Bodybuilding.net - Bodybuilding Forum

_Wolf_ · #1 04-15-2006, 04:37 AM

Originally Written by Robert DiMaggio

Isolating the upper, middle and lower pecs (chest)
This is a very common question and debated topic, personally I believe that it is not possible to isolate any part of a single muscle, i.e. the pectorial major.

The following "article" explains in great detail why this is not possible. Credit goes to Belial from another board (I do not know his real name).

Quote:

The existence of the so-called "upper", "lower", "inner" and "outer" pectorals along with the assertion that it is possible to isolate one or more of these to the relative exclusion of the others in training, are among the most firmly entrenched myths in Strength Training and Bodybuilding circles. In fact none of these truly exist as either separate and distinct muscles or regions in a functional sense. Even though it could be argued that there appears to be a structural distinction between the upper and lower pectorals (and some anatomy texts do in fact support this distinction though not all do) because the pectoralis-major does originate from both the sternum and the proximal or sternal half of the clavicle along it’s anterior surface (it also has connections to the cartilages of all the true ribs with the frequent exception of the first and seventh, and to the Aponeurosis of the external oblique muscle), this is considered to be a common (though extensive) origin in terms of the mechanical function of the muscle. Thus the pectoralis-major is in fact for all practical purposes one continuous muscle with a common origin and insertion, and functions as a single force-producing unit. The terms upper, lower, inner and outer are imprecise and relevant only in order to make a vague subjective distinction between relative portions of the same muscle for descriptive purposes. They are vague and imprecise terms because there is no clearly delineated or universally defined border between them.

Further it is not physically possible either in theory or practice to contract one region of a single muscle to the exclusion of another region or regions (as a Biomechanics Professor of mine once demonstrated to a bunch of us smart-ass know-it-all’s taking his course, using EMG analysis). When a muscle contracts it does so in a linear fashion by simultaneously reducing the length of its constituent fibers and thus its overall length from origin to insertion. Even where a single muscle is separated into multiple functional units that are clearly defined such as the triceps (which are referred to as “heads” by Anatomists and Biomechanists), because they share a common point of insertion in order for one head to shorten all must shorten. This only makes sense if you think about it because otherwise there would be “slack” in one when the other shortened, which as we know does not occur. Note that there are some special cases where one head of a muscle must actually lengthen when the other shortens (e.g. the posterior head of the deltoid in relation to the anterior head during the positive stroke of fly’s), the point however is that even in these special cases there is no “slack” because there is in fact contractile activity (whether concentric or eccentric) throughout the muscle.

That is not to say however, that all fibers in different areas, or heads are necessarily shortened to the same degree during a particular movement. Depending on the shape of the muscle, the joint geometry involved, and the specific movement being performed, fibers in one area of a muscle or head may be required to shorten more or less than in others (or even to lengthen) in order to complete the required movement. For example during a decline fly though muscle fibers in all regions of the pectoralis-major must shorten as the upper arm is drawn towards the median plane of the body, because of the angle of the arm in relation to the trunk the fibers in what we commonly refer to as the lower pecs will have shortened by a greater percentage of their overall length than those in the upper region of the muscle by the completion of the movement. Conversely when performing an incline fly there is greater shortening in the fibers towards the upper portion of the muscle than in the lower.

Many proponents of the so-called “isolation” approach to training claim that this proportionally greater shortening of the fibers equates to greater tension in the “target” region than in others, and therefore stimulates greater adaptation; but this is completely at odds with the cross-bridge model of muscle contraction which clearly shows that as fiber length decreases tension also declines due to increasing overlap and interference in the area of the cross-bridges. Some also contend that the fibers called upon to shorten to a greater degree tend to fatigue faster than others and that therefore there is greater overall fiber recruitment in the region where this occurs, and thus a greater stimulus to growth; but there is no evidence to suggest that a fiber fatigues faster in one position than in another in relation to other fibers in the same muscle. In fact it has been shown that Time Under Tension (TUT) is the determining factor in fatigue and not fiber length. In fact fiber recruitment tends to increase in a very uniform fashion throughout an entire muscle as fatigue sets in.

