The vertical height of clearance is dependent on 3 main phases, The Takeoff Phase, The Flight Phase, and The Landing Phase.
The amount of angular momentum created is the Takeoff Phase. The ability to control rotation and translation of the center of mass is the Flight Phase. The ability to land safely and absorb momentum in an aesthetically pleasing way is the landing phase.
The most important phase of a box jump is the takeoff phase. In this phase, we are creating angular momentum that will be transferred into the vertical jump. Key considerations for creating speed and angular momentum in takeoff are the mobility and stability of the hip, knee, and ankle joints. The actual jump itself results from powerful extension of the knee, hip, and ankle joints, supplemented by a forward and upward swing of the arms. The main objective here is to get the body’s center of mass as high as possible in preparation for flight phase.
The magnitude, angle, takeoff speed, and air resistance at takeoff dictate the amount of angular momentum generated in the flight phase. There are 2 main techniques while in the air: The sail and the hitch kick. The sail occurs from the moment the feet have left the ground until the hips begin to flex for the hitch kick. The hitch kick helps to position the center of mass underneath the body, control rotation and translation for landing phase, and to do this in an aesthetically pleasing way.
The important factors for landing are body position and actions upon landing. Body positions and actions that lead to a safe and accurate landing are:
- Forward lean of the trunk helps increase landing time
- Control of Rotation and Translation using the core muscles
- Landing soft through bent knees flexed no more than 90 degrees
- Absorbing momentum through the heels activating the posterior chain.
The key to remember here is that the most important phase is the Takeoff Phase. The most important aspects of the Takeoff Phase are ankle, hip, and knee extension with an upward/forward swing of the arms. Extension of the hip, knee, and ankle joints is heavily determined by joint mobility.