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Vertical Ground Reaction Force
to create a larger vertical ground reaction force you must run on the hardest surface available
Coefficient of Friction
To create a larger coefficient of friction, the bottom surface of the shoes that you are wearing must have two characteristics:
(1) the material of the soles must be soft
(2) the surface of the soles must be rough
To create a larger muscle force, three factors that influence the size of the muscle force must be considered.
(1) muscle size (increase via training)
(2) muscle length (120% = most muscle force)
(3) speed of muscle contraction (contracted slower = more muscle force)
Muscles Involved in Running
(fix this card)
- fibularis longus
- fibularis brevis
- tibialis posterior
- gluteus maximus
- rectus femoris
- tensor fasciae latae
- adductor magnus
- biceps femoris
- gluteus maximus
- gluteus medialis
- gluteus minimus
The distance from the joint's axis of rotation to the line of pull of the muscle force.
To increase the moment arm distance, you would need to move the line of pull of the muscle force further away from the joint's axis of rotation.
One method for moving the line of pull of the muscle force would be to change the locations of the origin and insertion points for the muscle. This is not an option because it would be unethical to perform this type of surgery.
The only way we can change the moment arm distance is by changing the angle of the joint.
Short-term for body component mass
(1) wear the lightest clothing possible
(2) wear the lightest shoes possible
Long-term for body component mass
(1) lose fat mass
Radius of Resistance
The distance from the joint's axis of rotation to the center of mass of the body component.
The length of the radius of resistance is determined by bone length and joint orientation. There is nothing we can do to decrease bone length.
However, similar to changing the moment arm distance, we can shorten the radius of resistance by changing the angles of the joints with the body component being rotated.
Any change in a joint angle that brings a portion of the body component closer to the axis of rotation will shorten the radius of resistance.
Application Time of Each Joint Torque
For the ankle:
(1) During the preparation phase, the ankle must be dorsiflexed
(2) During the execution phase, a concentric ankle plantar flexion joint torque is applied until the ankle is maximally plantar flexed
For the knee:
(1) During the preparation phase, the knee must be flexed
(2) During the execution phase, a concentric knee extension joint torque is applied until the knee is maximally extended
For the hip:
(1) During the preparation phase, the hip must be flexed
(2) During the execution phase, a concentric hip extension joint torque is applied until the hip is maximally extended
Radius of Rotation
The distance from the joint's axis of rotation to the point of interest on the body component.
The length of the radius of rotation is determined by bone length and joint orientation. There is nothing we can do to increase bone length.
However, similar to changing the moment arm and the radius of resistance, we can change the radius of rotation by changing the angles of the joints within the body component being rotated.
Any change in a joint angle that rotates a portion of the body component farther from the axis of rotation will lengthen the radius of rotation.
During running, the fluid you are moving through is air.
There are three atmospheric conditions that would reduce fluid density:
(1) higher altitude
(2) lower humidity
(3) warmer temperatures
Coefficient of Drag
A measure of the surface friction between the surface of the runner and the air as the runner moves through the air.
The coefficient of drag may be reduced by making the surface of the runner smoother.
This can be accomplished in 3 ways:
(1) any clothes that are worn must be made of materials that are extremely smooth
(2) worn clothes must be tight-fitting
(3) uncovered areas of the body should have the body hair removed
Area of Drag
A measure of the area of turbulent air behind the runner as the runner moves through the air.
The area of drag may be reduced by making the area of turbulent air behind the runner smaller.
There are 2 primary mechanisms for reducing the area of turbulent air behind the runner:
(1) make the area of the runner that collides with the air smaller
(2) have the runner run in an aerodynamic position
Unfortunately, neither of these 2 mechanisms can be implemented during running.
The primary method for making the area that collides with the air smaller is to reduce the height and weight of the runner. Doing either of these would affect the speeding up side of the model.
For these reasons, nothing can be done to reduce the area of drag during running.
A measure of the speed and direction of the air that is colliding with your body.
There are two approaches to reducing relative velocity.
(1) run on days when there is little or no wind
(2) use a movement technique called "drafting"
-following runner experiences smaller drag forces = energy efficiency
Vertical Ground Reaction Force
There are 2 methods for reducing the magnitude of the vertical ground reaction force on the slowing down side of the model.
(1) create a smaller body component mass
- -short term: wearing the lightest clothing and shoes possible
- -long term: changing body composition/loss of fat mass
(2) increase the application time of the vertical ground reaction force when the body collides with the ground
Coefficient of Friction
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 is not an option because it 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.
Application Time of Each External Force
The most effective method to decrease the application time of the friction force is to land with your foot underneath your center of mass.
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 joint should be slightly plantar flexed prior to contact with the ground and then upon contact with the ground, the ankle plantar flexor muscles should be contracted to create an eccentric ankle dorsiflexion torque
(3) the knee joint should be slightly flexed prior to contact with the ground
(4) the hip joint should be slightly flexed prior to contact with the ground
for the drag force, there is nothing that can be done to reduce the application time
Theoretically, increasing the mass would be an effective method to reduce how much you slow down. Unfortunately, a larger mass is more difficult to move quickly.
There is a mass concept box on the speeding up side of the model; and the interpretation for that box was that the mass must be small if we want to effectively speed the body up. These two interpretations conflict.
However, the logic should be easy to see. We need to get the body moving quickly each time we propel ourselves forward. This requires the mass be as small as we can make it. There is no way to simultaneously increase the mass so that we don't slow down as much.
This concept should not be taken literally. it does not mean run a shorter distance.
Instead, its meaning is that if you are planning to run for a 5K race, then only run 5000 meters. Do not run 5001, 5010, or 5020 meters. How is this accomplished?
There are 2 specific rules:
(1) when the road or path is curved, run close to the curve
(2) run in a straight line from curve to curve