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IE 327 Introduction to Work Design Dr. Andris Freivalds Class #4

IE 327 Introduction to Work Design Dr. Andris Freivalds Class #4. Ch. 4 – MUSCULOSKELETAL SYSTEM (and Work Design). MUSCLE STRUCTURE. Muscle and tendon Bundle of fibers Blood vessels Muscle fiber Myofibril Thick filament = myosin Thin filament = actin Sliding filament theory.

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IE 327 Introduction to Work Design Dr. Andris Freivalds Class #4

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  1. IE 327 Introduction toWork Design Dr. Andris Freivalds Class #4 IE 327

  2. IE 327

  3. IE 327

  4. IE 327

  5. IE 327

  6. IE 327

  7. Ch. 4 – MUSCULOSKELETAL SYSTEM (and Work Design) IE 327

  8. MUSCLE STRUCTURE • Muscle and tendon • Bundle of fibers • Blood vessels • Muscle fiber • Myofibril • Thick filament = myosin • Thin filament = actin • Sliding filament theory IE 327

  9. FORCE-LENGTH RELATIONSHIP(Max strength at midrange) IE 327

  10. Achieve max muscle strength at midrange of motion • Where is midrange? • Relaxed posture • No muscle force • Weightless astronaut in space • Avoid extremes!! IE 327

  11. FORCE-VELOCITY RELATIONSHIP • Max muscle force with slow motion • Use momentum to assist work • Minimize fighting gravity IE 327

  12. OPTIMIZE HUMAN STRENGTH • Use optimum postures • Use large muscles for power • Avoid using back • Design tasks so that most can do! IE 327

  13. MUSCLE ENDURANCE • Static hold • Occlusion of blood flow • Rapid fatigue • Stay < 15% max • Short, frequent work-rest cycles • Dynamic work IE 327

  14. MOTOR UNIT RECRUITMENT • Use small muscles for precision • Use large muscles for power • Power vs. pinch grip!! IE 327

  15. CONTROL OF MOVEMENTS #1 • Pivot on elbow • Curved motions • Use both hands • Begin and end motion simultaneously • Move simultaneously to and from body • Use natural rhythms • Whole body = 17/min • Whole arm = 35/min • Forearm = 60/min IE 327

  16. CONTROL OF MOVEMENTS #2 • Use lowest classification of movement • Decrease difficulty of task • ↓ distance • ↑ target width IE 327

  17. MINIMIZE EYE MOTION(Within normal line of sight) IE 327

  18. KEY POINTS: • Design work according to human capabilities and limitations • For manipulative tasks: • Dynamic motion rather than static holds • Strength requirements < 15% max • Avoid extreme ranges of motion • Small muscles for speed and precision • Large muscles for strength IE 327

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