Real-World: Jumping

To create a larger vertical ground reaction force, you must perform the vertical or horizontal jump on the hardest surface possible.

To create a larger coefficient of friction, the bottom surface of the shows that you are wearing must have 2 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

-a muscle with a larger physiological cross-sectional area will create more muscle force

-increase via resistance training

(2) Muscle Length

-muscles stretched to 120% of their natural resting length generate the most muscle force

(3) Speed of the Muscle Contraction

-muscles that are concentrically contracted at slower speeds generate greater force than muscles that are concentrically contracted at faster speeds

ANKLE PLANTAR FLEXION

• Fibularis Brevis/Longus
• Gastrocnemius
• Plantaris
• Soleus
• Tibialis Posterior

KNEE EXTENSION

• Gluteus Maximus
• Rectus Femoris
• TFL
• Vastus Lateralis/Intermedius/Medialis

HIP EXTENSION

• Adductor Magnus
• Gluteus Maximus/Medialis/Minimus
• Biceps Femoris
• Semimembranosus
• Semitendinosus

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. 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. When the long axes of the two bones connected at a joint are aligned long axis to long axis (straight line), the moment arm distance is the smallest.

SHORT-TERM

(1) wear the lightest clothing possible

(2) wear the lightest shoes possible

LONG-TERM

(1) lose fat mass

The distance from the joint's axis of rotation to the center of mass of the body component.

Individuals with shorter bones will have shorter radii of resistance. There is nothing we can do to decrease bone length.

We can change the radius of resistance by changing the angles of the joints within the body component being rotated. We can decrease the radius of resistance by rotating the body component closer to the joint axis of rotation.

To increase the application time of the concentric ankle plantar flexion joint torque:

DURING THE PREP PHASE

the ankle must be dorsiflexed

DURING THE EXECUTION PHASE

a concentric ankle plantar flexion joint torque is applied until the ankle is maximally plantar flexed

To increase the application time of the concentric knee extension joint torque:

DURING THE PREP PHASE

the knee must be flexed

DURING THE EXECUTION PHASE

a concentric knee extension joint torque is applied until the knee is maximally extended

To increase the application time of the concentric hip extension joint torque:

DURING THE PREP PHASE

the hip must be flexed

DURING THE EXECUTION PHASE

a concentric hip extension joint torque is applied until the hip is maximally extended

The distance from the joint's axis of rotation to the point of interest on the body component.

Individuals with longer bones will have longer radii of resistance. There is nothing we can do to increase bone length.

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.

To achieve a positive relative projection height for a horizontal jump, you would have to leave the ground with your center of gravity as high as possible and then land with your center of gravity as low as possible.

To achieve the optimal projection angle for maximum VERTICAL jump height, you would leave the ground with a projection angle of 90 degrees.

FOR HORIZONTAL JUMP:

If RPH = zero, leave the ground with a projection angle of 45 degrees

If RPH = POSITIVE, the jumper's projection angle should be LESS THAN 45 degrees

If RPH = NEGATIVE, the jumper's projection angle should be GREATER THAN 45 degrees