Muscle Fiber Ratios Explained

Photo by: Bigstockphoto
Photo by: Bigstockphoto

What are muscle fiber ratios and why are they relevant to your fitness goal? The human body is composed of muscle tissues. Each of these muscle tissues corresponds to various types of fibers. These muscle fibers utilize different energy sources. They are also activated differently according to the type of exercises you choose.

There are three types of muscle fibers: slow oxidative fibers, fast oxidative gylolytic fibers, and fast glycolytic fibers. Every muscle in your body possesses all three varieties of muscle fibers. But the amount will according to muscle groups and by an individual.

How Muscle Fiber Ratios are Calculated

Muscle fiber ratio is the measurement of the proportions of muscles in the human body. It measures the muscle fiber’s ratio, according to different muscle types. And the proportions of the muscles will differ on genes and the type of exercise you use to activate certain muscles.

Muscle fiber ratio is the measurement of the relative amount of slow oxidative or slow-twitch fibers to the combined number of fast oxidative glycolytic and fast glycolytic fibers. To calculate the fiber ratios, the fast oxidative glycolytic and fast glycolytic fibers are categorized together as fast-twitch muscles. The measurements are expressed as percentages.

Types of Muscle Fibers

Slow-Twitch Dominant Muscles

Some muscle groups work together to fight gravity and maintain an erect posture. These muscles consume more oxygen because they have to sustain contractions for an extended period of time without fatigue. These muscles are called slow-twitch dominant muscles. These are highly flexible, extremely strong muscles with a high ratio of slow twitch fibers to fast-twitch fibers. However, slow-twitch dominant muscles do not contract as quickly as other muscle groups.

Fast-Twitch Dominant Muscles

Fast-twitch dominant muscles allow movements that require rapid force or powerful contraction. These muscles perform fast, explosive movements for a short time. The muscle tires easily because it consumes more glycogen and ATP energy, which are easily depleted resources. Usually, fast-twitch dominant muscles have a low ratio of slow- to fast-twitch fibers.

Exercising According to Fiber Ratios

Different types of strength training moves and exercises work to change the fiber ratios of specific muscle groups. For example, exercises that demand a higher level of endurance and stamina – such as distance running or cycling – tones muscles with a higher slow- to fast-twitch fiber ratio.

On the other hand, exercises that require explosive energy and power in short bursts – like sprinting and power lifting – activate fast, explosive muscle movements result in a lower slow- to fast-twitch fiber ratio in target muscles.

Now, depending on your workout routine, weight lifting can either lower or raise your slow- to fast-twitch fiber ratio. If you lift heavy weights with few reps, the muscles’ ratio will decrease. Also, performing lighter weight lifting with more reps per session will decrease the muscle fiber ratio as well.

If you are working with a professional trainer, it’s important to let your trainer know what kind of results you expect. This way, your trainer can develop the right fitness plan that could either boost or decrease muscle fiber ratio. Know that the kind of workout that suits you will depend on your own fitness goal.


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