Slow-twitch muscle fibers, also known as type I fibers, are specialized for endurance activities. They contract slowly and can sustain activity for long periods without fatigue. These fibers are rich in mitochondria and myoglobin, which help them efficiently use oxygen for energy. This makes them ideal for activities like long-distance running and cycling. Athletes who engage in endurance sports often have a higher proportion of slow-twitch fibers. In contrast to fast-twitch fibers, which are better for short bursts of power, slow-twitch fibers support prolonged, steady efforts. Training can enhance the efficiency and performance of these fibers, benefiting endurance athletes.