Fast-twitch muscle fibers are a type of muscle fiber that contract quickly and generate a lot of force. They are primarily used for short bursts of intense activity, such as sprinting or weightlifting. These fibers rely on anaerobic metabolism, which means they do not need oxygen to produce energy, allowing for rapid energy release. Unlike slow-twitch muscle fibers, which are more endurance-oriented, fast-twitch fibers fatigue quickly. They are important for athletes in sports that require speed and power, such as track and field or football. Training can enhance the performance of these fibers, improving overall athletic ability.