effort. Just focus on different angled presses and the growth will come.

Thank you for your input. CGBP is another great example, the brilliant logic of "the closer your hands are together, the more the 'inner chest' fibers are working."

and you're absolutely right, work the muscles from different angles, compounds, isolations, they all have their benefits.

[d_k]

This is a good thread, lookin for some good discussion on the issue

I'm not gonna lie, I'm not one with all the scientific knowledge behind all this.. I notice that my 'inner chest' feels bigger when I get a good overall chest pump from presses and fly's, but it could be just the bigger mountains making the crevice more noticable, you know?

[Sleepstream]

Originally Posted by d_k

This is a good thread, lookin for some good discussion on the issue

I'm not gonna lie, I'm not one with all the scientific knowledge behind all this.. I notice that my 'inner chest' feels bigger when I get a good overall chest pump from presses and fly's, but it could be just the bigger mountains making the crevice more noticable, you know?

When the chest is pumped, I believe it is easier to notice the inner chest difference since there is no muscle on the sternum. When you compare the outer portion of the chest, it pretty much goes into the anterior delts, so the muscle isn't as noticeable in that region.

But regardless, people are still going to continue to do their inner chest exercises because that is what they believe to be effective.

[Uriel_da_man]

Well you bet your ass I'll read all that, you just wait.

[I dont work at Ballys]

Originally Posted by d_k

This is a good thread, lookin for some good discussion on the issue

I'm not gonna lie, I'm not one with all the scientific knowledge behind all this.. I notice that my 'inner chest' feels bigger when I get a good overall chest pump from presses and fly's, but it could be just the bigger mountains making the crevice more noticable, you know?

Originally Posted by Sleepstream

When the chest is pumped, I believe it is easier to notice the inner chest difference since there is no muscle on the sternum. When you compare the outer portion of the chest, it pretty much goes into the anterior delts, so the muscle isn't as noticeable in that region.

Right, because of the way the muscles are arranged, the chest is by far the easiest example, and is why I used it as the main focus of the thread.

Originally Posted by Sleepstream

But regardless, people are still going to continue to do their inner chest exercises because that is what they believe to be effective.

and that is fine, I think its great that people want to do chest exercises to work their chest, whatever their motivation for doing it may be, I'm just trying to help people understand the way that the muscle works as it seems to be a very common n00b question here (and everywhere)

[Uriel_da_man]

Well I lied I'm not really gonna read all that

From what I did read, on the part of the EMG results being inconclusive because the differences are only millivolts, I think we should first clarify what range IS conclusive. What tension does make a difference, anyway? And are we talking about a difference in a matter of two workouts, or twenty?

[I dont work at Ballys]

Originally Posted by Uriel_da_man

Well I lied I'm not really gonna read all that

From what I did read, on the part of the EMG results being inconclusive because the differences are only millivolts, I think we should first clarify what range IS conclusive. What tension does make a difference, anyway? And are we talking about a difference in a matter of two workouts, or twenty?

LOL ok, well at least read this one real quick, it should answer your question: http://www.pubmedcentral.nih.gov/art...?artid=1189217

[TheGunShowMane]

I did some of 'A-trainer's flys' Yesterday, did about 8 sets, no other chest training so supposedly this would be an inner chest exercise, but my entire chest feels sore at the mo so I guess I would have 2 agree with experience.
Looking at the basic anatomy, you would have to say that it would be impossible to isolate growth from the inner chest as the fibres run the bredth of the rib cage.

[Uriel_da_man]

Real quick? o.O

[Defiant1]

Oh jeebus.

First.

EVERY COMPETITIVE BODYBUILDER THAT I KNOW AND HAVE EVER SEEN A ROUTINE FROM DISAGREES WITH YOU.

Plus, the vast experiences of decades of training go against what you are saying.

You are letting lack of measurement ability dictate your reality.

That is the starting point.

