During a typical tennis game, the foot undergoes every conceivable type of stress. At the serve, it must create a stable base from which the upper body can "wind up" from, then spring forward to take an optimal court position. The rapid changes in direction alternate the loads on the foot from heel to toe and the outside and inside of the foot. Upstep custom-made orthotics are essential as they stabilize the foot but don’t restrict its ability to change direction quickly due to them being made to match your own foot.