Which type of muscle fiber is characterized by fast contraction speed and high force production?

The type of muscle fiber that is characterized by fast contraction speed and high force production is the Type IIb fast glycolytic fiber. These fibers have a greater diameter than slow-twitch fibers and are designed for explosive, high-intensity activities. They rely primarily on anaerobic metabolism, which allows them to generate energy quickly for short bursts of activity, such as sprinting or heavy lifting. This is due to their high concentration of glycogen and ability to produce ATP rapidly through glycolysis.

Additionally, Type IIb fibers fatigue quickly because they are not as efficient at using oxygen and have a limited supply of endurance. Their fast contraction speed is ideal for activities that require power and strength, distinguishing them from slow-twitch fibers that are more suited for endurance and prolonged activities. Intermediate fibers possess characteristics of both, but they do not achieve the same levels of speed and force production as Type IIb fibers, while Type I fibers are more focused on endurance and slow contraction speed.