Muscle Fibers Face Off: Slow Twitch vs. Fast Twitch

by | Updated: December 3rd, 2016 | Read time: 2 minutes

Q: What’s the difference between slow twitch and fast twitch muscle fibers?

Amy Marsh answers

A: Knowing the difference between slow twitch and fast twitch muscle fibers can help determine the type of sport you will excel in. Read on for my break-down of muscle fibers (you won’t need a recovery day after this).

Whether you’re a sprinter or a marathoner, those muscles deserve quality recovery fuel.

Most people are split 50/50 – but not in a bad way. Your body is likely composed of 50% slow twitch muscle fibers and 50% fast twitch. However, some of you could be genetically blessed with a higher percentage of one or the other (like those marathon record holders who I swear are half cheetah!). I say blessed, because both types of fibers serve a unique purpose when it comes to physical activity. And though slow twitch and fast twitch fibers do not hold the same “powers,” they are generally equal in strength.

Slow Twitch:

Slow twitch muscle fibers are efficient in using oxygen to create energy for continuous muscle use. They fire more slowly than fast twitch fibers and can withstand long periods of activity before fatigue sets in. Therefore, slow twitch muscle fibers are more useful for endurance events, such as long-distance running and cycling (think marathons and century rides).

Fast Twitch:

These muscle fibers are the opposite and do not burn oxygen to create energy. Fast twitch fibers tire out much more quickly than slow twitch fibers. That’s why they are useful (and quite active) during sprinting, jumping and other explosive body movements.

So which muscle fibers do you think you have the most of? Let us know in the comments below.

This table is a glance at how the muscle fibers face off. Feel free to pin, save and share it – you may help someone else find their athletic potential! And remember that no matter which muscles you engage more, they need the right mix of amino acids, carbs and protein for optimal recovery.


Amy Marsh is a four-time Ironman champion, two-time IronDistance champion, and was named the 2010 USAT Long Distance Triathlete of the Year. Brandon Marsh has been competing in triathlons since 1988, and can be counted on to be a top-10 contender in every event he enters. Got a question about swim-bike-run or sports nutrition for Team Marsh? Email them at “˜Like’ them on  Facebook  or follow on Twitter: Brandon @BrandonMarshTX and Amy @AmyCMarsh.