How Skeletal Muscle Fiber Types Influence Athletic Performance

How Skeletal Muscle Fiber Types Influence Athletic Performance

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How Skeletal Muscle Fiber Types Influence Athletic Performance

Myocytes are bundles of individual muscle fibers that make up the skeletal muscle. Every myocyte contains numerous strands of protein (myosin and actin) known as myofibrils. These myofibrils pull and grab onto each other, prompting muscle contraction and shortening the muscle. Generally, it is accepted that muscle fiber can be categorized into two broad types, namely the slow-twitch (type I) muscle fibers and fast-twitch (type II) muscle fibers. The latter can be further classified into type IIa and type fibers. These categorizations tend to influence the way muscles respond to physical activity and training, and every fiber type has a unique contracting ability. The muscles of human beings contain both slow and fast fiber types. This essay discusses how skeletal muscle fiber types influence athletic performance.

Slow-twitch muscle fibers tend to be fatigue resistant and focused on postural control and small and sustained movements. They contain myoglobin and mitochondria. Also, compared to fast-twitch fibers, slow-twitch muscle fibers are more aerobic. They are, at times, referred to as red fibers because they supply blood. Slow-twitch muscle fibers tend to be more efficient at generating adenosine triphosphate (ATP) using oxygen for continuous muscle contractions over a long period of time (Begue, Raue, Jemiolo, & Trappe, 2017). Compared to fast-twitch muscle fibers, slow-twitch muscle fibers last longer before fatigue. Due to this, slow-twitch fibers are beneficial in assisting athletes bicycling for hours and in running marathons.

Type II fast-twitch muscle fibers are better at developing short bursts of speed or strength because they generate fuel using anaerobic metabolism. On the downside, fast-twitch muscle fibers get fatigued faster. Generally, fast-twitch fibers tend to use the same force in every contraction, but their name is derived from their ability to fire more rapidly than the slow muscle fibers. Fast-twitch muscle fibers give more powerful and bugger forces but over a shorter duration than their counterparts. They have less blood supply and are more anaerobic. Skeletal muscles contain both slow and fast fiber muscles and the radio is dependent on a variety of factors, including age, function, and training. Type IIa fast-twitch muscle fibers have the ability to use anaerobic and aerobic metabolism in equal measures to generate energy. Type IIa fast-twitch muscle fibers are also referred to as intermediate fast-twitch fibers. Type IIb, fast-twitch fibers employ anaerobic metabolism to form energy. They are classic type II fast-fiber muscles excelling at producing powerful and quick bursts of speed. Compared to its counterpart, the fast-twitch muscle fiber does well at producing powerful and quick-speed bursts. Additionally, the fast-twitch muscle fibers have the highest contraction rates compared to all other muscle fiber types. Similarly, they have a faster fatigue rate compared to slow-twitch muscle fibers and tend to go long without needing rest.

The type of muscle fibers that people have informs the kind of sports a person is naturally good at and whether they are strong or fast. Athletes find themselves on that part mainly because of their genetic makeup. Olympic sprinters have been found to have about 80% of fast-twitch fibers and those that do well in marathons possess about 80% of slow-twitch fibers (Książek, Zagrodna, & Słowińska-Lisowska, 2019). While fibers is an excellent determinant of athletes’ success, along it is a poor determinant of performance. Other factors that inform athleticism are proper nutrition and hydration, mental preparedness, enough rest, and appropriate conditioning and equipment.

In closing, human skeletal muscle fibers are categorized into two slow-twitch muscle fibers and fast-twitch muscle fibers. Fast-twitch muscle fibers are further categorized into type IIa and type IIb fast-twitch muscle fibers. While fast-twitch muscle fibers support powerful and quick movements like weightlifting and sprinting, slow-twitch muscle fibers support long-distance activities such as running a marathon. While athletic abilities are genetic informed, muscle fibers tend to develop more and improving their coping ability to stress with consistent endurance training.


Begue, G., Raue, U., Jemiolo, B., & Trappe, S. (2017). DNA methylation assessment from human slow-and fast-twitch skeletal muscle fibers. Journal of Applied Physiology, 122(4), 952-967.

Książek, A., Zagrodna, A., & Słowińska-Lisowska, M. (2019). Vitamin D, skeletal muscle function and athletic performance in athletes—A narrative review. Nutrients, 11(8), 1800.

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