Impact

Receiving a Force as a result of a Collision

Types of Impacts

    Impact from one's own Body
          Landing from a jump (vertical)
          Running into an object (horizontal)

    Impact from External Object
          Catching a Ball
          Blocked by another Player

Problems regarding Impact

    Impact from one's own Body

          Avoiding Injury
          Regaining Equilibrium Promptly

    Impact from an External Object

          Avoiding Injury
          Regaining Equilibrium Promptly
          Receiving the Object with Accuracy and Control

Relationships used with Impact Problems

    Kinetic Energy - Work Relationship

          Kinetic Energy Changes as Velocity Changes (KE = 1/2 mv2)
          Impact slows down the Object
                - decreases it's Velocity and Kinetic Energy
          Requires that Work is done on the Object (W = Fd)
                - or the Object does Work on the Body

          KEO - KEF = F(d)

                Energy -or- Work units (metric): (kg*m2)s-2

          Force and distance are, thus, directly related.

   Momentum - Impulse Relationship

          Momentum also changes as Velocity Changes (M = mv)
          Impact again slows down the Object
                - decreasing it's Velocity and Momentum
          Requires that a Force is applied for a given period of time
                - Impulse = Force * time

          MO - MF = F(t)

                Momentum -or- Impulse units (metric): (kg*m)s-1
          Force and time are, thus, directly related.

    Pressure - Force Relationship

             Large Pressures, NOT large Forces, increase the likelihood of Injury
             Pressure is Force per unit of Area

             P = N(m-2)

             Force and Area are, thus, Inversely related.


Applying these Concepts to Falls and Landings

      Avoiding Injury

             Is desirable to decrease Velocity gradually
                   - possible by:
                          increasing Distance through which Force is applied
                          increasing Time through which Force is applied
                          landing on "Giving" surfaces
                          controlled Flexion through Eccentric contractions
                          rolling after landing

             If working with limited ROM, then is sometimes appropriate to:
                   - increase the surface area that receives the impact

      Regaining Balance

             Balance is regained when Equilibrium is established
             Equilibrium is established when adequate Base of Support exists
             Therefore, regaining Balance is largely a problem
                   - controlling placement of the limbs before the landing

             * This improves as kinesthesis during the skill is achieved

Applying these Concepts to Catching

      Avoiding Injury

             Increase the Distance over which the Velocity decreases
                   - reach forward to allow for some additional motion
                   - flex intermediate joint (elbow) to decrease torque
             Use proper hand -or- foot positioning

      Maintaining Equilibrium

             Widen the Base of Support in the direction of the object
                   - also serves to increase the possible distance travelled

      Receiving with Accuracy or Control

             Make Proper Judgements on the Path and Velocity of the Object
             Requires: 
                   "Keeping an eye on the object"
             Accurate Judgement depends upon:
                   Accurate Vision
                   Accurate Adjustments of the Body
                          - Agility
                          - Smoothness of Neuromuscular Response
                   These make-up "hand-eye" -or- "foot-eye" coordination

             Intercepting a Pass

                   Catching allows for optimal (favorable) positioning of body
                   Intercepting does not
                   Therefore, intercepting also relies upon
                          - Agility
                          - Smoothness of Neuromuscular Response
                   But, also relies upon
                          - Reaction time
                          - Ability to "Give" with receiving part (hands/feet/stick)

             Receiving and Subsequent Movements

                   Often need to Run or Throw after Receiving Object
                   Need a Transition between skills
                   Is desirable to "blend" skills together (short-stop, etc)
                   Is dependant upon the degree of skill of the performer