Muscle Shape

[iron addict]

This thread was by Instynct over on Animals board


Someone asked me a question regarding localized specific growth of a region of a muscle using the inner pecs as an example so i figured i would share the response here since many are not aware of these dynamics and have misconception and undertstandings in this area...so i figured i would also give it a title,LOL
Firstly, here was the question that inspired my little diatribe...

Hello, friend.

We have a discussion over at a norwegian board, where some asshole IFBB PRO claims one can isolate the inner chest, with training benchpress with a smaller grip. I`ve tried to find evidence against it (such as magnetic images, but haven`t been able to find them). Anyway, Ive discussed it with some of the bigger authorities and they are in fact insecure.

I see it like this;
there is no possible method of isolating the inner chest from the outer chest. If you take an anatomy class you'll learn that there is no distinction between the two. Then just apply basic physics...
If you hang a rope from a bar and tie a weight plate to the bottom of that rope, which part of the rope holds most of the weight? No part. The force (tension) pulling down the weight is equal throughout the rope. No part of the rope is strained more than any other part. It is the same with muscle fibers. You cannot isolate the inner chest from the outer chest, the upper bicep from the lower bicep, etc etc. It may appear that some people, as they become more advanced, develop more in the "inner chest" towards the sternum. HOwever, the reality is that this comes from two things: overall increased muscle size and lower bodyfat % levels.

Please give me your opinion. Thanks in advance,
Hardway


Muscle Shape...It's In The Genes...So Deal With It!
By Dave Douglas


It's a question of unsure conjecture for a long time now.
Theoretically, biomechanically there is no way for the pectoralis muscles to contract separately from any portion and when a muscle contracts the whole muscle contracts as far as what is simply seen as the contraction. BUT, there may be a greater innervation of contractile proteins within the region that is being targeted as when a muscle contracts there is not 100% neuromuscular efficiency and the signal for the actual fibers that are receiving innervation may be possibly localized as a greater percentage of firing neurons within the framework of that muscle. However of course even individual bundle must assuredly contract as a whole, but the contractions force can be derived more dominantly by that innervated portion to bring the full muscle fiber bundle into contractile state. There also seems little doubt that one does in fact feel a great sense of muscular exhaustion and/or 'burn' localized in the inner portion of the pectoralis when doing close grip pressing movements. What I think is the MAIN!!! point of practicality here is the notion that individuals can change the predetermined genetic shape of their muscle such as bringing out the peak of a bicep or a fuller inner chest. This through years of observation i know to be wholly untrue as the body has such a strong predetermination of set muscle structure, insertion, and myofiber density that all the 'targeted' exercise in the world will do little to alter this. Furthermore, it is even hard to bring up lagging bodyparts as the body has sharply determined its pre-existing structure and propensities and unless a bodypart was specifically neglected and that is the reason it is lagging, it will usually not be able to brought much further into proportion with the rest of the physique than it already exists.

Anyway, back to the 'targeting' of a specific portion of a muscle as this may help explain some of what i propose above.
All motor neurons leading to skeletal muscles have branching axons, each of which terminates in a neuromuscular junction with a single muscle fiber. Nerve impulses passing down a single motor neuron will thus trigger contraction in all the muscle fibers at which the branches of that neuron terminate. This minimum unit of contraction is called the motor unit.
The size of the motor unit is small in muscles over which we have precise control and larger in ones that require less complex movement. A single motor neuron triggers fewer than 10 fibers in the muscles controlling eye movements and the motor units of the muscles controlling the larynx are as small as 2–3 fibers per motor neuron. In contrast, a single motor unit for a muscle like the gastrocnemius (calf) muscle may include 1000–2000 fibers (considered to be largely scattered uniformly through the muscle at one time but upon closer examination are not so.).
Although the response of a motor unit is all-or-none, the strength of the response of the entire muscle is determined by the number of motor units activated. This is key in indicating the potential for specific portions of the muscle to perhaps being more greatly innervated and to thus provide the greater portion of the contractile force of the muscle and hence they are worked more dominantly. The negation though of this thought is that the motor units are uniformly scattered through the muscle and thus if that is indeed so then it is impossibly for a specific portion of a muscle like the pectoralis to contract as the smallest unit of contraction, the motor unit, innervates fibers uniformly throughout the muscle. Only if someone were to display that a motor unit had a dominantly proportioned density of fibers in a specific area such as the inner portion of the pectoralis could the targeting theory be correct. Well such has been done numerous times. Studies have confirmed the existence of neuromuscular compartments. One compartment is a "portion" of a muscle which is supplied by a particular nerve branch. This compartment contains, in many cases, motor units with distinct functions. Further, the number of muscle fibers in a neuromuscular compartment varies. Van Zuylen et al.(1988) explains by stating that, "Most muscles are not activated homogeneously; instead the population of motor units of muscles can be subdivided into several subpopulations." As wel he states” "… motor units in muscles are not necessarily activated if their mechanical action contributes to a prescribed torque. For example, there are motor units in the medlial biceps that are activated during flexion torques, but not during supination torques.” Thus one can see that the complexity and innervation of muscle can indeed exhibit localized dominance due to the lack of homogeny and furthermore there is other evidence for even greater specificity of localized effect to the cells themselves. But, also remember again, in regard to physique structure the overall dominance appears to be guided by predetermined genetic factors that are near impossible to overcome to any great degree. Those who have thicker inner chests have a pretermined propensity for that structural hypertrophy to occur for instance. The same hols true for peaked biceps, et. al., and yes, of course those who are more maximally hypertropied will usually have more pronounced characteristocs than those less so (generally) which is due to the development of the potential allowed by their genetics and not by training specificity by and large...although i am not saying it plays absolutely no factor, just minimally so and far less than most believe within general perception. Thus one can through training target innervation ‘compartments’ perhaps more specifically, but hypertophy will largely not be affected as it is more a function of fiber density and shape as to changing the shape of a muscle. Simply note even in totally separate bodyparts that some may have severely lagging calves, but amazing arms…not due to any lack of training or innervation, but due to lack of fiber density/type in the area. The same holds for areas of a muscle where some may have very poor fiber density and type in their inner pectoralis and/or pectoralis-deltoid insertion and others have a very full complete and thick chest all around due to excellent density exhibited uniformly through the entire pectoralis. Thus through training one will bring out superior shape in the muscle generally just by hypertophy and realizing potentials of the genetic structure and desnity, BUT, the potentials largely can not be altered to any signifiant degree through training specficity for localized growth.

[Desp]

That's pretty interesting, what was the answere though? It didn't have enough paragraphs.

[iron addict]

What ya got is what ya got. You can make it much bigger, but shape shifting ain't gonna happen.

IA

[Desp]

Cool thanks, that's what I thought he was saying.

[dutch]

Damn so all the effort lately to develop a arnold like bicep peak with my concentration curls and peak contraction are not gonna give me alp like biceps....