MHC-IIX and MHC-IIA isoforms and muscle hypertrophy after long layoffs: Interesting.

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    MHC-IIX and MHC-IIA isoforms and muscle hypertrophy after long layoffs: Interesting.


    "A recent study looking at fiber type conversions during muscle hypertrophy may have uncovered a possible mechanism for this phenomenon. For those of you not crazy about scientific lingo bear with me. Towards the end you will see what Iím getting at with this study. In this study the distribution of myosin heavy chain (MHC) isoforms, fiber type composition, and fiber size of the vastus lateralis muscle were analyzed in a group of adult sedentary men before and after 3 months of resistance training and then again, after 3 months of detraining. Following the period of resistance training, MHC IIX content decreased from just over 9% to 2.0%, with a corresponding increase in MHC IIA (42% to 49%). Following detraining the amount of MHC IIX reached values that were higher than before and during resistance training, over 17%! As expected, significant hypertrophy was observed for the type II fibers after resistance training, and even remained larger than baseline after 3 months of detraining.

    Myosin heavy chain isoforms, or MHCs, refer to the types of contractile protein you see in a given muscle fiber. MHCs determine how the muscle fiber functions. MHCs are what make a fiber "fast twitch", "slow twitch", or something in-between. Certain MHCs are known to undergo a change in response to resistance exercise. In this case, fibers that contain MHC IIX are fibers that arenít really sure what kind of fiber they are until they are called to action. Once recruited, they become MHC IIAs. So, fibers containg MHC IIX proteins serve as a reservoir of sorts for muscle hypertrophy because the can transform themselves into fibers containing MHC IIX which grow easily in response to training.

    Like any great study, these researchers found what they expected as well as a little extra that they didnít. I think this study caught my attention because it showed a long-term alteration in skeletal muscle following resistance training. It has been this long-term change that has been the focus of my own training philosophy, which incorporates what I call "strategic deconditioning". This study showed that resistance training decreases the amount of MHC IIX while reciprocally increasing MHC IIA content. This was expected and has previously observed with changes in fiber type after resistance training. What they didnít expect was that detraining following heavy-load resistance training seems to cause what they refer to as an "overshoot" or doubling in the percentage of MHC IIX isoforms, significantly higher than that measured at baseline. What does this mean? It could mean that there are more fibers available for hypertrophy (growth) after a lay off from training than there are before you start training. This could very well explain the "muscle memory" effect many of us have experienced ourselves. It may also have implications for natural bodybuilders looking to overcome long-standing plateaus.

    There are a few questions that this study did not answer. For instance, they waited until 3 months after they stopped training before they took final measurements. It would have been nice if they had taken measurements regularly so that the optimal period of detraining could be identified corresponding to peak MHC IIX levels. Because it takes 3-4 weeks for these contractile muscle proteins to turn over, it would take longer than one month and probably less time than 6 months (previous research). Still the optimal time remains to be elucidated.

    Also, how would these guys respond to the same training regimen after the detraining period? Would their quads grow to their previous trained size, or even further? How long would it take? These questions, if answered, may add a new twist to typical training regimens. It may very well be that extended breaks from training may actually allow greater growth over a 12-month period than if training is uninterrupted. For serious athletes and bodybuilders, this would be important information and could significantly extend their competitive careers."

    Now bear with me guys. I found this study while scouring through MGF/IGF studies that I have been researching like MAD lately since I just created (with the help of xtraflossy) an MGF-IGF guide to everything basically and this came as a great surprised to me.

    Basically what this is saying is this. MHC-IIX fibers don't know what they are. They are not really fast or slow twitch fibers. You can recruit these, however, to become fast twitch (growth) fibers by training them. If you notice the concentration of MHC-IIX fibers dropped exactly 7% from when an untrained person became trained and inversely MHC-IIA fibers incrased exactly 7% showing that these X fibers changed the the hypertrophy inducing A fibers. When these people were DETRAINED however, meaning they stopped training for a long period of time, the MHC-IIX fibers (who were originally at 9% and dropped to 2%) went from 2% up to 19%!!! Now what does this mean? This means that if you train and then detrain your muscles you can increase the amount of fibersr that are available for hypertrophy, possibly. Since this experiment didn't train these people again after this layoff it is unclear whether your MHC-IIX fibers would drop only 7% again (down to 12%) or if you could push past this and convert even more MHC-IIX fibers to MHC-IIA fibers, inducing more hypertrophy.

    This could be the reason why people who get injured have GREAT success building muscle after long layoffs. I just posted this as something to think about. I will research it more and try to get more from it as time goes on and will post it here whenever I find it.

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    Thumbs up Re: MHC-IIX and MHC-IIA isoforms and muscle hypertrophy after long layoffs: Interesti


    This is very interesting to me LakeMountD - As this summer i wont be able to train much b/c ill be working 80 hrs selling books who knows where (wherever im assigned) I know im gonna lose some if not a lot of mass and would like to do it in the most "beneficial" way possible if that makes sense - so i can make an astounding comeback when the job is done. Thanks for doin the research on this.

