Analysis of Manual Work

1. Analysis of Manual Work • Objectives • Review traditional job analysis methods • Introduce ergonomic job analysis methods for identifying potential for worker exposure to physical ergonomic stressors • Examine specialized tools for assessing risk associated with manual materials handling work • special focus on revised NIOSH Lifting Equation • Review general recommendations for manual materials handling work

2. Review traditional job analysis methods Describing Manual Work • Why would methods for describing manual work be useful?

3. Review traditional job analysis methods Job AnalysisTraditional IE methods • Tools and procedures for describing certain aspects of a job • Taylor and the Gilbreths were pioneers • Methods: • Descriptive methods • ex: operation process charts, flow process charts • Predictive methods • ex: MTM, MOST - repetitive tasks • Assessment methods • ex: work sampling, time study

4. Review traditional job analysis methods Benefits of traditional analysis methods... • Description of manual work

5. Ergonomic job analysis Ergonomic Job Analysis* • A method for identifying and evaluating generic risk factors associated with work-related musculoskeletal disorders • Based on collection of data about a job, designed to address these questions: • 1) Does performing the job expose a worker to any generic ergonomic risk factors? • 2) What aspects of the job cause or contribute to worker exposure? *Keyserling et al. (1991)

6. Ergonomic job analysis Generic Ergonomic Risk Factors • Characterized by excesses in Intensity, Duration, and/or Frequency: • Force exertion • Posture • Contact stress • Dynamics • Vibration • Temperature

7. Methods Tasks Tools and Equipment Workers Work Organization Environment Ergonomic job analysis Aspects of a job that may result in exposure to generic ergonomic risk factors

8. Ergonomic job analysis Elements of Ergonomic Job Analysis • Preparation • team • equipment • Method • Adverse health outcomes assessment • Basic job documentation • Identification of risk factor exposures • Evaluation of risk factor exposures • Exposure control

9. Ergonomic job analysis Method - Adverse health outcomes assessment • Data sources:

10. Ergonomic job analysis Method - Basic Job Documentation • Job analysis team members and date • Uniquely identify job • Describe worker(s) • Describe work objectives • Work schedule • Production &/or work pace info • Describe job rotation • Sketch work station layout • List tools and equipment • List all handled parts and materials • Describe work methods

11. Ergonomic job analysis Method - Identification of risk factor exposures • Determine risk factors associated with each work element • risk factor checklist can be useful, but familiarity with job is essential • Determine risk factor exposure for total job >>>>>>>>> Generic risk factors <<<<<<<< Work element Description Force Posture Contact stress…… A Thread wire through Y (based Y (pinch grip) Y (wire into fingertip) hole in insulator on gage) B…………..

12. Ergonomic job analysis Method - Evaluation of risk factor exposures • Bases for evaluation of risk: • epidemiological data • company data • specialized tools • examples: • Lifting: NIOSH lifting equation, Michigan model, LMM, ... • Posture: RULA, OWAS, … • distal upper extremity: Strain Index (combines posture, force, etc) • After identification and evaluation, summarize findings

13. Ergonomic job analysis Method - Exposure control • Develop alternative solutions • Perform follow-up ergonomic job analysis to evaluate controls

14. Use of specialized tools in analysis of MMH tasks Analysis of Manual Materials Handling Tasks • Importance of MMH tasks relative to workplace MSDs • 1994 workplace stats: 529,741 injuries due to overexertion in lifting, pushing or pulling, holding, carrying or turning objects • low back region is the primary area of injury

15. Use of specialized tools in analysis of MMH tasks Injury Prevention Strategies • Task design • Worker selection • Worker training

16. Use of specialized tools in analysis of MMH tasks MMH Risk Factors Associated with Low Back Disorder/Low Back Pain* • Lifting and force movements • Heavy physical work • Awkward postures • Whole body vibration (in conjunction with lifting and awkward postures) • Static work postures * NIOSH, 1997

17. Use of specialized tools in analysis of MMH tasks MMH System • In analyzing a MMH task, consider the system characteristics…. • worker • material - container • task - workplace • work practices …and which characteristics might give rise to the risk factors mentioned previously

18. Use of specialized tools in analysis of MMH tasks Establishing Lifting Limits - Revised NIOSH Equation • Bases: • Epidemiology: • injury rates for workers on jobs with LI>3 are quite high • Biomechanics: • 3400 N of disc compression • Physiology: • 2.2-4.7 kcal/min (task dependent) • Psychophysics: • acceptable to 75% of females, and 99% of males.

19. Use of specialized tools in analysis of MMH tasks Form of the NIOSH Equation Recommended weight limit (RWL) = LC * (HM * VM * DM * AM * FM * CM) where: LC: recommended maximum load, under optimal conditions and, all other factors are discounts to that maximum, to account for less-than-optimal conditions HM: accounts for horizontal distance from spine - as distance increases, RWL decreases VM: accounts for vertical height of start or end of lift - penalized if start or end varies from 75 cm, (about table/knuckle height) DM: accounts for vertical travel distance of load - penalized if distance exceeds 25 cm AM: accounts for lifting outside of the sagittal plane - penalized as move further away from sagittal CM: accounts for hand-handle coupling - poorer coupling results in reduction of RWL FM: accounts for rate of lifting - as rate increases, RWL decreases

20. Use of specialized tools in analysis of MMH tasks Revised NIOSH EquationAssumptions and Limitations • Assumptions: • smooth lifting (no acceleration) • moderate sized object • unrestricted lifting postures • two-handed, various hand-load coupling • steady lifting while standing • favorable temperature • main job is MMH, others require little energy • good traction for feet, no foot movement • same risk for lifting and lowering • Limitations: • Individual risk is not assessed (protective at the group level)

21. Use of specialized tools in analysis of MMH tasks Pushing and Pulling in MMH • Dangers: • overexertion • slipping • Important factors: • friction • shoe/floor • wheels • handle height • foot location

22. Use of specialized tools in analysis of MMH tasks Asymmetric Loading in MMH • Recommendation: • two-handed symmetric lifts • But asymmetry is more common: • one-handed handling • twisting or lateral bending of trunk • Problems with asymmetry: • capability decreases as: • stability decreases • greater reliance on one muscle instead of right-left pair

23. Use of specialized tools in analysis of MMH tasks Additional analysis tools for more complex MMH tasks • Shoaf et al equation - determines maximum predicted load for condition • accounts for push, pull, carry, lift • accounts for personal factors • Michigan model - determines % capable at every joint (determines weak link) • considers individual anthropometry • accounts for various postures throughout kinematic chain • Lumbar Motion Monitor model - determines LBD risk associated with task • considers trunk dynamics and moment of hand load

24. General recommendations for MMH work MMH job design recommendations • Eliminate MMH if possible • If not possible, then implement administrative or engineering controls • Administrative controls: • Engineering controls: