Fitness, Science

The Need-To-Know On Fast-Twitch Fibers

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Have you ever ran, literally sprinted a few hundred yards?

It’s possible some of you include sprinting in your routine (if you don’t, read why you should here). Maybe you had to sprint to catch the bus to get you to school on time when you were younger, or were in a sport that required explosive movements? Whatever the case may be, movement requires muscles to move bones and you have different types of muscle fibers. However, we simplify these various muscle fiber types by categorizing most as either fast-twitch or slow-twitch. When sprinting or performing explosive movements you are recruiting mostly fast-twitch muscle fibers to accomplish that action. 

What Are Fast-Twitch Muscle Fibers?

We have a few types of muscle fibers and they are more strictly classified by how they “churn out energy.”  Each unique muscle fiber type can be trained using specific exercises, depending on how they produce energy and the type of force generated by the exercise. To learn more about the many types of muscle fibers in a fairly humerously-scientificly fantastic manner, visit here. To learn a bit more about how muscle contractions work, try this link

Today we will give attention to our fast-twitch muscle fibers, and a I’ll write tomorrow on the slow-twitch fibers. For now, just understand slow-twitch muscle fibers are Type I and fast-twitch muscle fibers are Type II.

Here’s the scoop on Fast-twitch (Type II) muscle fibers:

1. Fast-twitch fibers are additionally classified into; 

  • fast-twitch IIa – fast oxidative glycolytic, because they use good ole oxygen to help convert glycogen to ATP (currency for energy)
  • fast-twitch type IIb – fast glycolytic, which rely on ATP stored in the muscle cell to generate energy.
  • Fast-twitch fibers are considered “white fibers” because they have a lighter appearance than slow-twitch fibers due to less blood flow.

2. Fast-twitch fibers will be enlisted or activated only when the force needed is greater than the slow-twitch fibers can meet.

  • This is why fast-twitch muscle fibers are considered to have a high aerobic threshold.
  • Large fast-twitch fibers reach peak force faster and can generate greater amounts of force than slow-twitch fibers.

3. Fast-twitch fibers can generate substantial force, but are quicker to fatigue than slow-twitch fibers.

4. Fast-twitch muscle fiber density can be increased through strength and power training.

5. Fast-twitch fibers are responsible for the muscle size and definition. 

So, what does all this have to do with your ability, want or need to sprint? Simple. Fast-twitch fibers are recruited for explosive, strength-and power-based movements, i.e. sprinting. Ok, so how do you engage the fast-twitch fibers during exercise so that you can ensure growth and development of these muscle fiber types?

  • Train with heavier weight. Now, I’m not saying you need to load 400lbs on the bench press, but heavier weight will recruit more fast-twitch muscle fibers.
  • Explosive, and power movements, will recruit more fast-twitch fibers.

***Keep in mind fast-twitch fibers fatigue quickly, so heavy weight or explosive movements should be limited to two to six repetitions for maximum effectiveness.***

Also, fast-twitch muscles deplete energy like crazy, and very quickly, so allow longer rest periods between exercises to allow  adenosine tri-phosphate (ATP) supplies to renew; 60-90 seconds should be enough time., if not, wait a little longer. 

Understanding the different muscle fiber types, how they allow you to function in everyday life, and incorporating exercises to improve their performance will not only improve your quality of life, it will help you the next time you need to sprint after your kid. 

I want to share ways you can get in-depth training, advice, and begin making your health a priority. 

Again, I want to sincerely thank you for taking the time to read my post. Don’t forget to tell friends and family about me! Share if you’d like and comment below to get a conversation started.  I wish you the best, and I hope to hear from you soon!

Coach Slice

chris@coachslice.com

Coachslice.com

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