Neuromuscular physiology is not my strong suit, but this is interesting because I feel their must be some relationship between muscle length during a contraction, and where the most tension is placed within the muscle. In other words, does muscle tension remain evenly spread throughout the entire pec major (or one of the heads) during a complete muscle contraction... or does it transfer inward from the origin/insertion towards the middle as the muscle shortens?
I would instinctively say that the latter is true, but I haven't studied the neuromuscular aspects of weight-training yet so I'm truly not sure.
The origin of the the sternal head of the pec major is quite expansive, however. It includes the sternum, the first 7 or 8 costal cartiliges, and even a little bit onto the apneurosis (connective tissue) of the external obliques. That said, the origin of the pec depending on the fiber may be the sternum (ie. inner) or further onto the costal cartilige (outter). Displacement of where the fibers originate and rib cage structure are just one of the genetic make ups that account for various shapes of developed pecs between individuals.
During contraction, however, the entire fiber shortens. One nerve innervates a number of muscle fibers...not several nerves innervating different areas of each fiber.
I guess I'm referring more to muscle damage than actual motor recruitment. I agree you cannot target the recruitment of motor neurons in different parts of a single muscle. What i'm not sure about is whether or not different angles, exercises, contraction length etc... create more stress tension on various parts of a single muscle (i.e. the inner/outer portion of the pec major). And if so, would this lead to more muscle damage and hypertrophy of a particular portion of the pec or not.
I'd imagine that the length of the lever (arm position relative to resistance) would give you a sensation of more inner/outer chest. If the lever is long, more torque is required to move the limb. I occasionally do burn-out cable flies and notice the inner portion of my chest where the pec attaches to the sternum feels tender. I have long dismissed "isolation" of the inner fibers of the muscle because I think in terms of biomechanics...a pec fly is an exercise withe a long lever that puts the pec through its entire range of motion with high resistance, and thus the muscle is literally pulling more on where it meets the bone. This tender feeling I have could be micro-fractures from tendon/bone attachment sites or small tears in the tendon.
I have no researched studies to prove this...but I am just picking my own brain trying to make sense of where some of you are coming from.
I've given up on trying to help people out to understand. If you're not telling the what they want to hear, or if its challenging everything they've read in their lifting career (which, unfortunately is quite limited to muscle and fitness, generally), then anything you say goes in one ear and out the other. Its a waste of my own energyOriginally Posted by jmdunni;2909642[B
“Lord, whom shall we go away to? You have sayings of everlasting life"- John 6:68
WHAT has science offered?
Grab the bar at a width that feels comfortable/natural (20" grip" works for me) and focus on increasing your bench. Your chest will respond accordingly. Remembering to always emphasize discouraging muscle imbalances with a balanced training program. That is, if you're benching, you should be rowing as well.
For the record (and to minimize perpetuation of any more irritating myths), the only true exercise that 'destroys' any articulation (joint) in the body or brings forth any sort of injury is the exercise that is executed with poor form & lacks proper technique. Push-ups with added resistance are no healthier for your shoulders than the bench press performed with flared elbows, etc.
I also have really long arms, I'm 6'2 and burdened with long limbs. The wider grip seems to help a bit, or getting help to take it off the rack to get started when going heavy.
I know that the majority of fiber damage and microtears occurs during eccentric (negative) contraction. The greatest amount of contraction force happens when the muscle is approximately halfway lengthened/shortened. This is passive length tension relationship. Therefore I would think that the greatest amount of muscle fiber damage would occur during an eccentric movement with the most amount of weight possible, when the pec major is at that halfway point. And Im pretty sure the actin and myosin filaments that the muscle fibers consist of are ALL lengthened/shortened to the same degree during a movement.
The only variable I can think of is angle. The sternal fibers (inner chest) run in a horizontal fashion. This arrangement is most emphasized upon during "D-2 PNF pattern". Basically thats when the arm is reached dpwn across the body towards the opposite leg. Exercises that would incorporate this movement are decline bench, dips, cable crossovers- in this particular pattern of course. Incline and flat presses will emphasize moreso on the "top-middle" and top of the chest.
Now dont confuse what Im saying for "isolating" a certain portion of the chest. Impossible, because as stated before, its one muscle and is innervated by the same nerve root.
Nonetheless, movin weight, I honor your curiosity and I agree that there should be a study done.
Suffer now.. and live like a champion later.
I can target them for DOMS...but I can't make one part grow more than the others. No matter what I target they grow together so it's a waste of time to isolate pecs imo.
Incline makes upper hurt, doing super wide flies makes the outer hurt, crossovers hurts the inner, grip width affects it on flat, etc. But I don't notice one part of my pec lagging really.