Fast and slow twitch muscle fibers.

The Difference Between Fast and Slow Twitch Muscle Fibers

In Build Muscle by Bobby MarandinoLeave a Comment

The types of muscle fibers.

If you were given a choice to run insanely fast for a short time or have the ability to run a very long distance at a moderate continuous pace which would you choose?

This is what makes fast and slow twitch muscle fibers different. Believe it or not, your type of muscle fibers determines your overall strengths and weaknesses when it comes to speed and endurance.

Depending on the ratio of your muscle being made up of fast and slow twitch muscle fibers, you will be predominately strong towards speed or endurance.

For most people, the main determining factor as to whether you’re strong in speed or endurance relies heavily on your genetics.

But what if you could somehow improve upon your choice of speed or endurance?

Well, you can!

Before you find out how, you first need to understand the difference between fast and slow twitch muscle fibers.

Type I Muscle Fibers

Type I muscle fibers are slow twitch muscle fibers. They take longer to warm up and use oxygen to fire. This combination of response and how they work allows them to go for a longer period of time without fatigue. Having an excess of Type I fibers will allow you to do well in things that test your endurance such as marathon running or long distance running.

Type IIa Muscle Fibers

Type IIa muscle fibers are one of two types of fast twitch muscle fibers. Type IIa muscle fibers are considered the “jack of all trades, master of none” of muscle fibers. While they are considered fast twitch muscle fibers, they technically are the in-the-middle or well-rounded muscle fibers. They are not the best at speed or endurance, but have a good balance of both.

Type IIb Muscle Fibers

Type IIb muscle fibers are the true fast twitch muscle fibers. They fire anaerobically and extremely quickly. This is due to them not needing oxygen to respond. However, the biggest flaw with them is that they fatigue the quickest out of all three types of muscle fibers.

Type IIb muscle fibers are great for sprinters who rely on short bursts of speed to win a race. While someone who has a lot of Type IIb muscle fibers will almost always lose a long distance run due to tiring out quicker, you can bet they will destroy everyone else at the beginning stages.These fibers are also extremely beneficial in weight training when you require a quick explosive burst of power.

Improving Your Choice of Muscle Fibers

While the ratio of fast and slow twitch muscle fibers is pretty much ingrained into your genetics, you can slightly alter your performance ratio in speed and endurance through training.

Most people have an even split of 50% Type I and 50% of Type 2 (both a and b) muscle fibers. Unfortunately you cannot expect to switch your body’s composition to 80% Type I and 20% Type 2 for example as defying your genetic composition is  not obtainable through training alone.

However, you can expect to slightly alter your composition through training and accelerating growth of specific types of muscle fibers quicker than others. Your best way of doing this is to focus your exercise on specific types of training.

When it comes to building lean muscle mass, in order to accelerate growth as fast as possible, you want to build on all three muscle fiber types. To do this, it is recommended that you do a balanced weight lifting workout. This means doing a combination of lower weight/higher reps and higher weight/lower reps in your sets. A great way to accomplish this is to do reverse pyramid sets. This is where you start off with heavy weight/lower reps and as you progress through your sets you do less weight/more reps.

Which do you prefer: endurance, speed, or a balance of both? Why?

About the Author

Bobby Marandino

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The founder of Limitlessly Fit, Bobby started Limitlessly Fit to share his lifelong passion of fitness to help guys build lean and ripped physiques. Bobby is well educated in many fields, holding a Bachelors degree, two Masters degrees, and several certifications. He also has over 10 years of experience and university-based education in fitness and nutrition.

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