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Different muscle fibers

Muscles, muscle fibers, or muscle cells come with different properties, some are fast, some are slow, some are good under anaerobic conditions,
and some are better under aerobic conditions. We can identify some of these properties with Histochemical staining.

Fiber construction of the extensor digitorum longus muscle, also known as EDL and the soleus muscle. Both muscles are found in the lower part of the leg. The graph illustrates the two types of muscles on the x-axis and the fiber composition measured in percentage on the y-axis. The graph illustrates two columns; a column to the left, consisting of the different fibers in the EDL muscle and a column to the right consist of the different fibers in the soleus muscle. The EDL column shows that the EDL muscle is composed of type one, type two A and type two B fibers. Over 60 percent of the fibers are type two B, approximately 20 percent of the fibers are type two A and the rest is type 1. The soleus column shows that the soleus muscle is composed of type 1 and type two A fibers, where around 80 percent of the fibers are type 1

Fig.1 Types of muscle fibers in the EDL and Soleus muscle

There are two broad groups of muscle fibers:

Type I (1) is a slow twitching type, with a high relative concentration of mitochondria,
excellent for slow and prolonged activities such as walking.

Type II (2) is a fast-twitching type, optimized for fast and shorter duration activities such as sprinting.
Type II muscle fibers are further divided into two different categories, IIA and IIB.

Type IIA fibers are fast oxidative muscle fibers, better for activities such as longer sprints.

Type IIB muscle fibers are glycolytic, meaning they are good at anaerobic exercises such as quick but very short sprints.