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I've been running on and off for the past 12 years, having originally started in high school with XC. Given that fact, I've typically always been interested in running longer distances, however, within the past year or so, I've shifted my focus to sprinting.

From what I currently understand about the matter, sprinters prefer having a high ratio of fast-twitch muscle fibers. What I would like to know, or at least get some idea of, is what kind of fast/slow-twitch muscle fiber ratio my legs contain (without going to the hospital and requesting a biopsy, if that's even possible).

Upon searching YouTube, I wasn't really able to find any videos that demonstrate how to get an assessment of this ratio, other than this video, however, the guy is testing his chest, and, IMO, his test doesn't seem to be designed very well.

That being said, is there a way to at least somewhat accurately test the fast/slow-twitch muscle fiber ratio, specifically in your legs?

  • Muscle biopsies are possible. There is also some evidence that some fiber types can change as well. – JohnP Aug 29 '17 at 21:23
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    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3131401/ from 6ish years ago, but you'd need access to a good physiologist or research university willing to do it on and individual basis. – JohnP Aug 29 '17 at 21:26

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Accurately no. Unfortunately there are no proven ways to measure muscle fiber composition.

A muscle biopsy is an invasive technique involving the surgical removal of a small muscle tissue sample. This procedure is done to diagnose muscle tissue diseases when less invasive tests are not available. This is not a method used to determine whole muscle fiber composition.

Muscle Fiber Types

Skeletal muscle fibers can be classified into three types:

  • Type I: Slow oxidative fibers
  • Type IIa: Fast oxidative fibers
  • Type IIx: Fast glycolytic fibers

  • Most muscles contain mixture of fiber types, resulting in a range of contractile speed and fatigue resistance

  • All fibers in one motor unit are the same type

  • Genetics dictate individual’s percentage of each

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Training Effects on Muscle Fiber Type

Aerobic (Endurance) Exercise Such as jogging, swimming, biking leads to increased:

  • Muscle capillaries
  • Number of mitochondria
  • Myoglobin synthesis
  • Results in greater endurance, strength, and resistance to fatigue
  • May convert fast glycolytic fibers into fast oxidative fibers

Resistance Exercise (Anaerobic), Such as weight lifting or isometric exercises, leads to increased

  • Mitochondria
  • Myofilaments
  • Glycogen stores
  • Connective tissue
  • Muscle strength and Size (hypertrophy)
Mike-DHSc
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  • What is the source of this table/info? – Enivid Aug 31 '17 at 18:51
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    -1. Muscle biopsies can be used to determine composition, and have been used many times in clinical kinesiology. – JohnP Aug 31 '17 at 19:26
  • Also you have been warned about copy/paste without attribution (i.e. plagiarism) before. Please give the correct attribution. – JohnP Aug 31 '17 at 19:30
  • "Muscle biopsies can be used to determine composition, and have been used many times in clinical kinesiology." Where are your sources? How would you like me to cite a PowerPoint? – Mike-DHSc Aug 31 '17 at 23:11
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    If you have a source, even if it is a power point, I would expect you to cite where you got the power point. In this case, I found your entire answer in a SUNY biology course sample presentation. As far as sources, it's common knowledge in the kinesiology field. Here is a paper from 1972 describing using muscle biopsy to determine fiber types. http://www.exercisephysiology.net/articles/enzyme_activ_fiber_composition_untrained_trained_men_Saltin_1972.pdf . – JohnP Sep 01 '17 at 04:34
  • Here is a 12 year longitudinal study (abstract) where biopsies were used to determine changes in fiber composition due to aging, http://jap.physiology.org/content/88/4/1321.short – JohnP Sep 01 '17 at 04:35
  • Do you understand how a muscle biopsy works and when it is indicated?

    The study you cited is using a muscle biopsy for exactly what I stated. It is testing for sarcopenia an age related muscle wasting disease. You cannot determine an entire muscles fiber composition by using a tissue sample that's >.01% of your muscle.

    That is the equivalent of extracting a tiny tissue sample from your stomach and saying you can determine the % of fat vs lean muscle mass of your entire abdomen.

     – Mike-DHSc Sep 01 '17 at 05:17
  • Yes, I do. Your statement flatly says "No proven ways". Kinesiology has been doing it for years for various studies, in healthy, disease and aging populations. However, that aside, the rest of your answer is copy/paste from a secondary source without attribution. Please cite the relevant powerpoint and source it. If you cannot provide that, the answer may be deleted. – JohnP Sep 01 '17 at 14:49
  • "Genetics dictate individual’s percentage of each" - I believe research has suggested that long-term training can effect significant modification of muscle fiber type. –  Sep 25 '17 at 20:19
  • Also, aren't there some lactate tests that can give a rough idea of muscle fiber characteristics? –  Sep 25 '17 at 20:20
  • @joshreesjones Research is evolving on this. Was taught at one point IIa we're quite were only found in (small) specialized areas (your eye muscles for example). Think that's been well disproved at this point. From what I understand aerobic training IIx --> IIa. Type I (mainly the changes listed above). Anaerobic -- hypertrophy and resistance changes listed above. Could most certainly be wrong, just curious if you have an sources would love to know the current "accepted" theories if they have changed. Also same with regard to lactate would love to read over the research. – Mike-DHSc Sep 26 '17 at 03:35