Biomechanical Model Landing.txt

A slower linear speed when the body collides with the ground will reduce the vertical ground reaction force and the friction force. This reduces the external forces that slow the body down and reduces the sum of joint forces that the body must absorb.

Your body will collide with the ground with the same speed it leaves the ground. If the objective of the jump is maximum vertical height or horizontal distance, then the linear speed when your body collides with the ground will be the largest linear speed you were able to create when you left the ground.

Therefore, decreasing the linear speed when you collide with the ground is not a viable method for reducing the external forces applied to the body when it collides with the ground.

A longer application time of each external force that slows the body down will reduce the vertical ground reaction force and the friction force. This reduces the external forces that slow the body down and reduces the sum of joint forces.

When landing after a VERTICAL JUMP, 4 real-world actions must be performed in order to increase the application time of the external forces slowing the body down:

(1) initial contact must be on the forefoot 

(2) the ankle joints should be maximally plantar flexed prior to contact with the ground

-upon contact with the ground, the ankle plantar flexor muscles should be contracted to create eccentric ankle dorsiflexion torques

(3) the knee joints should be slightly flexed prior to contact with the ground

-upon contact with the ground, the knee extensor muscles should be contracted to create eccentric knee flexion torqes

(4) the hip joints should be slightly flexed prior to contact with the ground

-upon contact with the ground, the hip extensor muscles should be contracted to create eccentric hip flexion torques

When landing after a HORIZONTAL JUMP, initial contact is made with the heels. 3 real-world actions must be performed in order to increase the application time of the external forces slowing the body down:

(1) the ground that you land on should be soft

-this will allow the heels to continue to move while you perform real-world actions 2 and 3. 

(2) the knee joints should be slightly flexed prior to contact with the ground

-upon contact with the ground, the knee extensor muscles should be contracted to create eccentric knee flexion torques

(3) the hip joints should be slightly flexed prior to contact with the ground

-upon contact with the ground, the hip extensor muscles should be contracted to create eccentric hip flexion torques

A smaller body mass when the body collides with the ground will reduce the vertical ground reaction force and the friction force. This reduces the external forces that slow the body down and reduces the sum of joint forces that the body must absorb.

Short-term for body component mass:

(1) wear the lightest clothing possible

(2) wear the lightest shoes possible

Long-term for body component mass:

(3) lose fat mass

A smaller coefficient of friction when the body collides with the ground will reduce the friction force. This reduces an external force that slows the body down and reduces the sum of joint forces that the body must absorb.

Theoretically, we could make the material of the shoe harder and the surface of the material smoother. This would decrease the magnitude of the friction force that slows you down.

Unfortunately, the real-world application is something very different.

Decreasing the coefficient of friction will have no affect on the magnitude of the friction force slowing you down until you reduce it to a level that would allow the shoe to slip