Table of Contents
Muscle Fiber Types
Time To Peak Power
Type I (slow twitch)
Type IIA (fast twitch oxidative fibres)
Type IIB (fast twitch glycolytic fibres)
- Type I fibers are characterized by low force/power/speed production and high endurance, The slow twitch muscle fibers are more efficient at using oxygen to generate more adenosine triphosphate (ATP) fuel for continuous, extended muscle contractions over a long time. They fire more slowly than fast twitch fibers and can go for a long time before they fatigue. Therefore, slow twitch fibers are great at helping athletes run marathons and bicycle for hours.
- Type IIB fibers are characterized by high force/power/speed production and low endurance. These fast twitch fibers use anaerobic metabolism to create energy and are the “classic” fast twitch muscle fibers that excel at producing quick, powerful bursts of speed. This muscle fiber has the highest rate of contraction (rapid firing) of all the muscle fiber types, but it also has a faster rate of fatigue and can’t last as long before it needs rest. These fibers are the ones that are most involved when we perform a maximum repetition.
- Type IIA fibers fall in between the two. These fast-twitch muscle fibers are also known as intermediate fast-twitch fibers. They can use both aerobic and anaerobic metabolism almost equally to create energy. In this way, they are a combination of type I and type IIB muscle fibers.