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Guys,

No disrespect to anyone here, but I′ve noticed a lot of people saying things like, "I′m primarily a fast-twitch person", or "You must have predominantly slow-twitch fibres in your body", etc., etc.

Personally, I think this is all a bunch of crap. Everyone has similar muscle fibre make-up in their body. Of course their are individual differences in terms of body structure and endurance, and so forth, but everyone′s muscle fibres behave in generally the same way and are laid out in generally the same way. To illustrate: The muscle fibre distribution in the leg muscles(designed for long duration and/or high-intensity work) is different from that of the arm muscles(designed for activities of brief duration), and both are different from the muscles of the neck(designed for support and frequent low-intensity movements). I don′t see how, for example, person A can have radically different muscle fibre make-up in their thighs than person B. Person A might have enormous thighs, and person B a set of toothpicks, but this has more to do with the size and number of muscle cells than how the various types of cells are distributed in proportion to one another.

Mother nature designed all our bodies to perform similar functions. Saying that one person has a significantly greater percentage of fast-twitch skeletal muscle fibres in their body makes no sense. Try applying the theory to cardiac muscle and you see how ridiculous it sounds. A healthy adult human′s resting heart will beat at 60-100 beats per minute, with the average being 72. You don′t see extremely low or high values except in cases of disease(e.g., heart failure, atrial fibrillation) or in elite athletes who perform a lot of cardiovascular work.

Please, correct me if I′m wrong.

CM

I′m no expert on this topic, but I tend to agree with you. I think there is some individual variation, But I find it hard to believe it′s as profound as some make it out to be.

From the medical info. in some of the studies, there are some differences, but not huge. Much of our typing is determined by our activity anyway. Weightlifting causes IIb fibers to start making IIa type heavy myosin chains, endurance people can slowly cause a shift to type I of the fiber types. They don′t ′change′ but ′act more like′ type I.
The one thing that bugs me is it doesnt matter how many type II′s or type I′s you have, a type II takes the same amount of time to fatigue no matter how many other type II′s there are. So what I′m saying, is I agree 🙂

Az

I remember when the Time Under Load (TUL) or Time Under Tension (TUT) was going to revolutionize our results by showing us the fiber type we have and the rep range we need.

Personally, I think 6-12 reps is optimal for everyone and I think the research shows it doesn′t even really matter. 🙂

Further,

It makes me wonder just how valid the Jones′ 80% one rep max test to determine fiber type/range really is anyway. I guess maybe it can be considered BS too. 😉