# Slow Twitch or Fast Twitch Muscle Fibers



## Richie1888 (Jun 7, 2007)

I was reading an article on this which made the basic suggestion that if your body is mainly fast twitch muscle fibers you should be training in a lower rep range ie. 4-6 and if your body is mainly slow twitch fibers you should be training in a higher rep range up to 15. 

If this is true how does the average person tell whether he is mainly slow or fast twitch ?


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## CowPimp (Jun 7, 2007)

I've read stuff like that, and even probably said it myself a long time ago.  However, from what I understand, fast twitch fibers are the only muscle fibers that have the potential for serious growth.

Also, the ratio of fast to slow twitch muscle fibers is muscle-dependent.


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## DOMS (Jun 7, 2007)

Aside from a biopsy, is there anyway to figure this out?


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## KelJu (Jun 7, 2007)

DOMS said:


> Aside from a biopsy, is there anyway to figure this out?



I doubt it. I have no proof, only observations, that I am mostly fast twitch. I have never been able to perform well in the higher rep ranges, but I always excelled in lower rep ranges. Everything I have ever done was training of fast twitch. 12 years of football trained for fast twitch. Football is 8 seconds of all out power pushing everything you got, then its 40 seconds of rest. The next play starts, 8 seconds of power than 40 seconds of rest. I have no endurance whatsoever. I suck donkey balls at cycling, but my legs are strong ass fuck at resistance training.


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## Richie1888 (Jun 7, 2007)

CowPimp said:


> I've read stuff like that, and even probably said it myself a long time ago.  However, from what I understand, fast twitch fibers are the only muscle fibers that have the potential for serious growth.
> 
> Also, the ratio of fast to slow twitch muscle fibers is muscle-dependent.



 i think im more confused now lol


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## KelJu (Jun 7, 2007)

CowPimp said:


> I've read stuff like that, and even probably said it myself a long time ago.  However, from what I understand, fast twitch fibers are the only muscle fibers that have the potential for serious growth.
> 
> Also, the ratio of fast to slow twitch muscle fibers is muscle-dependent.



Again, I have no science, only observations, but I believe that you can change a muscle from one type to another by how you train it. For example, a cyclist will have quads that are primarily slow switch, where as a football player would have quads that are mostly fast twitch. 


Now I don't want to assume the buggy before the horse here, so I will allow for the possibility that a cyclist has mainly slow twitch quads, before he started cycling and kept cycling because he was naturally good at it. Basically I'm saying that people can choose to do things they are naturally good at rather than becoming good at what they choose to do. 

I don't know which scenario is true. I'm simply entertaining the notion.


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## Gazhole (Jun 7, 2007)

I know in Russia they used to identify kids' primary muscle fiber type, and train them in sports appropriate to those to get yet another edge over everybody else in the long run, so there must be a way to find out.

I think i read that on IM somewhere...


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## CowPimp (Jun 7, 2007)

KelJu said:


> Again, I have no science, only observations, but I believe that you can change a muscle from one type to another by how you train it. For example, a cyclist will have quads that are primarily slow switch, where as a football player would have quads that are mostly fast twitch.
> 
> 
> Now I don't want to assume the buggy before the horse here, so I will allow for the possibility that a cyclist has mainly slow twitch quads, before he started cycling and kept cycling because he was naturally good at it. Basically I'm saying that people can choose to do things they are naturally good at rather than becoming good at what they choose to do.
> ...



Yeah, it's hard to see whether the person stuck to the sport because they were good at it, or they got good at it because of a shift in fiber type.  From what I understand, conversion between fiber types is only somewhat possible, and often you can't even shift the fiber type, but merely increase certain enzyme concentrations to kind of give one muscle fiber the characteristics of a different fiber type, to some degree (Rambling enough am I?).

Nonethless, the point is that you want to lift moderate to heavy weights to grow, lift heavy weights to get stronger, and lift light weights to improve endurance.  Don't worry about the details so much.


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## P-funk (Jun 7, 2007)

the muscles would still be a 'fast' twitch muscles, but it would start to assume 'slow' twitch characteristics depending on training parameters and motor qualities being worked on.

The cyclist example is a good one.  Their type IIa fibers exhibit more characteristics of type I fibers from all their endurance.


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## Dale Mabry (Jun 7, 2007)

Yeah, intermediate fibers are the only ones that seem to exhibit a change in characteristics, although it is said that one can train to non-sequentially recruit muscle fibers.


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## Witchblade (Jun 7, 2007)

CowPimp said:


> (Rambling enough am I?)


Not in the least. I think I got more FAQ material right here.


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## Phred (Jun 7, 2007)

I read on another board in a galaxy far far away that based on biopsies, the average human has fast twitch dominant quads, hams, lats, pecs, bis and tris.  And slow twitch dominant calfs and forearms.  Delts are about 50/50.  And the dominance is not a lot IIRC.  Something like a 47/53 ratio.  So it is not like your quads are 90% fast twitch fibers.  I have not scientific study to support it as I do not recall the site I pulled it from other than a BB site I stumbled across.

Based on the assuption that the ratio is farily close to 50/50, I can see how one can train a slow twitch dominant muscle to "act" like a fast twitch muscle over time.  It would be nice to know if there are any current and relevent studies to support or refute the assumptions.


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## fatmuscles (Jun 7, 2007)

the average human has fast twitch dominant quads, hams, lats, pecs, bis and tris. And slow twitch dominant calfs and forearms. 

this is right apart from the bis which are slow twitch, bis are mainly endurance muscles were as the tris are mainly strength muscles lol,


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