T Nation

Genetics and Muscle Types

Just curious if anyone happened to catch the cover article of “Scientific American”. Very interesting stuff- a lot about the different types of muscle fibers, ways that they can potentially change and some interesting thoughts on genetics- future potential therapies, etc.

Yes dude, that was a great reading… only problem is… i think that perhaps strength training turns IIx into IIa and that it would be helpful to know which fibers help glide/guide movement and which fibers are better for control and are x fibers stronger or just faster… which ones are stronger? anyways thats just a few questions i have about that.

I glanced at the article, and although it is cool to see the molecular biology of muscle getting mainstream science coverage like that, I was a little disappointed. First off, I think there were several editorial mistakes. If I recall, they mixed up the fiber designation a couple of times, which can be pretty confusing to uninitiated who might be taking what the authors say as gospel. Also, if I recall correctly, they emphatically stated that muscle cells cannot multiply. That is certainly debatable. Finally, although I think that gene therapy for human performance will be a reality in a few years, they went a bit overboard with the scenario. It was entertaining, but a bit overdone. If anyone would like to see more of these “sci-fi” type articles about the future of muscle science, speak up. TC and I were talking about doing one of these just the other day and didn’t think there would be much interest.

Yeah Steve, I would have to agree with you. I found myself confused about the mix ups on naming muscle fiber types but figured out what they must of meant. I very much agree that it was over done, but fun. What I actually found to be the most interesting was what they had to say about changing muscle types. I don’t know much of anything about it, but I thought that muscle fiber types couldn’t change, only that certain types of training would effect certain types of fibers. Although they state that marathon runners and sprinters are born with differing muscle fiber makeup, they seem to suggest that they could , by training differently actually alter their muscle type percentages. Something to do with the nerves firing certain muscle types and after time actually changing the muscle type to another type. Did I understand this correctly? If so, is this really plausible? As far as the sci-fi article, if you and TC don’t find it to be interesting, then there wouldn’t be much point, but if you guys print it I will be sure to read it. There hasn’t been anything in T-mag to make me yawn yet.

I would be interested in such an issue. Make sure you include at the end of the issue an article on how the FDA and/or DEA will prevent all of these amazing advances from ever being used by healthy adults.

If you ever decide to do an ‘Abolish the FDA’ article (or better yet, a full issue devoted to the topic), I know a few people who would be interested in writing it.

You’ll have to forgive me because I loaned my copy to someone else, so I am working from memory. I believe they were using the cross-innervation experiments to support the argument that fiber type is dependent upon innervation. In these experiments muscle fibers (type IIb) were transplanted and innervated with nerves from type I muscles and a type conversion occured in the type IIb fibers. Now this isn’t exactly physiological so it doesn’t necessarily mean that by changing firing patterns you can totally convert a muscle, but it does support the idea that neurological training can affect fiber type characteristics. The problem is, with limitations inherent in working with humans, no one knows the answer to this question definitively, but it’s an interesting debate. Most practically oriented muscle physiologists will agree that fiber type conversion will occur to a certain extent with training, but it is a much slower and less distinctive process than doing a cross-innervation. Gene therapy would be the shortest of short-cuts (if it can be made practical), but there is a long way to go.

Maybe I will revisit the issue of an article with TC.