Which factor is not listed as a determinant of vertical jump height?

• A. Arm swing
• B. Approach velocity
• C. Force production
• D. Speed of contraction

Answer: (D)

Vertical jump height is driven by the impulse generated during the takeoff. Impulse comes from how much force you can produce and how quickly you can apply it within the brief contact time of the jump, so factors that enhance this impulse directly influence how high you jump.

Arm swing helps because sweeping your arms upward during the jump adds to the vertical impulse, effectively boosting the total lift you can achieve. A quicker, well-timed countermovement also taps into stored elastic energy and helps you develop greater force during the push-off. Approach velocity matters too: starting the push-off with some forward speed increases the kinetic energy you can transform into vertical lift, again contributing to a higher jump.

Force production is obviously central because the greater the force you can generate during the push-off, the larger the impulse and the higher the jump.

Speed of contraction, on the other hand, isn’t typically listed as a determinant. While how fast muscles shorten relates to how quickly force can be developed, the relationship is governed by the force–velocity curve, and contraction speed alone doesn’t predict jump height. What matters more is how rapidly and how much force you can develop at takeoff (rate of force development) within the available contact time.