Newton's 2nd law: The acceleration of an object varies directly as the external unbalanced force applied to it and inversely as its mass.
This law occurs in gymnastics because the gymnasts mass varies depending on how short or tall you are. The less mass a gymnast has, the faster she will run and do a tumbling pass and the faster the acceleration will be. With a gymnast that has more mass, the slower they will accelerate and the slower they will run. Another way to look at it is, when a shorter gymnast may not be able to put as much force in her running than the heavier gymnast. The lighter the gymnast, the the lighter the mass is and the lighter the force is. The heavier the gymnast is, the heavier the mass and force is.