Since the tendency of an edge is toward the center of the circle created by that edge, a skater's upper body, arms, and free leg also have a tendency to be pulled along by the force of the edge. If the upper body, arms, and free leg are allowed to follow passively, they will eventually overtake the edge's rotational edge and will rotate faster, a principle that is also used to create faster spins. The inherent force of the edge and the force generated by a skater's upper body, arms, and free leg tend to increase rotation, so successful jumping requires precise control of these forces. Leaning into the curvature of the edge is how skaters regulate the edge's inherent angular momentum. His or her upper body, arms, and free leg are controlled by what happens at the time of preparation for the jump and its take-off, which are designed to produce the correct amount of rotation on the take-off. If the skater does not have enough rotation, he or she will not be at the correct position at the take-off; if he or she rotates too much, the upper body will not be high enough in the air. Skaters must keep track of the many different movements and body positions, as well as the timing of those movements relative to each other and to the jump itself, which requires hours of practice but once mastered, becomes natural.