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EHS 218 Occupational Ergonomics

EHS 218 Occupational Ergonomics. Introduction to Quantitative Methods Anthropometry. Quantitative Methods. Most tasks can be analyzed using qualitative methods by following the basic principles of ergonomics Pick the right [ergonomic] tool for the right job

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EHS 218 Occupational Ergonomics

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  1. EHS 218 Occupational Ergonomics Introduction to Quantitative Methods Anthropometry

  2. Quantitative Methods • Most tasks can be analyzed using qualitative methods by following the basic principles of ergonomics • Pick the right [ergonomic] tool for the right job • The technique and approach must fit the needs and goals of the specific workplace • Good task analysis and problem solving can be achieved using simple checklists and worksheets

  3. When Quantitative Methods are Useful • Risk assessment • Numeric guidelines • Conducting “before and after” studies • Helping determine best alternatives • Matching jobs to employee restrictions • Evaluating appropriateness for job rotation • Conducting epidemiological studies • Documenting problems

  4. Objectives • To sharpen your ability to see problems and potential improvements • To learn about ergonomic methods • To understand when it may be useful to get additional help

  5. Ergonomic Measurements • Safety health, and well-being • Injury/illness rates • Workers’ compensation • Discomfort survey • Active medical surveillance

  6. Ergonomic Measurements • Human Resource • Satisfaction • Absenteeism • Turnover

  7. Ergonomic Measurements • Production • Errors • Output • Defects and other quality measures

  8. Ergonomic Measurements • Physical Task Requirements • Heights and reaches • Clearances • Force • Posture • Motions • Fatigue • Environmental

  9. Anthropometry

  10. Anthropometry Principles Associated with Anthropometry • Principle 3 – keep things in easy reach • Principle 4 – work at proper heights • Principle 8 – provide clearance

  11. Anthropometry The field of study that deals with the measurement of the human body Anthropos = human Metria = measurements

  12. Goals of Anthropometry • To make workplaces, equipment, and products fit the capacities for reach, heights, grasp, and clearance of the workforce or user population

  13. How Are We Different? • Dimensions vary considerably among humans • Secular Trends • Ethnic Trends • Weak correlation among individual body dimensions • “Average person” fallacy

  14. “Average Person” Fallacy

  15. “Average Person” Fallacy

  16. Useful Information Obtained through Anthropometry • Range of height adjustability to accommodate a given population • Maximum reach acceptable for small individuals • Minimum clearance acceptable for large individuals

  17. Factors Affecting Anthropometric Data • The task • Variations from elbow height; nature of work done affects the dimensions • Related tools and products • Dimensions of tools and products may affect choice of data

  18. Factors Affecting Anthropometric Data • Clothing • Such as hard hats, boots, heels, gloves, etc. • Workforce differences • Age • Gender • Ethnic background • General, industrial, or military populations

  19. Gender Differences

  20. Measurements • Based on a Normal Distribution of a population (Bell Curve) • Most people are in the center of the curve, with a few extremes at either end (smallest/weakest on the left and the largest/strongest on the right)

  21. Anthropometric Measurements • Types of data include: • Percentiles • Reach envelopes/limits • Clearance • Strength • Posture

  22. Mean (average) = 50th percentile Standard deviation = S.D. (degree of spread away from the mean) Percentiles

  23. Standard Deviation

  24. Reach Envelopes/Limits • Semicircles

  25. Clearance • Who needs to fit?

  26. Strength • How strong must we be to operate controls?

  27. Posture • Awkward postures result from poor designs

  28. What is Measured? • Whole body characteristics • Examples: Stature, body weight • Specific body landmarks • Examples: popliteus, biacromium

  29. What is Measured? • Body segment dimensions • Examples: shoulder/elbow length, tailbone/knee length • Functional dimensions • Examples: forward grip reach, forward reach

  30. What is Measured? • Common measurements used: • stature • forward reach • upward reach • sitting eye height • arm span • knee clearance • thigh clearance • shoulder breadth

  31. Rules of Thumb Let the small person reach and the large person fit!

  32. Rules of Thumb

  33. Rules of Thumb

  34. Design Approaches • Common design criteria • 5th to 95th (90% of population) or • +/- 2SD (95% of population) • Average individual - 50th percentile • Extreme individuals - 5th and 95th percentiles

  35. Design Approaches • Range of Adjustment - accommodate 5th to 95th percentile • Entire Population - If realistic • Clearance - design for the largest

  36. Design Approaches • Reach - design for the smallest • Strength - design for the minimum but not for accidental activation • Posture - design to minimize awkward and static postures

  37. Is Precision Necessary? • In most applications, the tabulated data can be rounded off • Never simply look up a dimension and use it blindly!

  38. The Anthropometric Process • Characterize the user population • Determine the percentile range to be accommodated in the design (let the small person reach and the large person fit) • Find the anthropometric measures that correspond to the workstation measures

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