Now to address your specific points:

Originally Posted by Ballystrainer

I am not debating that the upper and lower portions of these fibers can be stressed by performing different chest exercises from different angles, I am stating that the muscle fibers cannot be stressed as they run the length of the muscle from its origin to insertion point. YES, I realize that a single muscle fiber does not run the entire length of a muscle, but it is connected to another muscle fiber and etc.. which runs to the opposite end, and these fibers will contract uniform to eachother IN RATIO which does not mean the EMG numbers will match but that they will in fact be relative to eachother.

The fact that you are saying this means you likely disagree with what you were taught wherever you learned your philosophy. I can assure you you were likely taught "contiguous innervation" in humans. Which is why I post GENERALLY about compartmentalization-it GOES AGAINST what is commonly taught. At least the last time I checked, and from the crap people say, it seems to still be spat out. FYI, "contiguous innervation" would say that the Lats are ONE MUSCLE FUNCTIONALLY. Do you actually believe that? It has basically been disproven.

So, in order to even CONSIDER what I am describing, one has to at LEAST believe in compartmentalization. Whether you know it or not, compartmentalization is a "radical" concept. And "upper/lower" chest is NOT compartmentalization. That is actually part of "contiguous innervation". But the catch is...so is "upper/lower abs"!!!!!!!!!!!!!!!!!!! No one except the most lab isolated monkey believes that one cannot emphasize parts of the abs.

Pec/Lat/Delt "sections"..
http://www.worldscinet.com/131/08/08...704001211.html

task dependency with lats:

http://www.ncbi.nlm.nih.gov/sites/en...&dopt=Citation

Seriously, does ANYONE that has ever done a crunch thinks it works your lower rectus? Please.

You seem to have adopted some weird "hybrid" philosophy from I don't know where.

If you believe in compartmentalization, you believe in being able to emphasize different parts of the rectus abdominus. No ifs, ands, or buts. If you say "no", then you need to stop even having this conversation.

Originally Posted by BT

COMPARTMENTALIZATION: The division of a single muscle into anatomical compartments each of which has its own primary nerve branch. Therefore, each anatomical compartment can be recruited independently and may function as a separate entity

Correct. and the amount of "compartmentalization" is far more vast than previous realized, for ALL muscles

The rectus abdominis has MULTIPLE INNERVATIONS, MULTIPLE INSERTION POINTS, AND MULTIPLE ORIGIN POINTS. Using the rectus to illustrate your position is idiotic.

Originally Posted by BT

and these fibers will contract uniform to eachother IN RATIO which does not mean the EMG numbers will match but that they will in fact be relative to eachother.

This is where this "questioning" falls apart. You are assuming that the evidence ONLY shows 1 consistently ratioed difference between proximal/distal portions in use. NOT THE CASE. I am talking about VARYING ratios that are TASK dependent. This is TOTALLY independent of that possibility of error you describe, which by the way was specific to the rectus (McGill). A useless argument, since NO school of thought believes this. Fred Hatfield is (or was) one of the staunchest "contiguous innervation" people I know of. Even HE acknowleges this.

Regardless..

[Sleepstream]

Originally Posted by I dont work at Ballys

and that is fine, I think its great that people want to do chest exercises to work their chest, whatever their motivation for doing it may be, I'm just trying to help people understand the way that the muscle works as it seems to be a very common n00b question here (and everywhere)

It's a good motivator for people to work their chest by focusing on the "inner chest". Most who I've seen do the inner chest exercises actually seem to be eliminating as much of the other muscles typically used in exercises. Pretty much a better "mind-muscle connection" as some call it.

[schweefy]

Originally Posted by Defiant1

Oh jeebus.

First.

EVERY COMPETITIVE BODYBUILDER THAT I KNOW AND HAVE EVER SEEN A ROUTINE FROM DISAGREES WITH YOU.

Plus, the vast experiences of decades of training go against what you are saying.

