Do marathon runners use fast twitch or slow muscles?

Marathon runners primarily use slow twitch muscle fibers, also known as Type I muscle fibers. These muscle fibers are well-suited for endurance activities such as marathons due to their ability to generate sustained force for long periods. Slow twitch fibers have a high concentration of mitochondria, which produce energy through the aerobic metabolism of fatty acids and carbohydrates. They are fatigue-resistant and can maintain a steady pace for long distances, making them ideal for the endurance demands of marathon running.

Fast twitch muscle fibers, or Type II muscle fibers, are better suited for short, explosive bursts of activity. They generate force quickly but fatigue more easily. Marathon runners may use fast twitch fibers to a lesser extent during the initial acceleration or sprint finish, but they are not primarily responsible for the sustained effort required to complete a marathon.