1. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Chapter 22: Impact KINESIOLOGY Scientific Basis of Human Motion, 11 th edition Hamilton, Weimar & Luttgens Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University Revised by Hamilton & Weimar KINESIOLOGY Scientific Basis of Human Motion, 11 th edition Hamilton, Weimar & Luttgens Presentation Created by TK Koesterer, Ph.D., ATC Humboldt State University Revised by Hamilton & Weimar

2. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Objectives 1. Name common problems associated with the diverse forms of receiving impact. 2. Explain how the work-energy, impulse- momentum, and pressure-area relationships apply to receiving impact either of one’s own body or of external objects. 3. State the principles related to avoiding injury while receiving impact and furnish an application for each.

3. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Objectives 4. State the principles related to maintaining and regaining equilibrium while receiving impact and furnish an application for each. 5. State the principles related to accuracy & control while receiving impact & furnish an application for each.

4. © 2008 McGraw-Hill Higher Education. All Rights Reserved. MEANING OF IMPACT AND ITS RECEPTION Impact is derived from the Latin word impingere, “to press together”. Further defined as force of contact, violent collision, striking together. Receiving impact is opposing or resisting in some manner the force with which a moving body tends to maintain its speed and direction. Some impacts have a positive effect, such as stimulating bone development.

5. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Problems Problems in receiving impact: 1. Avoiding injury. 2. Maintaining equilibrium. 3. Receiving the object with accuracy and control.

6. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Concepts 1. Kinetic energy-work relationship: When a body or object is “received” it has work done on it equal in amount to the change in kinetic energy of the moving body.

7. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Concepts 2. Momentum-impulse relationship: Any change in momentum requires a force applied over a period of time (impulse) and is equal to the product of the force and the time.

8. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Concepts 3. Pressure-area relationship : The pressure that any part of the body must absorb is inversely proportional to the area over which the force is applied.

9. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Falls and Landings Important contributors to the gradual decrease in momentum without injury: Landing on “giving” surfaces; mats. Controlled flexion at the joints of the landing extremities through eccentric contraction of the antagonist muscles. Relationship of the force of impact to the size of the area that bears the brunt of the impact.

10. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Regaining Equilibrium Control the placement of the limbs in preparation for landing. Use control to place the feet, or hands and feet, in a position that will provide a favorable base of support. Adequate base of support needs to be established. Depends on the integrity of the bones and joints that receive the force of impact.

11. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Protective Equipment Used to dissipate the force of impact. Helmets: May be single impact (cycling) or multiple impact (football) design. Compression of interior foam increases both time and distance of force application, thus decreasing impulse and energy. Body protection: Serves same purpose as helmets. Often must also resist friction.

12. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Catching: Avoiding Injury Achieved by increasing the distance over which the object’s kinetic energy is lost. By moving the hands toward the body through a distance of 10 to 20 in. as a ball is received, the catcher is making it possible for the ball’s kinetic energy to be lost gradually. Hand position: Finger should be pointed either down or up, according to whether the ball is below or above the waist.

13. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Catching: Maintaining Equilibrium Widen the base of support in the direction of the ball’s flight. Allows weight shift from forward to rear foot at impact. Increases chances of maintaining equilibrium, and contributes to gradual reduction of ball’s motion.

14. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Catching: Accuracy and Control Accurate vision, judgement, and positioning of the body are of vital importance. “Keeping the eye on the ball”. Accurate judgement depends on accurate vision, and accurate adjustment of body position depends on both, as well as on agility and smoothness of neuromuscular response. “Hand-eye” & “foot-eye coordination”.

15. © 2008 McGraw-Hill Higher Education. All Rights Reserved. PRINCIPLES OF RECEIVING IMPACT Related to Avoiding Injury 1. The more gradual the loss of momentum (or kinetic energy) of the moving body or object, the less the force exerted on the body. Fig 22.1

16. © 2008 McGraw-Hill Higher Education. All Rights Reserved. PRINCIPLES OF RECEIVING IMPACT Fig 22.2Fig 22.3 Related to Avoiding Injury

17. © 2008 McGraw-Hill Higher Education. All Rights Reserved. PRINCIPLES OF RECEIVING IMPACT Related to Avoiding Injury 2. The larger the area receiving the impact, the less will be the force per unit of surface area. 3. Repeated impacts may lead to overuse injures. Attention should be given to the nature of the landing surface.

18. © 2008 McGraw-Hill Higher Education. All Rights Reserved. PRINCIPLES OF RECEIVING IMPACT Related to Maintaining and Regaining Equilibrium 4. Other things being equal, the larger the base of support in the direction of the impetus, the greater will be the body’s equilibrium. Fig 22.4

19. © 2008 McGraw-Hill Higher Education. All Rights Reserved. PRINCIPLES OF RECEIVING IMPACT Related to Maintaining and Regaining Equilibrium 5. At the moment of impact, the line of gravity should be lowered & centered above the base. Fig 22.5

20. © 2008 McGraw-Hill Higher Education. All Rights Reserved. PRINCIPLES OF RECEIVING IMPACT Related to Accuracy and Control 6. The more gradually the velocity of an external object is reduced, the less likely the object is to rebound when impact is received. 7. “Keep the eye on the ball” enables one to judge speed and direction and to respond accordingly.

21. © 2008 McGraw-Hill Higher Education. All Rights Reserved. PRINCIPLES OF RECEIVING IMPACT Related to Accuracy and Control Fig 22.6 8. Catching an external object with accuracy and control depends largely on the position of the catcher relative to the direction of the approaching object.

22. © 2008 McGraw-Hill Higher Education. All Rights Reserved. Chapter 22: Impact