You are letting lack of measurement ability dictate your reality.

I was waiting for you to show up...

[schweefy]

I feel this thread has the potential for a sticky. I see it has already managed 5 stars.

[I dont work at Ballys]

Originally Posted by Defiant1

Pec/Lat/Delt "sections"..
http://www.worldscinet.com/131/08/08...704001211.html

task dependency with lats:

http://www.ncbi.nlm.nih.gov/sites/en...&dopt=Citation

I dont think you read my whole post.

the first link you provided merely states that the muscles are divided into different sections that are stressed differently from DIFFERENT LINES OF PULL.

the second link states that the EMG was taken ALONG THE ORIGIN of the lat, which obviously would show differences in upper/lower depending on the line of pull and position of shoulder as the lat inserts into the intertubercular groove, causing it to twist.

Interesting how most of your links either prove my point further or are quite subject to flaw and speculation...

[I dont work at Ballys]

Originally Posted by schweefy

I feel this thread has the potential for a sticky. I see it has already managed 5 stars.

I'm not concerned with that, but i am happy to finally get all my thoughts on "paper" so i can link this to people that bring up this topic.

[Defiant1]

Unless you read this (I can tell you haven't), you are not going to understand

http://www.ptjournal.org/cgi/reprint/73/12/857.pdf

It specifically addresses all of your points, including proximal v distal relative use (NOT a ratioed difference) and the exact mechanism of how this happens

Originally Posted by bt

So, all the "cool books" that i've read are outdated, all the Neurophysiologists and Doctors are wrong, and have been teaching and believing old information. All the "bodybuilders" are right, because they did crossovers and their chest got bigger. Who would you want to explain Human Neuromechanics to you? A bodybuilder? Who would you want to explain the physics of playing pool? Jeannete Lee? or a Physicist?

Here's just a couple of links and quotes from recognized Doctors who believe what I (and many others) believe:

"the result of the "scientific evidence" that you speak of is based on an EMG tests measuring in millivolts (inconsistantly specific) and is sectionally specific to where it is placed on the muscle, but is not significant enough to cause a difference in levels of hypertrophy. this is especially apparant in muscles like the rectus abdominis which is divided by connective tissue which causes the muscle to "bead" as it contracts. all research reveals that there is no substantial localized contraction within the length of the fiber, even when divided by the fascia. this is sourced information from Dr. Stuart McGill and many other experts in neuromuscular transmission." -Dr. Stuart McGill

You keep mentioning McGill, like he is the only one who knows how to use EMG....lol. The fact that someone CAN make a mistake, doesn't mean that every study involved has a mistake. STRONG non-sequitor.

Here's an even cooler quote, from someone who SPECIFICALLY studies EXACTLY what we are talking about...

Oh hai, and here are his creds:

B.S. Biology, The American University, Washington D.C.

M.S. Exercise Physiology, Kent State University, Kent OH

Ph.D. Skeletal Muscle Physiology, University of Texas Southwestern Medical Center, Dallas TX

Post-doc, Endocrinology and Metabolism, UT Southwestern Medical Center, Dallas, TX

Fellow of ACSM

Certified Strength and Conditioning Specialist

Chief Executive Officer of the International Society of Sports Nutrition

Board of Directors - National Strength and Conditioning Association (2005-08)


Another group of scientists examined how different heads of the biceps brachii muscle are activated during supination movements. If you?ve forgotten, supination is a movement that occurs around the radioulnar joint and occurs when you rotate your forearm such that your palms face up. And the biceps brachii is the primary muscle involved in supination! These scientists showed that when the elbow was flexed to 120 degrees, the short head (medial side) was activated more so than the long head of the biceps during supination. And the further the elbow was extended, the more the long head of the biceps came into play. Thus, if you want to stress the medial side of the biceps muscle, do supination movements at 120 degrees of flexion. Most gyms now have machines which allow isolated supination movements. So give it a shot; it?ll be a good addition to your arm workout.



