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Catching the Morning Train, Fast-Twitch style!

Catching the Morning Train, and Fast-twitch Muscle Fibers

Have you ever been just a little behind the clock and needed that 100 yard sprint from your car to the train? Maybe you had to sprint to catch the subway train that will get you to the meeting on time? Whatever the case may be, during these moments of panic, you are recruiting fast-twitch muscle fibers to get you on that train. 

First of all, Chris, what the heck are fast-twitch muscle fibers, and why do I care to train these fiber types? Well, there are different types of muscle fibers in the body, and they are classified according to how they churn out energy. Also, these different muscle fibers can be trained via specific exercises, depending on how they produce energy and type of force generated. There are many types of muscle fibers that have been identified, but typically these fibers are classified as either slow-twitch or fast-twitch.


Today we will give attention to our fast-twitch muscle fibers, and a later blog will touch on the slow-twitch fibers. For now, just understand slow-twitch fibers are Type I and fast-twitch fibers are Type II.

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

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 (Adenosine triphosphate, currency to create 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.

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 threshold. 

  • Large fast-twitch fibers reach peak force quicker and can generate higher amounts of force than slow-twitch fibers.

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

The number of fast-twitch muscle fibers can be increased through strength and power training.

Fast-twitch fibers are responsible for the muscle size and definition. Don't believe me, check out the image below...

                                                         Sprinter                             Marathon Runner

So, what does all this have to do with your sprint to the train?

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 be sure your sprint to the train doesn’t end with you sitting on the bench waiting for the next train to arrive?

  • 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 ATP supplies to renew; 60-90 seconds should be enough time.

Understanding the 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 catch that early train you cannot afford to miss. 

Contact PT by CV today to begin your journey to a healthier life! Mention this blog and get one free session!

This article was provided by PT by CV
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