Every time I hear someone say an exercise targets fast or slow twitch fibers and have zero idea what they’re talking about, drives me crazy. While science is currently investigating I believe the last number I was told was 16 fiber types, the general teaching consensus is 3. Type 1, Type 2a, and type 2x. Fast and slow twitch in the science community btw is slowly starting to fade away because they realized thats not the best way of describing our muscle fibers. But for now, I put them into the blog explanation below:⠀
Your type 1 fibers are known as the slow twitch muscle fibers because they have the slowest firing rate, least amount of force production, and smallest circumference. They are however most resistant to fatigue and have the greatest aerobic efficiency of the other fibers.⠀
Your type 2a fibers are known as your fast twitch oxidative fibers because they have a fast firing rate, produce moderate force, and have a moderate circumference. As opposed to the type 1 fibers, your type 2 fibers fatigue rapidly because of the high force production and they aid in extended work at lower force output.⠀
Lastly, your type 2x fibers are known as the fast twitch glycolytic fibers and have the fastest firing rate of the 3 muscle fibers, the greatest force production, and largest circumference. They fatigue the fastest, but have the greatest creatine phosphate efficiency.⠀
Biagioli, Brian Dominick. Advanced Concepts of Personal Training. National Council on Strength and Fitness, 2012.⠀
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