Further evidence for the functional differentiation within the biceps muscle is magnetic resonance imaging which demonstrate that a standing bilateral dumbell curl with your palms up (supinated) hits the medial or short head of the biceps brachii muscle more so than the lateral or long head. On the other hand, doing the same exercise with a neutral grip (slightly pronated) results in better activation of the lateral or long head.



And what about the notion that you can train your upper vs. lower abs? Here?s an area where there is a big dispute concerning the role of the ab muscles. Many believe that the rectus abdominus is one muscle (which is correct) that is activated equally when you contract it (which is incorrect!). A study done at the University of Valencia in Spain compared the average EMG activity of the upper and lower abs during a curl-up and posterior pelvic tilt exercise. They found that it is true that the stomach crunch or curl does elicit greater rectus abdominus activity in the upper abs while doing posterior pelvic tilt exercises hits the lower abs better as long as they?re performed correctly!



We can even examine a small forearm muscle such as the extensor carpi radialis longus (ECRL) muscle. You?re thinking what the hell or where the hell is this muscle with a monstrously long name. The ECRL performs wrist extension and radial deviation (movement of the hand sideways towards the thumb). It originates at the lower end of the lateral surface of the humerus and attaches to the base of the second metacarpal. Even a muscle such as this is differentially activated depending on how you utilize it. For example, when you do wrist extension alone, the proximal ECRL is activated more so than the distal ECRL. However, when you do radial deviation, only the proximal ECRL is activated! The distal ECRL is in essence silent or inactive.





Notice MORE AND LESS, not just DIFFERENT BUT WITH THE SAME RATIO.

I guess Jose Antonio doesn't know how to read studiezorz!!L!L!L!L!L!L only Dr McGill can!!

[Defiant1]

Originally Posted by I dont work at Ballys

I dont think you read my whole post.

the first link you provided merely states that the muscles are divided into different sections that are stressed differently from DIFFERENT LINES OF PULL.

the second link states that the EMG was taken ALONG THE ORIGIN of the lat, which obviously would show differences in upper/lower depending on the line of pull and position of shoulder as the lat inserts into the intertubercular groove, causing it to twist.

Interesting how most of your links either prove my point further or are quite subject to flaw and speculation...

Interesting how you can't keep what you are saying straight.......

That school of thought is COMPARMENTALIZATION. Not "contiguous innervation"....

Do you not even know what you believe? "Upper/lower chest" is CONTIGUOUS INNERVATION, not "compartmentalization.

Are you confusedzors?

[Uriel_da_man]

I'll give it a 5 too, but probably not gonna read it when I come back tomorrow morning and find it 10 pages longer than I left it.

[Mark1T]

That was interesting reading, Bally's, and I can understand a little anyone that wants to base their training solely on studies such as these.

However, coming from the most elementary and simplistic point of view, many years ago I would experiment how various muscles would flex in various contractions. It is very elementary, but it does prove a point, to me. Ex: If you are sitting back in a 30 degree incline bench with no weight; raise one arm straight up, then flex inward toward the upper chest, you can feel with your other hand, that the top of the chest is tight and flexed. Then, you can feel the lower part of the chest as totally loose and unflexed. This tells me that Incline DB Presses would focus more on the upper chest region.

Ex 2: If you perform a one-arm cable crossover, so that your body is mostly upright with the handle movement going down to or below waist level, so that you are focusing on the lower inner-chest region, you can take your other hand and literally feel that the lower inner-chest region is being flexed, whereas if you feel the top of the chest, it is somewhat flexed, but not nearly as tight. This shows me that with proper form, you can focus on the lower inner-chest regions.

Granted, this is not scientific, but I would rather go by experience and actual results, rather than scientific studies that say I can't do it. One movement per muscle group could not work for me.

[Defiant1]

Originally Posted by BT

Then a series of article from ABCbodybuilding and T-Nation.... no thanks.

