What type of muscle fiber is primarily used during endurance activities?

Type I fibers, also known as slow-twitch fibers, are primarily utilized during endurance activities. These fibers are characterized by their high oxidative capacity, meaning they efficiently use oxygen to generate energy through aerobic metabolism. This makes them ideal for prolonged activities such as distance running, cycling, and swimming, where energy demands are sustained over an extended period.

Additionally, Type I fibers have a rich supply of blood vessels and a greater number of mitochondria, which enhance their ability to respond to the energy needs of long-duration activities. They fatigue more slowly than other fiber types, allowing athletes to maintain performance during extended exercise bouts. Overall, the endurance capacity of Type I fibers is what distinguishes them as the primary muscle fiber type engaged in endurance sports.