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2008/05/20, 11:45 PM
Obviously genetics play a huge role in one's ratio of fast to slow twitch muscle fibres, but through hypertrophy, can this be changed?
For instance, if an athlete was to participate in a sport or activity that primarily used fast twitch fibres, and this stimulated hypertrophy, would the hypertrophy primarily occur in the fast twitch fibres, thus changing the atheltes muscle fibre ratio?
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2008/05/21, 08:49 AM
Yes.
To a degree.
Although hypertrophy occurs primarily in fast twitch fibers anyway, since slow twitch fibers don't have as much growth potential. That is one of the reasons you don't see hyuge cross country runners.
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SQUAT MORE ~Jesse Marunde
Blood Guts Sweat Chalk
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2008/05/21, 11:43 AM
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Quoting from Tinnuk:
Obviously genetics play a huge role in one's ratio of fast to slow twitch muscle fibres, but through hypertrophy, can this be changed?
For instance, if an athlete was to participate in a sport or activity that primarily used fast twitch fibres, and this stimulated hypertrophy, would the hypertrophy primarily occur in the fast twitch fibres, thus changing the atheltes muscle fibre ratio?
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You're on the right track.
Fiber type changes have been observed with training, but it has only been seen in one direction. With training and activation of high-threshold motor units, there is a transition from Type IIx to Type IIa. Transition from Type I to Type IIa (or x) remains highly doubtful.
Also, remember that hypertrophy is the increase in fiber size; increasing the number of muscle fibers (hyperplasia) has never been observed in humans.
So, the goal would be to increase the size of Type II fibers vs the Type I fibers.
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Michael
Strength & Conditioning is not everything; it just really sucks to be weak and slow.
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2008/05/21, 01:49 PM
Just building on the theory, but hyperplasia has been seen in human muscle tissue IN VITRO but not IN VIVO. What is interesting, is that it hasn't been made to occur due to stress (ie a training load) but rather under a stretch. A muscle can be placed under a stretch and forced to induce hyperplasia. However, since most flexibility limitations are due to constraints in the nervous system, rather than physiological restrictions, regular stretching won't cause this to occur either.
So while it may be possible, it's not something that is likely, and even if it was, you wouldn't have a way to train for it specifically. This is backed up by the fact that even upper level bodybuilders tend to fall in the same expected range of muscle fibers as untrained individuals.
They have been able (it's complicated) to produce a de novo formation of muscle fibers in rats using electrical stimulus.
Of course it could be happening in humans as well There are certain limitations that prevent us from studying this (for example, the fact that even a small muscle like the bicep can contain a quarter of a million fibers, and who wants to count that?
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SQUAT MORE ~Jesse Marunde
Blood Guts Sweat Chalk
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2008/05/22, 11:00 AM
Exactly.
MUSCLE BIOPSIES FOR EVERYONE!........lol :big_smile:
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Michael
Strength & Conditioning is not everything; it just really sucks to be weak and slow.
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2008/05/23, 09:48 PM
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Quoting from wrestler125
Although hypertrophy occurs primarily in fast twitch fibers anyway, since slow twitch fibers don't have as much growth potential. That is one of the reasons you don't see hyuge cross country runners.
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What's the deal with cyclists and soccer players then? My current kinesiology textbook shows a study that suggests trained individuals in those activities have a high ratio of slow twitch fibers, yet they seem to go through quite a bit of hypertrophy. I suppose that some activities are just better at inducing slow twitch hypertrophy?
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2008/05/23, 11:47 PM
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Quoting from rev8ball:
Exactly.
MUSCLE BIOPSIES FOR EVERYONE!........lol :big_smile:
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Maybe some things are better left unknown; I think it'd kill me if I found out that I was slow twitch dominant.
Though on the subject of muscle biopsies, are they even available to the general public? It seems that only those crazy Russians would go that far.
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2008/05/25, 02:03 PM
Your cause and effect is backwards. The best soccer players aren't slow twitch dominant because of their training, but they are the best soccer players because they are slow twitch dominant. 90 minutes is a long time, and generally the players that aren't built to withstand that don't continue playing soccer.
As for cyclists, yes they do hypertrophy (in the thighs) but not a lot. Compare a marathon cyclist to a sprint cyclist, and you'll see the difference. A sprint cyclist will have much more hypertrophy, while still doing much less work (think millions of repetitions vs thousands).
Just realize that I didn't say slow twitch fibers aren't capable of hypertrophy, only that they are much less prone to it.
And no, muscle biopsies aren't available to the general public. Most are done on cadavers anyways, it's tough to get someone to agree to do one on their own without medical reason.
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SQUAT MORE ~Jesse Marunde
Blood Guts Sweat Chalk
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2008/05/26, 11:27 PM
Very nice thread. And great info, Steve. It's been a while.
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I firmly believe that any man's finest hour, the greatest fulfillment of all that he holds dear, is the moment when he has worked his heart out in a good cause and lies exhausted on the field of battle-victorious.
--Vince Lombardi
"Decide what you want, decide what you are willing to exchange for it. Establish your priorities and go to work." H. L. Hunt
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