Re: Genetics and Muscle Growth - What are the factors?
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-Are there differnt mechanisms underlying muscular hypertrophy to different types of stimuli?
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great post. You are correct, it is very difficult to define the complete optimal exercise perscription.
One point you made that was fantastic was the use of local, isolation exercises in combination with compound to get growth, particularly for localized growth. In fact, the main way to answer your questions are really to test them in the lab on non responders. E.G. once you have identified a non responder, try and utilize more isolation exercises to bring out a greater localized response.
Now, as to your question of there being different mechanisms, there may be, but ultimately if you are going to get moderate or extreme muscular hypertrophy, no matter what the training stimulus is the end product is going to have to be activation of satellite cells and the subsequent addition of new nuclei to the cell. The evidence is clear on this.
Now as for techniques like blood occlusion, I think one possible mechanism this may work is through a different type of muscle damage, such as oxidative damage. Blood occlusion causes a lot of development of free radicals, and these cause damage to the muscle tissue, which would activate satellite cells. At least that is one possible mechanism.
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-Could it be that different people respond differently to different types of stimuli? Perhaps a non-responder to the definition of strenght training above would be a responder to other definitions of strength training?
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There is no question about it! Now that we have identified non responders, the next logical step is to examine if there are stimuli which would enhance their growth and bring out moderate to extreme hypertrophy (if this is possible) in them as well.
Here are my thoughts, and this includes you last question as well
1. Ultimately it comes down to activation of satellite cells
2. Satellite cell activation is a matter of transfering mechanical stimuli into a signal which activates satellite cells.
3. Key signals from training occur in the cell membrane of the muscle fiber. So, one possible intervention is to try and maintain the integrity of the cell membrane so that it can signal optimally. For example in the above study they trained 3 days a week hard. But, because the non responders were not releasing
as many local growth factors it may suggest that this type of training is too much stress for them, and instead they should train twice a week each muscle group. Or better yet, they should use a periodized training, alternating heavy load, eccentric concentric training, with less stressful days with less emphasis on eccentric training. By doing so, it allows a continual stimulus, but allows for more time for the cell membrane to maintain enough integrity so that it can signal optimally.
This is just one idea.
There are numerous ideas we need to examine in the lab, and I am definately going to think carefully about all of the things you suggest.
Well when we look at mechanical transduction, one of the main signaling molecules is nitric oxide. Mechanical stimuli activates nitric oxide synthase in the muscle cell to produce more N02 and this carries the signal to release local growth factors.
What we know is, in clincial conditions supplementation with Arginine ehances sattelite cell activation. It may be that non responders, may become moderate to extreme responders if we isolate them out in experiments and supplement them with arginine. I'd like to test this in the future.
Now, the most obvious supplement that can ehnance cellular integrity is HMB. In this case, if non responders were supplemented with a high dose of HMB, it may have maintained the integrity of their cell membrane, thereby enhancing mechanical signaling and brought them up to moderate to high hypertrophy.
So, overall I would say non responders may respond differently to both mechanical and nutritiional stimuli!