Why are female track runners so big?

Sometimes at the adult professional level the working out/running/practice builds muscle m rather than keeping a woman lean. Plus track athletes tend to be very tall and big for power (sprinters). It also depends on the woman -- the running either leans them out or puts muscle m on them. The taller a hurdler is the better able they are to get over the hurdle. The upper bodies are also big from running. Lastly, serious track athletes often begin missing their menstrual periods during training and hormone disturbance may play a role in muscle m.