Which type of motor units are primarily recruited during endurance activities?

During endurance activities, slow twitch motor units are primarily recruited due to their capacity for sustained activity over longer periods. These motor units consist of Type I muscle fibers, which have a higher endurance capability because they utilize aerobic metabolism to generate energy. This allows them to resist fatigue, making them ideal for prolonged activities like distance running, cycling, or swimming.

Slow twitch motor units have a rich supply of oxygen and are equipped with numerous mitochondria, enabling effective oxygen utilization and energy production. This characteristic is crucial for activities that require endurance, as they can sustain contractions for extended durations without quick fatigue. In contrast, fast twitch motor units, which are responsible for explosive movements and high-intensity efforts, rely more on anaerobic processes and fatigue more quickly, making them less suitable for endurance activities. Therefore, slow twitch motor units effectively meet the demands of endurance exercise by providing the necessary stamina and consistent energy supply.