"Slow-twitch" refers to a type of muscle fiber that is designed for endurance activities. These fibers contract slowly and can sustain activity for long periods without getting tired. They are rich in mitochondria, which help produce energy efficiently, making them ideal for activities like long-distance running or cycling. Athletes who rely on slow-twitch fibers often excel in endurance sports. For example, marathon runners and swimmers benefit from these fibers because they allow them to maintain a steady pace over long distances. In contrast to fast-twitch fibers, which are better for short bursts of speed, slow-twitch fibers support prolonged physical effort.