    -Soma
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    Re: MHC-IIX and MHC-IIA isoforms and muscle hypertrophy after long layoffs: Interesti


    Quote Originally Posted by soma
    This is very interesting to me LakeMountD - As this summer i wont be able to train much b/c ill be working 80 hrs selling books who knows where (wherever im assigned) I know im gonna lose some if not a lot of mass and would like to do it in the most "beneficial" way possible if that makes sense - so i can make an astounding comeback when the job is done. Thanks for doin the research on this.

    -Soma
    Yea I would try to keep the heavy cardio to a minimum as I believe cardio has a profound effect on this study. I don't think the people in this study did very much cardio in between so there wasn't much type 2 to type 1 conversion. You can still do things to burn fat, like 65% max hr training, just dont start getting up in the heavy 85% area, etc. Let me know how it works out though and when you get back into it, hit me up I will help you with training and diet .
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    Re: MHC-IIX and MHC-IIA isoforms and muscle hypertrophy after long layoffs: Interesti


    Quote Originally Posted by LakeMountD
    Yea I would try to keep the heavy cardio to a minimum as I believe cardio has a profound effect on this study. I don't think the people in this study did very much cardio in between so there wasn't much type 2 to type 1 conversion. You can still do things to burn fat, like 65% max hr training, just dont start getting up in the heavy 85% area, etc. Let me know how it works out though and when you get back into it, hit me up I will help you with training and diet .
    Well it's not all that recent it's from 2000, but honestly it's one of my favorite studies on detraining but please understand that these subjects detrained for 90 days and the myosin shift they saw did not even begin to occur for 30 days. In other work that used the exact same protocol (loading and unloading) by Kadi, looked at training and detraining's impact on satellite cells saw that the changes in satellite cells mimicked the Anderson study (the one you quote from above). So just wanted to say that these changes are not happening all that fast and to see these same type of results the detraining period would need to be around 30 days, that's a pretty long time.

    Secondly there is very very little evidence that the myosin shift to type one actually occurs. One must understand that the fiber makeup of your muscle is largely predetermined at birth. Yes there are slower shifts occuring but these are generally within the same MU type, IE Fast Fatiguable to Fast Fatigue Resistant but they are still Fast Type Units. Recent studies are showing that this may even be true in type I fibers as well, a really slow fatigue resistant and an intermediate type 1 as well. But this is still being researched.

    Dan
    www.hypertrophy-research.com
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    Re: MHC-IIX and MHC-IIA isoforms and muscle hypertrophy after long layoffs: Interesti


    Quote Originally Posted by Dan Moore
    Well it's not all that recent it's from 2000, but honestly it's one of my favorite studies on detraining but please understand that these subjects detrained for 90 days and the myosin shift they saw did not even begin to occur for 30 days. In other work that used the exact same protocol (loading and unloading) by Kadi, looked at training and detraining's impact on satellite cells saw that the changes in satellite cells mimicked the Anderson study (the one you quote from above). So just wanted to say that these changes are not happening all that fast and to see these same type of results the detraining period would need to be around 30 days, that's a pretty long time.

    Secondly there is very very little evidence that the myosin shift to type one actually occurs. One must understand that the fiber makeup of your muscle is largely predetermined at birth. Yes there are slower shifts occuring but these are generally within the same MU type, IE Fast Fatiguable to Fast Fatigue Resistant but they are still Fast Type Units. Recent studies are showing that this may even be true in type I fibers as well, a really slow fatigue resistant and an intermediate type 1 as well. But this is still being researched.

    Dan
    www.hypertrophy-research.com
    Absolutely correct, I didn't post the entire study, just the abstract portion since no one would have actually read the entire study haha. But that is definitely what he said, the study time points were at 30 and some other points all the way to 90. It would have been a much better study if they did it at 15, 30, 60, 90 and then retrained these people and see if they saw a marked increase in hypertrophy than when they were originally trained. Oh well leaves some to the imagination .
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    Re: MHC-IIX and MHC-IIA isoforms and muscle hypertrophy after long layoffs: Interesti


    Quote Originally Posted by LakeMountD
    It would have been a much better study if they did it at 15, 30, 60, 90 and then retrained these people and see if they saw a marked increase in hypertrophy than when they were originally trained. Oh well leaves some to the imagination .
    Not sure if detraining for less time would make any difference. MHC takes around 20-30 days to turnover anyway, the heavy chain are the slowest of the fractions in turnover. So at 15 days the most they would have seen is shifting in the sarcoplasmic (faster turnover fraction) which they weren't even looking at.

    As far as retraining, a lot would also depend on the time of the detraining period. If too long then the neural eficiency increases from the training period would be lost and therfore hypertrophy would be diminished in the first 3-4 weeks anyway. If too short you still have the decreased "anabolic potential" existing so it would be slower to hypertrophy the tissue.

    As obviously you enjoy studies, then you probably already know that the more varaiables you throw into the mix the harder it is to come out of the study with anything really representative. Too many variables = too many possible outcomes. Just to hard to manage the controls.

    I have written a very nice article on variables and how they influence the significance of a study, if you would like a copy of it or of the Kadi study I mentioned let me know and I'll shot them to you.

    Dan
    www.hypertrophy-research.com
    Dan_Moore@hypertrophy-research.com
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    You wont lose all your muscle if you keep your diet in check. Breaks are awsome for breaking training plataus, even if you just take a 2 or 3 week break it is great to let your body heal all the way. I have a hard time taking time off from the gym and an even harder time staying on a diet while I am not training.
  

  
 

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