Muscle Fiber Article

[Donald Lee]

This tells you most all you want or need to know about muscle fibers.

Edit: Crap can't upload it because it's too large. I'll upload it later on file sharing site and put up the link.

[Donald Lee]

http://www.megaupload.com/?d=PB0OYK9U

[Donald Lee]

Here are a couple easier to read articles:

http://home.hia.no/~stephens/fibtype.htm
http://home.hia.no/~stephens/fibtype2.htm

Gram for gram, the two types are not different in the amount of force they produce, only their rate of force production. So, having a lot of fast twitch fibers only makes a positive difference when the time available for force production is very limited (milliseconds), like the 100ms or so the foot is in contact with the ground during a sprint or long jump. It makes no difference to the powerlifter who may use 3-4 seconds to execute a slow, smooth lift.. In cycling, the only event that they are decidedly advantageous for is the match sprint, analogous to the track 100 meter dash, but with more anticipatory tactics and theatrics.

Does Fiber Type Change with Training?
This has been one of the 10,000 dollar questions in exercise physiology. It has been documented that elite endurance athletes possess a higher percentage of slow twitch fibers in the muscles they use in their sport, compared to untrained individuals. Is this due to genetic endowment or years of rigorous training? The answer is difficult to get at directly because we don't have comparative muscle biopsies of great athletes before and after they started training and excelling in their sport. However, good basic investigation using experimental models has helped generate some answers. The critical knowledge to remember is that fiber type is controlled by the motor nerve that innervates a fiber. Unless you change the nerve, you won't change fiber types from fast to slow or vice versa. Just this type of experiment has been performed in animals (generally rats). So, remember, there is no compelling evidence to show that human skeletal muscle switches fiber types from "fast" to "slow" due to training..

The first article I posted seems to state that there is some evidence that fiber types do change. These articles were posted in 1996, while the first article was from 2000.

[Brian Stone]

That's interesting. I only read your highlights so far. I seem to remember reading an article or sniplet recently on this subject that suggested there were fibers that were neither fast nor slow twitch but that had the potential to be either one based on training. I'm unsure of the validity of that, or how elastic their potential is after differentiation (assuming that this occurs at all).

[Donald Lee]

Originally Posted by Brian Stone

That's interesting. I only read your highlights so far. I seem to remember reading an article or sniplet recently on this subject that suggested there were fibers that were neither fast nor slow twitch but that had the potential to be either one based on training. I'm unsure of the validity of that, or how elastic their potential is after differentiation (assuming that this occurs at all).

You're probably referring to hybrid muscle fibers. The first article I posted seemed to indicate that the elderly tend to have more hybrid muscle fibers and not more slow fibers as we had once assumed. I wonder if any research in the past 8-9 years has validated or disproved this.

[Steven Low]

Yeah, we tend to have a "set" number of fibers. There's I think a small percentage of change maybe.. elderly probably.

Most of the slow/fast twitch has to do with the amount of hypertrophy in each due to specific sports training (power/strength vs endurance) and the subsequent other adaptations of the muscles to those stressors (increase glycogen, glycolytic enzymes, etc. vs. increase mitochondria, oxidative enzymes, etc.).

Also.. "Gram for gram, the two types are not different in the amount of force they produce, only their rate of force production." Most people don't know that but it's true. I think it has to do with some different isoforms of myosin being able to contract their heads faster in response to nerve impulses.

[Donald Lee]

Originally Posted by Steven Low

Yeah, we tend to have a "set" number of fibers. There's I think a small percentage of change maybe.. elderly probably.

Most of the slow/fast twitch has to do with the amount of hypertrophy in each due to specific sports training (power/strength vs endurance) and the subsequent other adaptations of the muscles to those stressors (increase glycogen, glycolytic enzymes, etc. vs. increase mitochondria, oxidative enzymes, etc.).

Also.. "Gram for gram, the two types are not different in the amount of force they produce, only their rate of force production." Most people don't know that but it's true. I think it has to do with some different isoforms of myosin being able to contract their heads faster in response to nerve impulses.

Steven, have you heard about Type IIX overshoot?

[Steven Low]

Originally Posted by Donald Lee

Steven, have you heard about Type IIX overshoot?

No... something like described in this (via google)?

http://www.ncbi.nlm.nih.gov/pubmed/1...,f1000m,isrctn


Also, is this described in the article above? I downloaded it but haven't read the whole thing yet.

[Donald Lee]

Originally Posted by Steven Low

No... something like described in this (via google)?

http://www.ncbi.nlm.nih.gov/pubmed/1...,f1000m,isrctn


Also, is this described in the article above? I downloaded it but haven't read the whole thing yet.

Yeah, that's it. It is described in the article I uploaded. I heard that the British track cycling team utilized the overshoot phenomenon in the Beijing Olympics and "blitzed everyone else, including the previously dominant Aussies" according to someone's account. I'm not sure about the veracity of this, but it's interesting nonetheless.

[Steven Low]

Originally Posted by Donald Lee

Yeah, that's it. It is described in the article I uploaded. I heard that the British track cycling team utilized the overshoot phenomenon in the Beijing Olympics and "blitzed everyone else, including the previously dominant Aussies" according to someone's account. I'm not sure about the veracity of this, but it's interesting nonetheless.

That's a pretty interesting phenonmena to be honest.

I'll read the article tonight or tomorrow, and then post my thoughts.