Which muscle fibers are primarily recruited during marathon running?

Type 1 muscle fibers, also known as slow-twitch fibers, are primarily recruited during marathon running due to their unique characteristics that align with the demands of endurance activities. These fibers are highly efficient at using oxygen to generate energy through aerobic metabolism, which is essential for prolonged, steady-state activities like distance running.

Type 1 fibers are fatigue-resistant and can sustain activity over extended periods without quickly depleting energy stores, making them ideal for marathon runners who require endurance to maintain a steady pace throughout the race. They also have a higher capillary density, increased mitochondrial content, and greater oxidative enzyme activity, which supports sustained aerobic energy production.

In contrast, other muscle fiber types such as Type 2x and Type 2a are more relevant to short bursts of high intensity and power output rather than the endurance needed for activities like marathon running. Type 2x fibers, for instance, are designed for explosive strength and fatigued quickly, while Type 2a fibers can perform both aerobic and anaerobic activities but are not the predominant fibers utilized in prolonged endurance efforts.