1. Biomechanics of Lifting Graduate Biomechanics

2. Biomechanics of Lifting Topics Lifting and Back Injury Biomechanics of Joint Torque and Shear Standards for Evaluating Lifting Tasks Biomechanical Factors Determining Joint Stress NIOSH and Evaluation of Lifting Risk

3. Lifting Varied Forms and Purposes Component of ADL’s Occupational Task Training for Strength Enhancement Competitive Sport

4. Lifting - Forms of Lifting Up Lifting Down Pushing Pulling Supporting Rising to Stand Sitting Bending

5. Lifting Injury Why so much interest in lifting ??

6. Lifting Workplace Injury Incidence of Lifting-related Injury 2% of workers yearly 21% of all workplace injuries 33% of workplace health care cost

7. Lifting-Related Injury Economic Impact *** Billions ***

8. Common Sites for Lifting Related Injury Incidence Rates: (i.e. frequency of injury) #1 Low Back #2 Wrist and Hand #3 Upper Back #4 Shoulder #5 Knee #6 Elbow

9. Low Back Pain Second leading cause of physician visits Third ranking cause of surgery (250,000 + yearly) Fifth ranking cause of hospitalization 15% of adults experience episode each year Lifting-related Injury is the Leading Cause of Low Back Pain !

10. Lifting Roles of the Clinician ** Treatment ** What Can be Done ? ** Prevention **

11. Lifting Injury Prevention ** Many Issues **

12. Potential Areas Influencing Risk The Lifter The Load The Task The Conditions

13. The Lifter Factors Influencing Risk Anthropometrics Strength Endurance Range of Motion Technique Sensory Health Status

14. The Load Factors Influencing Risk Weight Size and Shape Load Distribution Grip Coupling

15. The Task Factors Influencing Risk Complexity Workplace Geometry Frequency Duration

16. Conditions Factors Influencing Risk The Workplace Environment

17. Lifting Technique- Common Elements What do all forms of Lifting Have in Common ?? Imposed Loads Motion - Inertia Joint Torques Joint Compression Joint Shear

18. Biomechanics of Joint Motion The Biomechanical Model External Torque The External Torque and intended direction of motion determine the Internal Torque Internal Torque If External Torque > Internal Torque… Trunk Flexion If Internal Torque > External Torque… Trunk Extension If External Torque = Internal Torque… Equilibrium

19. Biomechanics of Joint Motion The Biomechanical Model Load - magnitude Position of Load Upper Body Mass Position of Upper Body Inertia External Torque The External Torque is Determined by:

20. Biomechanics of Joint Motion The Biomechanical Model The External Torque is Determined by: COG Axis Line of Gravity Moment Arm Torque = (Total Load) * (cosine of Slope * Moment Arm) Total Load = Mass of HAT + External Load

21. Biomechanics of Joint Motion The Biomechanical Model The External Torque is Determined by: COG Axis Line of Gravity Moment Arm Torque = (Total Load) * (cosine of Slope * Moment Arm) Body Mass = 150 # HAT = 60 % of BM Load = 50 # Trunk Angle = 60 deg Moment Arm = 1.2’

22. Biomechanics of Joint Torque External Torque Body Mass = 150# Load = 50# HAT = 60% of Body Mass COG Distance = 1.2’ Trunk Slope = 60 deg Torque = (Total Load) * (cosine of Slope * Moment Arm) Torque = (90# + 50# ) * (.5 * 1.2’ ) External Torque = 84 ft/lbs External Torque

23. Biomechanics of Joint Torque External Torque External Torque = 84 ft/lbs External Torque How Much Internal Torque is Needed to produce Equilibrium ?? 84 ft/lbs

24. Biomechanics of Joint Torque External Torque External Torque How Much Internal Torque is Needed to produce Equilibrium ?? 84 ft-lbs How hard do the extensor muscle have to work to produce the needed internal torque ???? Muscle Moment Arm =.15’ Internal Torque

25. Biomechanics of Joint Torque External Torque External Torque How Much Internal Torque is Needed to produce Equilibrium ?? 84 ft-lbs Internal Torque = MMA * Muscle Force 84 ft-lbs =.15’ * Muscle Force Muscle Force = 84 ft-lbs /.15’ Muscle Force = 560 lbs Muscle Moment Arm =.15’ Internal Torque

26. Biomechanics of Joint Torque Joint Compression Body Mass = 150# Load = 50# HAT = 60% of Body Mass Moment Arm = 1.2’ Trunk Slope = 60 deg Muscle Moment Arm=.15’ Joint Compression = HAT + Load + Muscle Contraction Joint Compression = 90# + 50# + 560# Joint Compression = 700# Joint Compression How about Joint Compression ??

27. Biomechanics of Joint Torque Joint Compression Additional Factors Motion – speed of lift Rotation – Transverse Plane

28. Lifting Technique COG What can be done to decrease low back stress ? (1)Lighten the Load

29. Lifting Technique COG What can be done to decrease low back stress ? (1)Lighten the Load (2)Change the position of the Load

30. Lifting Technique COG What can be done to decrease low back stress ? (1)Lighten the Load (2)Change the position of the Load (3)Change the position of the Body

31. Lifting Technique Torque BadGood COG

32. NIOSH National Institute for Occupational Safety and Health * Work Practices Guide to Manual Lifting, 1981

33. NIOSH What do they do ?? Define risk associated with lifting Define “safe” lifting conditions Publish lifting guidelines and standards for the workplace Inspect workplace for safe lifting conditions Impose penalties for hazardous lifting conditions

34. NIOSH - Hazardous Lifting Dependent on: Weight of Object Location of Object COM at beginning of lift Vertical travel distance of object Frequency of Lift (lifts per minute) Duration of lifting

35. NIOSH Standards Action Limit and Maximum Permissable Limit AL: Tolerated by 99% of males and 75% of females L5/S1 compression below 3400N Energy cost below 3.5 kcals/min **If any exceeded - some risk of injury MPL: Tolerated by 25% of males and 1% of females L5/S1 compression above 6500N Energy cost above 5 kcals/min **If exceeded severe risk of injury

36. NIOSH Standards Below AL - Stress tolerated by most workers Above AL and below MPL - Risk of injury such that task re-design or change in worker may be necessary Above MPL - Unacceptable risk...Must re- design task