There are five physiological adaptations that happen as a result of 2 hour-long runs. 

One is that your circulatory system, particularly the fine capillaries, develops to circulate blood to exercising muscles and the second adaptation is that you teach your body to more readily metabolize fat and burn fat at your aerobic base. Three, lung efficiency is greatly improved to bring more oxygen to your mussels. Time on your feet helps your body adapt to the distance and get stronger.