Is there an accurate way to assess the fast/slow-twitch muscle fiber ratio in your legs?
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?
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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
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)
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