Nice avoidance, though I agree with not agreeing simply cutting and pasting everything under the sun.

but blindly disregarding something because of source is even worse.

Too bad the "T-nation" article is referenced, and discusses EXACTLY what we are talking about...

I don't mind posting so people can make their own decisions..

http://www.t-nation.com/portal_inclu...-training.html

Level 1: Muscle heads ? A lot of muscles are divided into separate portions or "heads." While these heads are part of the same general muscle group, they're actually semi-independent or independent and can have various functions. For example:

The chest includes: the sternal head of the pectoralis major (the big portion of the chest); the clavicular head of the pectoralis major (what's often called the "upper chest"); and the pectoralis minor (which is underneath the pectoralis major).

The delts include: the anterior head of the deltoid (front delts), the lateral head of the deltoids (side delts), and the posterior head of the deltoid (rear delts).

The quads include: the vastus lateralis (outer portion of the quads), the vastus medialis (the teardrop next to your kneecap), the rectus femoris, and the vastus intermedius.

The hams include: the short head of the biceps femoris, the long head of the biceps femoris, the semitendinosus (the long head and semitendinosus are the "meat" of the hamstrings), and the semimembranosus.

The biceps include: the short head of the biceps brachii (inner portion of the biceps) and the long head of the biceps brachii (outer portion of the biceps).

You get the picture.

Level 2: Fiber layering ? Studies have demonstrated that slow-twitch muscle fibers predominate in the deep portions of muscles while fast-twitch fibers predominate in the superficial portion of muscles. (Acosta et Roy 1986; Bredman et al.1990; Knight et Kamen 2005)

Level 3: Neuromuscular compartment ? This might be the most complex level of the subdivisions, but a lot of research backs it up. Neuromuscular compartmentalization refers to the division of the muscle fibers within a muscle group and their grouping in said muscle. Basically, muscle fibers are "bundled up" regionally into functional sub-units.

I'll get to the more complex scientific stuff later on, but let's start with an analogy which explains this theory. Imagine that one of your muscles (or one head of the muscle) is a city and that the highway leading to that city is the motor nerve (the motor nerve is what sends the motor command from the CNS to the muscle).

Now according to the "old" muscle recruitment theory, the command sent by the motor nerve would activate all portions of the muscle equally. In other words, it would be like the highway only having one exit toward the city. This theory has been proven to be erroneous. It was first postulated because "most studies of human muscle have not taken into account the possibility of partitioning beyond the grossly visible anatomical divisions." (English et al. 1993)

In real life, it's been shown that the motor nerve (highway) branches out into many smaller nerves which actually innervate different "sectors" of a muscle. See the picture below. (Be gentle, it took me hours to create!)



As you can see, the city (muscle) is divided into three separate portions. (These aren't "muscle heads." The city should actually be seen as a muscle without separate heads or a specific head. Partitioning means that there's a level of subdivision even beyond heads.) There's one big highway (motor nerve) leading to the city and this highway branches out into three separate exits (secondary motor nerves) each leading to one neighborhood of the city.

So as you can see, it's possible to send more traffic to one part of the city, just like the CNS can send a stronger activation signal to certain regions of a muscle.

Now, we can mix the first level of division (heads) and the third level (neuromuscular compartments) to further illustrate the point. We'll once again use our city as an example.



This map shows a region which has four towns, all in close proximity to each other. As you can see, the highway leads to each of these towns and some of them actually have more than one exit leading to it (not representative of the actual number of neuromuscular compartment of the muscles).

So, more traffic can go to one city or another. Within each city more traffic can also be sent to different neighborhoods, just like when you're performing an exercise for the quads, more stress can be placed on one of the four portions of the muscle as well as on individual sections of each portion of the muscle group.

Another way of explaining this level of division is the electrical current within a house: it all comes from the same source, but once it enters the house it's divided into several directions going to all the rooms. We can thus light up one room without having to light up the whole house. It's also possible to turn on only one electric apparatus in a single room. Same thing holds true with our muscles.

