M4 Jump drive, flight and landing

Topic

In general, an athlete's jump converts the mechanical energy generated during the ground-based propulsion phase into the kinetic and potential energy of the center of mass during the subsequent flight phase.

In a vertical jump, conversely, the final height reached depends solely on the vertical velocity of the center of mass at the moment of takeoff—a height also defined by another model in this set based on the center of mass's flight trajectory.

This stretch-shortening cycle—when preceded by a countermovement—can increase the jump's final height compared to an equivalent static jump (a comparison also established by another model in this set). This increase results from both the greater contribution of elastic energy from the athlete's tendons and muscles and additional reflex potentiation.

The net impulse of the jump—calculated as the area under the ground reaction force curve minus the athlete's body weight—is exactly equal to the change in the center of mass's momentum at takeoff; this impulse is also defined in another model in this set as the integral of the ground reaction force over time.

Consequently, this model—based on the energy conversion between the propulsion and flight phases—demonstrates that in a long jump, an optimal takeoff angle maximizes the jump's distance; this is the same takeoff angle identified in another model in this set as the cause of dynamic mode failure when the angle is incorrect. Conversely, the athlete absorbs the final energy of the jump during landing through the eccentric action of the knee and ankle extensors—specifically, the type of eccentric contraction that defines this particular model of skeletal muscle function. If the athlete's takeoff angle deviates further from the optimal angle established by the model, the final distance of the long jump is consequently reduced even more.

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