Human skeletal muscles are composed of two different types of muscle fiber. White muscle fibers, called fast‐twitch or type-II fibers can generate bursts of speed and power. Red muscle fibers, called slow-twitch or type I-fibers have a strong resistance to muscle fatigue.
Most people have a more or less equal distribution of fast-twitch and slow-twitch fibers. But some people have a lot more fast-twitch fibers, which means they are born to excel in explosive sports. Others have a lot more slow-twitch fibers, making them destined to become endurance athletes.
This muscle fiber type distribution is largely genetically determined and is only to a small extent trainable. An athlete’s personal muscle typology can be used for early talent identification and is also a crucial factor to consider when designing individualized training, so as to optimize muscle potential and minimize risk of injuries. Knowing what an athlete’s body is made of and where their talent lies is therefore important information for athletes and their trainers and medical crew.