Okay, back to our scientific chit-chat! The analogies above give us an overview of the neuromuscular compartmentalization theory of muscle architecture.

So to recap, each muscle is innervated by a single motor nerve. As this nerve enters into the muscle, it branches out (divides itself) and goes to different regions of the muscle. (English et al. 1993) Therefore each of these regions, while synergistic (in most cases), are actually independent of each other. Why is that? Because of the function of the muscle as well as its fiber type distribution.

If you look at the anatomy of a muscle you'll notice that not all fibers are running in the exact same direction. Take the pectoralis major, for example. We can see several different lines of force gradually going from inward and up to inward and down.



This is a good indication that the muscle is divided into different compartments. The muscle is built this way to allow for a better control of movement: "Differential activation of motor units in different compartments may be a means of regulating the direction of the overall force application." (Bonasera et al. 1992)

[Defiant1]

cont:


Our pectoralis major plays an important role in bringing the arm toward the midline of the body. If we're trying to bring our upper arm from a "high and lateral" position (beginning of a crossover exercise for example) to a "low and medial" position (end of a crossover exercise), doesn't it stand to reason that the fibers which are actually oriented in that particular direction will play a larger role in the movement than the fibers going inward but up? I'm not saying that only the lower portion of the pectoralis will contract, but it will play a bigger role in the movement.



If we were to perform an exercise where the "height" of the arm doesn't change but where you're bringing it toward the midline of the body, the line of force will be parallel to the floor. So doesn't it also stand to reason that the fibers oriented along that line will perform more of the work?



Finally, if you were to perform a crossover from the low pulley, starting with the arms "low and lateral" and lifting them "high and medial," the line of force would be angled upwards and inwards. So for one last time, wouldn't it be logical to assume that the fibers oriented along the line of force would be more mechanically advantaged to perform the work and thus would receive more stimulation?



Fiber type is also important in neuromuscular compartmentalization. Understand one important physiological fact: an alpha motoneuron (the secondary motor nerve that's branched out from the main motor nerve) innervates muscle fibers of only one type. (Burke et al. 1973)

In other words, a secondary motor nerve (the exit from our map or the electrical wiring going to one room) will be linked to only one type of muscle fiber (Type I, Type IIa, or Type IIb). This kind of distribution allows the body to better modulate the amount of force to produce. Since we've already seen that the superficial portion of a muscle is predominantly fast twitch dominant and that the deeper portions are the opposite, this once again shows us that each muscle is actually divided into more independent compartments.

In truth, if you forget about the old-time dogma of muscle structure and look at it from a logical standpoint, you'll see that muscle subdivision is not only possible, it's a fact and it's necessary for proper mechanical functioning. However, I know that a lot of guys live to make fun of us writers and are quick to point out the flaws in our articles, so here are some tidbits from the literature on the subject:

[I dont work at Ballys]

LOL!!!!!!

the first study, done on the Biceps (2 heads) just talked about stressing the 2 heads, which is NOT what the debate is about at all.

here are 2 links that I posted in the first post that I think you "skipped over" that deal with upper/lower RA

http://nsca.allenpress.com/nscaonlin...A%3E2.0.CO%3B2

http://www.ncbi.nlm.nih.gov/sites/en...RVAbstractPlus

[Uriel_da_man]

This will probably be my last input before the mile-long replies and quotation groups take over and it gets painfull to look at.

