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Old 12-18-18, 05:56 PM
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Muscle biopsies. But this is also somewhat invasive, as you basically take a "core sample" of the desired muscle. Key words there are desired muscle. This will only tell you the make-up of the muscle that is sampled, so it's not a super complete picture of what's going on with an athlete, unless one decides to sample all of their muscles! I had this done on my quads when I was racing as I had an opportunity to be a guinea pig in a university study. It hurts, A LOT! I recommend the standing long jump test instead.

The thing you need to remember is that all of the bodies skeletal muscles are comprised of a mix of 3 different kinds of fibers (there is some literature that divides them even further, into 5 types, adding switchable 2a and 2b fibers). These are Type 1 (red slow/slow oxidative), Type 2a (red fast/fast oxidative), and Type 2b (white fast/glycolytic). Postural muscles trend to being highly red slow for just about everyone (with little variance as to the fiber proportions throughout the population at large) , and prime movers is where you see wide variations in fiber type proportions, not just from person to person, but also within a single body. Upper extremities tend more towards 2b (white), and lower extremities tend to be more varied (even within sprinters).

Type 2a fibers, in some instances are adaptable (this is where "other literature" comes in, as well as Type 2b reverting to 2a) , unlike Type 1 and Type 2b. With the right loads, Type 2a can become 2b, but this isn't always the case.

Soooooooo... there is a "hard ceiling" to everyone's genetics, but unless you are decidedly slow twitch, there is a "soft ceiling" that one runs into as a sprinter before muscle fiber types will start adapting.

Last edited by taras0000; 12-18-18 at 05:59 PM.
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