Muscle function differs between slow-twitch and fast-twitch fibers in terms of energy usage and endurance. Slow-twitch fibers, predominately used in endurance activities, rely on aerobic metabolism, allowing for sustained energy over longer periods. They excel in activities like distance running and cycling. Fast-twitch fibers, on the other hand, are anaerobic and designed for short bursts of strength and speed, engaging in activities like sprinting and heavy lifting. Both fiber types are crucial for athletic performance and training, each serving distinct purposes.