Slow Twitch vs. Fast Twitch Muscle Fibers

Slow Twitch vs. Fast Twitch Muscle Fibers understanding how your muscles work can improve your training routine so that you find optimal success. If you are going to do the work, you should do the work that will be the most beneficial to your success.

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For week eight of my 52 Tips for Health and Fitness Success where each week I write a post sharing health or fitness tip or tips that I find useful in my daily life; today I want to introduce you to your slow and fast twitch muscles and why you should care how you train them.

Did you even know that you have two different types of muscle fibers?

The average person has about 50% slow and 50% fast fibers in most of their muscles.  However people are either fast twitch fiber dominant, slow twitch fiber dominant, or a mix of both and can be as much as 80% slow or fast twitch muscle types.

Why should you care?  Because understanding how your muscles work can improve your training routine so that you find optimal success.   If you are going to do the work, you should do the work that will be the most beneficial to your success.

Right?  Right! Well to get the success you want, you must understand how your muscles work.  Otherwise your exercising impaired.

So here is the science behind why your muscles do what they do.

The composition of slow-twitch to fast-twitch muscles in your body is largely based on genetics.  Each of us is born with more of a certain type of muscle fibers, slow or fast.   We can’t really change the percentage we have, but we can train what we have to the best ability for the optimal results.

Slow Twitch muscle fibers (Type 1) are responsible for long duration, low intensity activities walking, jogging, etc.

Fast Twitch muscle fibers are broken into two groups.  Fast (Type 2)  and Faster (Type 3).

  • The first group of fast twitch muscles fibers (type 2) are for fast low intensity movements, they have a fast recovery and are resistant to fatigue.  These muscle fibers are great for strength training exercises.
  • The second groups of fast twitch muscle fibers (type 3) are the faster muscle fibers responsible for short duration high intensity activity, explosive short activities like sprinting, and jumping.  They focus quick movements and contract 10 times faster than your slow twitch muscles.

Why do these fibers act differently?

It has to do with oxygen.  If you read my post about Aerobic vs. Anaerobic, I explained Aerobic means “with oxygen” and Anaerobic means “without oxygen.”

Slow Twitch Muscle Fibers rely on a rich supply of oxygenated blood that they use to produce energy for your muscle contraction.  Aerobic exercise; jogging biking, walking, etc.

Fast twitch muscle Fibers (type2) produce their energy from oxygenated blood and their lactic acid.  Mix of Aerobic and Anaerobic; mostly lifting weights, pulling, etc.

Fast twitch muscle fibers (Type 3), hardly use any oxygenated blood and therefore fatigue quickly. Anaerobic; sprinting, jumping, kicking, etc.

This may be part of the reason some people can last longer in that high intensity exercise class or why they are predisposed to building muscle.

Now you know the science behind how your bodies muscle fibers are working, you need to make sure you are mixing up high and low intensity workouts that will work both the slow and fast twitch fibers.  Even if your body composition is made up of mostly slow twitch muscle fibers that doesn’t mean you can’t get faster and stronger working your fast twitch muscle fibers.   Which are SO important as we get older.  Think about when you go to slip and fall, all the muscles that fire to catch you from falling are fast twitch.

Fast twitch exercises also burn more energy (calories and fat) in less time than slow twitch exercise, which can lead to gain in muscle mass, which lowers blood pressure and improves strength and balance.

In recent years, sports science has proven that women who focus on stimulating their fast-twitch fibers by doing weight training, sprints and kickboxing lose fat and overall body weight far quicker.

Plyometrics a form of exercise that involves rapid stretching and contracting of the muscles, designed to increase strength is the perfect type of exercise to strengthen those fast twitch fibers.

 Training Fast Twitch Muscle Fibers with Plyometric Exercises


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