Different distances require further refinements. A sprinter takes off and stays on the ball of his foot and so needs little cushioning in the heel or even middle of the foot, but lots in the front. A middle-distance runner has more of a midfoot-to-toe stride (or even a less efficient heel-to-toe stride), and so needs maximum spring at midfoot and heel. Marathoners also need heel cushioning but as little weight as possible: for them, a tongueless shoe.
