Muscle Fiber. Types

The human body is a fantastic organism that continues to amaze scientists with the features of its device for many centuries. However, even the previously explored body parts are fraught with many amazing features. This essay aims to study the human’s muscle tissue both in general and at the molecular level.

First of all, it is necessary to note diversity and a large number of muscle types. In general, three types of fibers are commonly distinguished: slow-oxidative type I, fast-oxidative glycolytic type IIA, and fast glycolytic type IIX (Wilson et al. 2012). Type I specializes in sustained activities that require a lot of stamina and thus is most developed in marathon runners. However, types IIA and IIX, due to their rapid contractile activity, can generate much more power (Wilson et al. 2012). The development of these muscles in weightlifters and people who specialize in high power loads confirms this fact. These individuals have the most developed type IIA muscles, which have a peak power ten times that of type I.

The reasons for this difference are primarily due to the molecular structure of each muscle type. Type I, in contrast to type II, has a much higher volumetric density of mitochondria, while at the same time having an increased contact length of capillary fibers (Wilson et al. 2012). These features allow oxygen to be used as the primary source of energy for muscular activity. Muscles of the second type either burn the incoming oxygen extremely quickly or use glycolysis as an alternative power source. Both options allow getting more power at the expense of extra energy consumption. Additionally, various types of muscle have different molecular structures of myosin isoforms responsible for generating force (Miller et al. 2015). The more type II myoforms in muscle tissue, the larger amount of power it can produce.

The features described above allow analyzing the ratio of different types of muscles and their impact on human productivity. Type I is more commonly used by individuals involved in endurance-focused sports, while Type II muscles are better developed in weightlifters (Wilson et al. 2012). However, no athlete can neglect the development of all types of tissues, since it is their ratio that is important. Studies have shown that untrained people have approximately the same proportion of both types of muscle fibers (Wilson et al. 2012). Marathon athletes have up to 90 percent Type 1 muscle, which allows them to perform long endurance exercises using the slow conversion of oxygen to energy. On the other hand, sprinters are dominated by type II muscle fibers by up to 80 percent. This ratio allows them to burn the stored energy as efficiently and quickly as possible, giving the maximum potential result in a short time.

Finally, the features of the structure and work of muscle fibers can be analyzed not only by the example of humans but also by other species, such as chimpanzees. Their increased strength compared to humans has been known for many years. The essence of these differences also lies in the ratio of different types of tissue in chimpanzees. Their structure is the predominance of fast-twitch muscles since their rate is approximately 67 percent (O’Neill et al. 2017). Due to this, an ordinary chimpanzee is about one and a half times stronger than an average person, since it has a more significant peak power.

Thus, humans and other creatures’ ability to perform specific actions can be analyzed in terms of muscle function. Types of muscle fibers are classified according to their molecular structure, allowing more or less active absorption of energy. Besides, the proportions following which these types of tissues are developed are of great importance. Depending on which activity is predominant, an increased number of muscles of a specific type is observed in the human body. This trend extends not only to humans but also to other species, such as chimpanzees.


Miller, Mark., Nicholas Bedrin, Philip Ades, Bradley Palmer, and Michael Toth. 2015. “Molecular Determinants of Force Production in Human Skeletal Muscle Fibers: Effects of Myosin Isoform Expression and Cross-Sectional area.” American Journal of Physiology-Cell Physiology 308 (6): C473-C484.

O’Neill, Mattew, Brian Umberger, Nicholas Holowka, Susan Larson, and Peter Reiser. 2017. “Chimpanzee Super Strength and Human Skeletal Muscle Evolution.” Proceedings of the National Academy of Sciences, 114 (28): 7343-7348.

Wilson, Jason, Jeremy Loenneke, Edward Jo, Gabriel Wilson, Michael Zourdos, and Jeong-Su Kim. 2012. The Effects of Endurance, Strength, and Power Training on Muscle Fiber Type Shifting. The Journal of Strength & Conditioning Research, 26 (6): 1724-1729.

"Looking for a Similar Assignment? Order now and Get a Discount!

Place New Order
It's Free, Fast & Safe

"Looking for a Similar Assignment? Order now and Get a Discount!