Muscle Section Isolation

[maverick]

I know many here do not believe that you can shape a muscle, that its shape is predetermined by your genetics and that because you can't change insertion points, you can only make a whole muscle grow, not specific parts. I always tended to disagree with that based on gut feeling. I mean, if I do incline flies after DB presses, my upper chest is aching and on fire. If I do concentration curls before BB curls, I feel a distinct targetting on the peak of my biceps.

Here are some interesting excerpts from a study by Dr. Jose Antonio, "Nonuniform response of skeletal muscle to heavy resistance
training: Can bodybuilders induce regional muscle hypertrophy?" I'm not telling anyone to change their minds or dismiss what they believe to be true, just to consider what the article puts forth. I thought it was some pretty great stuff.

Skeletal muscle is a complex tissue that shows a prodigious capacity for growth. The notion that an individual muscle is just a compilation of muscle fibers that traverse from origin to insertion is simplistic and egregiously flawed. There are obvious differences between muscles with regard to size, architecture, and fiber composition. Moreover, within the same muscle, one can find regional differences in fiber size and fiber composition. Within a single fiber, one can find differences in MHC isoform expression and diameter.

Thus, it would make sense that the response of skeletal muscle to resistance training would be a nonuniform hypertrophy. In fact, the idea that a muscle would respond in a uniform fashion would seem implausible in light of the fact that there are distinct physiological/anatomical differences within a single muscle.

An individual muscle is more than just a collection of muscle fibers spanning the entire muscle belly with a single muscle–nerve interaction. Instead, a muscle can be divided into neuromuscular compartments, which are distinct regions of a muscle, each of which is innervated by an individual nerve branch and therefore contains motor unit territories with a unique set of characteristics. In other words, different portions of a muscle may be called into play depending on the task demands of the situation(

It would seem plausible that different exercises would stress different parts of muscle fibers. Perhaps this could alter gene expression within that particular myonucleus, resulting in the expression of particular MHC isoforms. Nonetheless, it is evident that skeletal muscle is heterogeneous between muscles, within a muscle, and within single muscle fibers( 39 ).

Interestingly enough this statement about expressing particular mhc isoforms( which again hinges on the fact that several muscle fibers have been shown to have type IIA, IIB, and type I combinations within them! )of a muscle fiber has been shown through studies as well. In fact Klitgaard, H., M. Zhou, and E.A. Richter in 1990 using bodybuilders as participants showed decreased coexpression of fibers with IIA/IIB combination fibers then compared with sedentary individuals( 49 ) and this was also duly noted in a similar study on the quadriceps in 95( 48 ). Furthermore Antonio also states:

The notion that a particular resistance exercise will cause the entire muscle belly to grow in a uniform manner is at odds with the fact that muscles and muscle fibers are themselves heterogeneous( 39 ).

[threenorns]

that just says that different parts of the muscle fibre react in different ways and are different sizes. it doesn't say anything about neurotransmission - a signal fires at one of the neuron and activates it. if needed, the signal is also emitted from the other end of the neuron in order to activate the next in line. therefore, the muscle is digital - "on" or "off". different parts of the muscle will react differently according to physiology, but you can't specifically target, say, the larger size fibres at the belly of the muscle and make them fire differently from the rest of the muscle body.

obviously, the muscle fibres are NOT homogenous, or there'd not be the wide variation on bicep shapes, that's obvious. but that doesn't mean, ipso facto, that you can change the actual conformation of the muscle.

[.V.]

Interesting reading maverick - and EXACTLY why I finish up my chest day by wasting time on decline bench presses.

Perhaps it isn't going to happen the way I want it to, but my sad little chest is lifting a bit from the bottom - better than being droopy like it was before...OK, it's still droopy, but better.

[armorforsleep]

Originally Posted by threenorns

that just says that different parts of the muscle fibre react in different ways and are different sizes. it doesn't say anything about neurotransmission - a signal fires at one of the neuron and activates it. if needed, the signal is also emitted from the other end of the neuron in order to activate the next in line. therefore, the muscle is digital - "on" or "off". different parts of the muscle will react differently according to physiology, but you can't specifically target, say, the larger size fibres at the belly of the muscle and make them fire differently from the rest of the muscle body.

obviously, the muscle fibres are NOT homogenous, or there'd not be the wide variation on bicep shapes, that's obvious. but that doesn't mean, ipso facto, that you can change the actual conformation of the muscle.

let me give you my understanding, if i am wrong please correct me

what you say is true- however you are missing a critical fact. you are assuming basically that a muscle is basically one fiber (maybe a large one). say, the bicep muscle. but there are many muscles in the biceps alone (there are ~650 muscles total in the body). while you cannot change the shape of an individual one, you can change the shape of the whole "muscle" ie the bicep, by using specific exercises that require innervation of certain parts of the bicep.