I won't post any studies. To be honest I haven't read any studies in over a year. I won't make a fancy text, my english is feeling pretty lazy and I don't feel like using the dictionary. I'll simply post my own experience:

I have compared the shape of my pecs in periods of "basic" training (incline and flat bb presses and dips) vs periods with focus on "shape" (usually one or two meat builders with the said incline bb presses being the most common, and then cable flies, dumbbell presses and machine presses in various combinations) and always found that my outter pecs grow better from the basic training, but I NEVER get that cool "cleavage" between my pecs. You COULD blame this on genetics...if it weren't for the fact that when I do the "shape" training I manage to get a little of that cleavage WITH MINIMAL GROWTH ON MY OUTER PECS. So my conclusion, and the only logical one I see, is still: the basic training gives me the great majority of the growth on my outter pecs, while when I do shape training I get growth more distributed over the length of the muscle belly, therefore I do shape my pecs, by growing them in different proportions in distal vs proximal regions.

I think everyone should give this a try before trying to let these debates decide for them. Bally's, why don't you do six weeks of barbell pressing alone (preferably with wide grips), and then do six weeks of machine presses and cable flies and alike, always with lifts that "squeeze" the pecs, and simply see for yourself?

If you truly believe that you can't shape a muscle, then this wouldn't be any setback to you as you'd experience the same growth from both protocols, so why don't you just give it a try?

[Defiant1]

con't

1) "Variability in force direction within one and the same muscle has been suggested to be an important function of muscular compartmentalization." (Herring et al. 1979)

"Motor units in complex muscles have different lines of action and may have different functions." (Turkawski et al. 1998)

This means that the subdivision of each muscle into different subunits with varying lines of force allows the muscle the capacity to produce force in more directions.

2) "On the basis of muscle architecture, three regions were identified within the semimembranosus. Semitendinosus comprised two distinct partitions arranged in series. In the biceps femoris long head, two regions were supplied via a primary nerve branch divided into two primary branches. Biceps femoris short head consisted of two distinct regions demarcated by fiber direction with each innervated by a separate muscle nerve." (Woodley and Mercer 2005)

This means that the hamstring muscle group can actually be divided into nine different regions instead of the four originally thought. This is a prime example of subdivision within a certain muscle group.

3) "Electromyographic data indicates that there is a selective recruitment of different regions of a muscle that can be altered, depending on the type of exercise performed. ... muscles adapt in a regional-specific manner." (Antonio 2000)

This explains that not only are the muscles divided into specific regions, but that one can put more growth stimulus on one particular region via a change in exercise selection.

4) "Motor units may not be randomly distributed throughout the muscle but confined to localized sub-volumes." (Hammond et al. 1989)

5) "Just because something goes against what you personally believe doesn't mean that it's not true." (Christian Thibaudeau, 2006)

Level 4: Fiber segmentation ? Each fiber within a muscle runs from its origin right to its insertion. In other words, every muscle fiber spans the entire length of a muscle, right?

Wrong! Recent research has shown the opposite to be true in most cases. Muscle fibers are actually segmented and joined with other muscle fibers/segments to form a long ensemble that will eventually link both attachments together. Both ends of the connected muscle fiber segments are joined together via a collagen bridge or myotendinuous junction (the latter serving to pass tension from one segment to the next). (Hijikata et al. 1993, Young et al. 2000)

Furthermore, it seems that each strip/segment of a muscle fiber is selectively linked to its own set of motor axons. (Paul 2001) This means that not only are muscle fibers really divided into shorter segments aligned in series, but that each segment has its own source of activation.

The following image will help us understand all this. Understand that the picture is just an oversimplification, but for our objective it'll be sufficient.



This certainly doesn't mean that we can isolate only a few of those segments via exercise selection. However, it does show us that depending on the range of motion, anatomical position, and line of action of a movement, it's possible that certain segments will be placed under a greater tension and thus will undergo a greater amount of damage, which in turn could cause more hypertrophy to occur on certain portions of the muscle.

[Defiant1]

Originally Posted by I dont work at Ballys

LOL!!!!!!

the first study, done on the Biceps (2 heads) just talked about stressing the 2 heads, which is NOT what the debate is about at all.

here are 2 links that I posted in the first post that I think you "skipped over" that deal with upper/lower RA

http://nsca.allenpress.com/nscaonlin...A%3E2.0.CO%3B2

http://www.ncbi.nlm.nih.gov/sites/en...RVAbstractPlus

I've seen them. It's the same stuff.