The ability to “isolate” a head, or region of a muscle to the exclusion of others by performing a particular movement, or by limiting movement to a particular plane and thus develop it to a greater degree, is a myth created by people who wish to appear more knowledgeable than they are, and has been perpetuated by trade magazines and parroted throughout gyms everywhere. It is pure non-sense and completely ignores the applicable elements of physiology, anatomy, and physics in particular. Quite simply the science does not support it, and in most cases is completely at odds with the idea.
Regardless of the science however, many people will remain firmly convinced that muscle isolation is a reality because they can “feel” different movements more in one region of a muscle than in others. This I do not dispute, nor does science. There is in fact 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. However this has to do with proprioception (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) and not tension, fatigue, or level of fiber recruitment. Unfortunately it has been seized upon and offered up as “evidence” by those looking to support their ideas by any means available.

Muscle shape is a function of genetics and degree of overall development. As you develop a muscle towards its potential, it does change in appearance (generally for the better) but always within the parameters defined by its inherent shape. A person who tends to have proportionately more mass towards the upper, lower, inner or outer region of his or her pectoralis-major will always have that tendency, though it may be more or less apparent at various stages in their development, and in most cases appears less pronounced as overall development proceeds. That is not to say that training a muscle group from multiple angles is totally without value. In fact we know that even subtly different movements can elicit varying levels of fiber recruitment within a muscle in an overall sense (i.e. in terms of the percentage of total available fibers) due to differences in joint mechanics, and neural activation patterns, as well as varying involvement of synergistic and antagonistic muscle groups involved. So by all means experiment with different angles in your training, but don’t expect to be able to correct so-called “unbalanced” muscles this way, or to target specific areas of a particular muscle. Work to develop each of your muscles as completely as possible and shape will take care of itself. If you want to worry about “shaping” you should pay more attention to the balance between different muscle groups and work to bring up any weak groups you may have in relation to the rest of your physique.

Darkhorse · #2 04-15-2006, 04:13 PM

Quote:

The existence of the so-called "upper", "lower", "inner" and "outer" pectorals along with the assertion that it is possible to isolate one or more of these to the relative exclusion of the others in training, are among the most firmly entrenched myths

Muscle shape is a function of genetics and degree of overall development. As you develop a muscle towards its potential, it does change in appearance (generally for the better) but always within the parameters defined by its inherent shape.

Bravo!

EricT · #3 04-15-2006, 04:52 PM

Damn I wish all that wasn't true!

_Wolf_ · #4 04-15-2006, 06:39 PM

i actually believed each of these muscles were seperate for a LOONG time... i remember making workout plans (simple 4 day splits) which have to have one exercise targeting the "upper chest", then one for the "lower chest", etc.... so much time wasted..... *shakes his head*

Darkhorse · #5 04-17-2006, 03:03 AM

Quote:

Originally Posted by anuj247

i actually believed each of these muscles were seperate for a LOONG time... i remember making workout plans (simple 4 day splits) which have to have one exercise targeting the "upper chest", then one for the "lower chest", etc.... so much time wasted..... *shakes his head*

Everyone, and I mean everyone has been down that road before. :17: The only muscles anyone needs to seperate are legs and back [width vs. thickness]..Other than that, K.I.S.S. :240:

CROWLER · #6 04-17-2006, 11:02 AM

Thank you for the post. Now when I say that you can't target a certain area of the chest and someone says SHOW ME A STUDY PROVING IT111111 I now have my proof

CROWLER

Kane · #7 04-17-2006, 03:46 PM

Quote:

Originally Posted by CROWLER

Thank you for the post. Now when I say that you can't target a certain area of the chest and someone says SHOW ME A STUDY PROVING IT111111 I now have my proof

I just play stupid and when someone says something about upper and lower pec exercises....I ask them to flex their Upper and Lower Pec so I know what should be working when I do the exercise....Nobody can do it yet, guess I'll never know what part of my pec I'm working :( Oh well, ignorance is bliss I suppose muahahahaha.

EricT · #8 04-17-2006, 04:28 PM

Quote:

Originally Posted by Kane

guess I'll never know what part of my pec I'm working :(

The upper pec is the part close to the skin and the lower pec is the part close to the bone.

Ok, so I stole that.

CROWLER · #9 04-17-2006, 05:21 PM

Quote:

Originally Posted by Kane

I just play stupid and when someone says something about upper and lower pec exercises....I ask them to flex their Upper and Lower Pec so I know what should be working when I do the exercise....Nobody can do it yet, guess I'll never know what part of my pec I'm working :( Oh well, ignorance is bliss I suppose muahahahaha.

lol

I tried saying that but for some reason the girl slapped me

CROWLER