[Firehawk]

How can you target certain parts of one muscle? That makes no sense. Either the fibers fire or they don't, thee end.

In the chest there is another muscle besides the pec that runs across the top. that's probably what mav feels getting worked when he does incline bench and feels the DOMS.

[SNPiccolo5]

Originally Posted by Firehawk

How can you target certain parts of one muscle? That makes no sense. Either the fibers fire or they don't, thee end.

In the chest there is another muscle besides the pec that runs across the top. that's probably what mav feels getting worked when he does incline bench and feels the DOMS.

I think the article is just saying that since there are many different fibers/types of fibers in a muscle, and since they play different roles, it may be possible to target different parts of a muscle. Sort of like sub-muscles?

Seemed interesting... I really haven't formed an opinion on this, I guess...

-Tim

[Firehawk]

Well you can try to target different types of fibers but you dont' ever really know what you're targetting when ur lifting weights and who the hell would know the distribution of where a fast twitch fiber is or a slow twitch without dissecting it?

[armorforsleep]

Originally Posted by Firehawk

How can you target certain parts of one muscle? That makes no sense. Either the fibers fire or they don't, thee end.

In the chest there is another muscle besides the pec that runs across the top. that's probably what mav feels getting worked when he does incline bench and feels the DOMS.

every exercise is different - so cable curls cause innervation of a different set of bicep muscle fibers than barbell curls.

what you are referring to in your chest example is the two different heads in the chest muscle group - the sternal and clavicular heads. but in my argument i break it down further - there are maybe 70 different muscles in the chest not just 2.

[threenorns]

there can be two heads or twenty - the muscle fires and that's it - it's not a variable thing.

the muscle firehawk is referring to is the pectoralis minor - the one ppl focus on is the pectoralis major (the pecs).

the pectoralis major brings the upper arm bone across the chest. the pectoralis minor shrugs the shoulder area forward, which is why the different feeling when doing dips vs flyes or press.

[maverick]

Originally Posted by threenorns

there can be two heads or twenty - the muscle fires and that's it - it's not a variable thing.

But from what you said above:

Originally Posted by threenorns

that just says that different parts of the muscle fibre react in different ways and are different sizes.

muscle fibers can react differently. As a muscle is composed of separate muscles fibers, why is it hard to believe that you could shape a muscle with the proper stimulus on specific fibers. You stated that a fiber's response was "digital", yes or no, so it is limited to either growing or not growing. But this is the basis for complex systems capable of change beyond its smallest components needs. I mean, look at a computer. At its most basic units, all it is is yes and no. I don't think I need to get into what endless possibilites were created rom that.

[Firehawk]

But you are assuming that certain types of muscle fibers are located only in certain areas of the muscle are you not?

[armorforsleep]

Originally Posted by maverick

But from what you said above:



muscle fibers can react differently. As a muscle is composed of separate muscles fibers, why is it hard to believe that you could shape a muscle with the proper stimulus on specific fibers. You stated that a fiber's response was "digital", yes or no, so it is limited to either growing or not growing. But this is the basis for complex systems capable of change beyond its smallest components needs. I mean, look at a computer. At its most basic units, all it is is yes and no. I don't think I need to get into what endless possibilites were created rom that.

I totally agree Mav. The whole all-or-nothing event in the nervous system in relation to neuromuscular innvervation is, I think, one of the most misunderstood things in physiology. here is an excellent analysis http://www.abcbodybuilding.com/anatomy/allornone.htm

[maverick]

Originally Posted by Firehawk

But you are assuming that certain types of muscle fibers are located only in certain areas of the muscle are you not?

I guess, in a sense. I'm not going to claim to be a physiologist, but we know that certain muscles are composed of differing ratios of the differnt types of muscle fiber. If the predominant location of slow twitch muscle fiber in a particular muscle is known, woudln't it be possible to emphasize that section with high rep exercise? If a certain stance for squats, toes way out for example, creates increased tension and stretch on the part of the quad directly above the knee, why wouldn't it incur more muscle damage and hence more growth? And why do I feel the DOMS specifically in that area of the muscle (last week I did exactly what I mentioned in the last 2 sentences)?

Nice article armorforsleep, I plan to read it in full tonight.

[threenorns]

read the article.

"good" is not a word i would choose.

excessively technical and poorly written, would be better.

i'm still having trouble figuring out what he's talking about, since there is no conclusion.

Larry Scott at 24 and 64
You can change the stimulation that a muscle receives by using different angles. Larry Scott, when he was younger and doing lots of preacher bench curls, had what are commonly described as football shaped biceps. After he got older he changed his workout to include more "peaking" style exercises and now sports a very nice peak to his biceps. How else can you explain this change other than varying the muscular stimulation?