As I said, arguing about the rectus being functionally differentiated is the WORST way to try to prove your point, since the fact that you agree with "upper/lower" pecs, and the mechanism (hint: it's not line of force, it is innervation), means you must agree that the rectus is functionally differentiated.

Can't have it both ways.


Did you see this?

And what about the notion that you can train your upper vs. lower abs? Here?s an area where there is a big dispute concerning the role of the ab muscles. Many believe that the rectus abdominus is one muscle (which is correct) that is activated equally when you contract it (which is incorrect!). A study done at the University of Valencia in Spain compared the average EMG activity of the upper and lower abs during a curl-up and posterior pelvic tilt exercise. They found that it is true that the stomach crunch or curl does elicit greater rectus abdominus activity in the upper abs while doing posterior pelvic tilt exercises hits the lower abs better as long as they?re performed correctly!



Does Antonio (see creds above) not understand your thinking?

Or, is it possible your thinking is outdated.

[I dont work at Ballys]

Originally Posted by Mark1T

That was interesting reading, Bally's, and I can understand a little anyone that wants to base their training solely on studies such as these.

However, coming from the most elementary and simplistic point of view, many years ago I would experiment how various muscles would flex in various contractions. It is very elementary, but it does prove a point, to me. Ex: If you are sitting back in a 30 degree incline bench with no weight; raise one arm straight up, then flex inward toward the upper chest, you can feel with your other hand, that the top of the chest is tight and flexed. Then, you can feel the lower part of the chest as totally loose and unflexed. This tells me that Incline DB Presses would focus more on the upper chest region.

Ex 2: If you perform a one-arm cable crossover, so that your body is mostly upright with the handle movement going down to or below waist level, so that you are focusing on the lower inner-chest region, you can take your other hand and literally feel that the lower inner-chest region is being flexed, whereas if you feel the top of the chest, it is somewhat flexed, but not nearly as tight. This shows me that with proper form, you can focus on the lower inner-chest regions.

Granted, this is not scientific, but I would rather go by experience and actual results, rather than scientific studies that say I can't do it. One movement per muscle group could not work for me.

thanks for your input. I am by no means saying to only do 1 exercise per muscle group. Again let me clarify that your first example is proven without a doubt and many compound movements affect muscles in different ways. different grips, lines of push/pull, rotations, partial ROM on compound movements, all affect the different portions of a muscle.

for your second example, the muscle gets shorter as it contracts, so it balls up, just like any other muscle, but the chest is a very good example of this. of course the inner portions gets bigger, so does the center though, and so does the rest of the muscle. touch the biggest part of your bicep with an outstretched arm, then flex, and bring the arm in to a full flex. it got bigger...same principle here.

[I dont work at Ballys]

DEFIANT i'll ask you nicely not to post the entire text of your links in this thread, everyone has the ability to click on a link.

please delete that and take excerpts to quote and use your own words to discuss. I encourage the discussion but theres no need for that.

[Defiant1]

Originally Posted by I dont work at Ballys

LOL!!!!!!

the first study, done on the Biceps (2 heads) just talked about stressing the 2 heads, which is NOT what the debate is about at all.

here are 2 links that I posted in the first post that I think you "skipped over" that deal with upper/lower RA

http://nsca.allenpress.com/nscaonlin...A%3E2.0.CO%3B2

http://www.ncbi.nlm.nih.gov/sites/en...RVAbstractPlus

Oh, and by the way, from your study about the RA:

Normalizing the EMG signal led the authors to believe that the differences between the portions of the rectus abdominis muscle are small and may lack clinical or therapeutic relevance.



And from Antonio:

just because something is not statistically significant does not mean that it isn’t physiologically significant.