Final answer:
A sprinter experiences muscle fatigue before a marathon runner due to anaerobic metabolism that leads to lactic acid build-up, whereas marathon runners use aerobic metabolism and have more slow-twitch muscle fibers that enhance endurance.
Step-by-step explanation:
A sprinter would experience muscle fatigue before a marathon runner due to anaerobic metabolism in the muscles of the sprinter. Sprinting is a high-intensity, short-duration exercise that requires a quick energy release that aerobic metabolism cannot supply fast enough. Therefore, the sprinter's muscles rely on anaerobic metabolism, which leads to the production of lactic acid and a rapid onset of fatigue. On the other hand, a marathon runner's muscles are adapted for endurance and utilize aerobic metabolism, allowing them to sustain activity for a longer period due to a higher proportion of slow-twitch fibers, which have more capillaries, mitochondria, and myoglobin.
These endurance adaptations enable marathon runners to carry more oxygen and maintain aerobic activity, leading to reduced muscle fatigue during prolonged periods of exercise. Furthermore, muscle fatigue in sprinters is intense due to the nature of the fast-twitch fibers that are designed for quick bursts of speed but not for endurance, resulting in a faster build-up of lactic acid when compared to the slow-twitch fibers prevalent in marathon runners.