1. 1 Basic Biomechanical Factors and Concepts Anatomy and Physiology of Human Movement 420:050

2. 2 Outline Levers Anatomical Levers

3. 3 Outline Levers Anatomical Levers

4. 4 Introduction to Levers Lever: Simple machine that operates according to principle of torques Torque: The turning effect of a force T = Fd

5. 5 F d How can you change torque? 1. Change F 2. Change d 3. Change direction of F

6. 6 F d Optimal direction = 90 degrees

7. 7 Function of Levers Two functions: 1. Force 2. Speed/ROM

8. 8 Function of Levers Force Examples? Common traits? Rigid bar Fixed point Lever movement vs. resistance movement

9. 9 F R

10. 10 Function of Levers Speed/ROM Examples? Common traits? Rigid bar Fixed point Lever movement vs. resistance movement

11. 11 F R

12. 12 Components of a Lever System Lever: Rigid bar Fulcrum: Axis of rotation/fixed point Force: Applied force (F) Resistance force (R) Moment arm: d Applied force Resistance

13. 13 More Concepts Mechanical advantage Levers designed for force Mechanical disadvantage Levers designed for speed/ROM

14. 14 FR Mechanical advantage or disadvantage? How does mechanical advantage affect movement of the lever?

15. 15 Advantage: Small effort moves big resistance Disadvantage: Big movement required to move resistance a small distance

16. 16 Human Application? Lever? Bones (Not always a bar) Fulcrum? Joints Applied force? Muscles Resistance force? Weight of limb, external resistance

17. 17 Classification of Levers Lever classification based on the relative location of: 1. Axis of rotation/fulcrum (A) 2. Resistance force (R) 3. Applied force (F) A R F

18. 18 First Class Lever Center: (A) – Axis of rotation/fulcrum Mechanical advantage Mechanical disadvantage Examples Crow bar Seesaw

19. 19 Advantage or disadvantage?

20. 20 Second Class Lever Center: (R) – Resistance force Mechanical advantage Always Mechanical disadvantage Never Examples Wheelbarrow Nutcracker

21. 21

22. 22 Third Class Lever Center: (F) – Applied force Mechanical advantage Never Mechanical disadvantage Always Examples Rowing Shoveling Bat, tennis racket

23. 23 Baseball, tennis?

24. 24 Human Application First class lever Elbow extension against a resistance

25. 25 (A) – Axis of rotation/fulcrum (F) – Applied force (R) – Resistance force Mechanical advantage or disadvantage

26. 26 Human Application Second class lever Ankle plantar flexion

27. 27 Mechanical advantage or disadvantage? Not many in the body

28. 28 Human Application Third class lever Elbow flexion

29. 29 Mechanical advantage or disadvantage? Many of these in body

30. 30 In general, is the human body built for force application or speed/ROM?