Skeletal Muscle Fibre Types And Their Characteristics

There are three types of muscle: Type I (slow-oxidative), Type IIA (fast-oxidative) and Type IIB (fast-glycolytic).

Different types are necessary for excelling in different sorts of exercise. For example, Type I (slow-oxidative) is highly resistant to fatigue, and endurance athletes such as marathon runners have slow muscle fibres in around 82% of their muscles.

Type II muscle fibres (fast-oxidative and fast-glycolytic) on the other hand, primarily use anaerobic metabolism, meaning they don’t require oxygen to be used.

These fibers fatigue easily and are hence heavily relied on by sprinters and weight lifters who don't require extensive use from these muscles. Weightlifters have 55% fast fibres in their skeletal muscular systems.

Sprinters are commonly seen to hold their breath for the 10 seconds it takes them for the 100m sprint because these types of muscles do not require oxygen.

These different muscle types can be seen by just looking at a marathon runner and a sprinter and comparing their physique.