Muscle Fiber Types and How They Affect Your Workouts

Last Updated on June 2, 2020

Building a body depends on several factors, which include exercise and a particular diet. However, if you are one of those who are religiously working out and not cheating on your diet, but still your muscle growth is not satisfying enough, do not worry; it is normal. For those who do not know, your slow progression might be due to the types of muscle fibers. Every individual’s muscle fiber types also decide how quickly or slowly, he or she will be able to get bigger and stronger.

Muscle Fiber Types

Muscle Fiber Types

The human body is built with three types of muscles- cardiac, smooth, and skeletal. Skeletal muscles form most of the human body, and muscle fibers are muscle cells that make up the skeletal muscles. These cells are called myocytes. They mainly control physical forces moving through the whole body.

Muscle fiber types are majorly categorized into two types- Type I and Type II. The Type I muscle fibers are known as slow-twitch muscles, and the Type II muscle fibers are known as the fast-twitch muscles. The fast-twitch muscle fibers have subcategories as well.

Slow Twitch Muscle Fibers

Slow-Twitch muscle fibers are the smallest muscle fibers, thus grow less compared to the others. It is known as slow oxidative muscle fibers, and its strong dependence on oxygen is the reason for the term oxidative. They use aerobic metabolism to create fuel for muscle activity. These fibers come into action in our regular activities, activities which are typical and low in intensity.

Walking, jogging, less intense resistance workouts and other similar activities use slow-twitch muscle fibers. These types will not grow with endurance-focused strength; instead, go for aerobics, and that will work better. They do not fatigue soon, so they can efficiently help the athletes and bicycle riders continue marathon for long hours.

Fast Twitch Muscle Fibers

Fast-twitch muscle fibers are good for those activities which need quick force. They use long-term anaerobic metabolism to create fuel and is capable of coming into action during intense activities and high resistance workout, activities which require too much power at a time.

Unlike the Type I, these fibers fatigue quickly, which is a massive drawback for athletes who cannot afford tired muscles rapidly. However, for squats, long jump, sprinters, fast-twitch muscle fibers are a boon as an athlete needs a certain amount of energy to jump or run a certain distance.

  • Fast-twitch has two subcategories- Type IIa and Type IIb.
  • Type IIa is a combination of both slow-twitch and fast-twitch muscle fibers as it can use both aerobic and anaerobic metabolism to create fuel for energy.
  • Type IIb, on the other hand, is the classic fast-twitch muscle fibers which only use anaerobic metabolism to get the required energy for applying intense force.

What’s Your Muscle Fiber Type

Now the question arises that what type you are. There is no 100% guaranteed scientifically approved way to know the type of your muscle fibers. However, a biopsy might give you a hint. The biggest clue you can get is from doing your own activities.

If you are doing exercises or playing sports for long hours without getting tired but seeing no growth in your muscles, then you are Type I, and if you grow muscles at a relatively less time and get worn too soon, then you are Type II. Remember, it’s just a guess not conformed.

How They Affect

The type of fibers cannot be interchanged, but the amount of the area can with a variation of training. As we have already talked about endurance level and fatigue, it is pretty obvious that both the muscle types have their fair share in affecting our workouts. We already have got a hint that Type I offers endurance, and Type II offers power. So, to get the desired result, you have to opt for a particular exercise that will hit the targeted muscle fiber.

For muscle growth, you need to hit your slow-twitch muscle fibers with higher repetition and lesser weight. In the case of the fast-twitch muscle fibers, you need to try lower repetitions and higher weight. They are the best combination of fast muscle growth.

Muscle fiber types are not constant. The human body is so complicated and diverse that none of the two are the same. So, don’t judge your body type relying on others. Understand what your body needs for proper muscle growth. A little bit of knowledge and the help of professionals will make your job easy.


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