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IE 553 Engineering of Human Work Dr. Andris Freivalds Class #26

IE 553 Engineering of Human Work Dr. Andris Freivalds Class #26. IE 553 Engineering of Human Work Dr. Andris Freivalds Class #26. Anaerobic. Aerobic. Physical Work Capacity ( Å&R, Ch.7,8,11). Work Capacities (Demands) Aerobic (with oxygen)

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IE 553 Engineering of Human Work Dr. Andris Freivalds Class #26

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  1. IE 553 Engineering of Human Work Dr. Andris Freivalds Class #26 IE 553

  2. IE 553 Engineering of Human Work Dr. Andris Freivalds Class #26 IE 553

  3. Anaerobic Aerobic Physical Work Capacity (Å&R, Ch.7,8,11) Work Capacities (Demands) • Aerobic (with oxygen) • C6H12O6 + 6O2 ⇒ 6CO2 + 6H2O + 38ATP • Anaerobic (no oxygen) • C6H12O6 ⇒ 2C3H6O3 + 2ATP (Myoglobin) IE 553

  4. Intensity of Work • Submaximal tasks, as measured by: • VO2 • Lactate IE 553

  5. Energy Sources & Duration of Work IE 553

  6. Energy Sources & Duration of Work Myoglobin = quick, replenishable supplier of O2 IE 553

  7. Intermittent Work(Work/Rest Cycles) • Short, frequent W/R cycles are best • Self-paced work with spontaneous pauses • For prolonged work, VO2 should be at steady state 412 W IE 553

  8. Individual Differencesin Physical Work Capacity • Peaks at 25 then ↓ • Males > females • Due to body size IE 553

  9. Physical Fitness (Males 20-29, in ml/min/kg) Average = 3 l/min IE 553

  10. Measurement of Energy Expenditure • Direct calorimetry • Indirect calorimetry • Predict from oxygen uptake V02 (l/min)     = VE [I02 - EO2] VC02 (l/min)   = VE ECO2 E (kcal/min) = 3.94 V02 + 1.106 VC02 - 2.17 Neq      E (kcal/min)    = 3.9 V02 + 1.1 VC02      E (kcal/min)    = 4.9 V02 (if RQ = 0.9) RQ = VC02 / V02 IE 553

  11. Respiratory Quotient RQ = VC02 / V02 IE 553

  12. Measurement of Aerobic Capacity • Direct – supramax-imal task • Submaximal task, extrapolate with HR 1) Step levels of 5 min 2) Reproducible workload 3) Large muscle groups, 4) Not too much skill IE 553

  13. Task/Work Analysis • Basic requirements for a job/task: • Energy exp < VO2max • Fatigue threshold (?) • Repeatable task • Eave = (Ew×Tw + Er×Tr)/(Tw+Tr) • Ew = [Eave(Tw+Tr) - Er×Tr]/Tw IE 553

  14. ENERGY COST OF WORK IE 553

  15. Acceptable Job Energy Expenditure • Recommended physical work capacity: • ERPWC = VO2max/3             • uniform work best, • excursions make worse • static worse than dynamic • large muscles better than localized loading • For jobs exceeding RPWC: • Rest allocation or work/rest cycling • Tr = T(Ew - ERPWC) (Ew - Er) IE 553

  16. Monitoring Fatigue Heart Rate Recovery • Brouha guidelines • Measure HR at: • 0.5→1 min (HR1) • 2.5→3 min (HR2) • Acceptable work if: • HR1 < 110/min • HR2 - HR1 ≥ 20/min • Work pulse < 40 /min • Avoid heart rate creep • Short, frequent work-rest cycles IE 553

  17. Subjective ratings of perceived exertion (RPE) (Borg, 1960) IE 553

  18. Ratings for Work IE 553

  19. Work Efficiency • Gross efficiency (%) = WorkOut/E × 100 • Net eff. (%) = WorkOut/(E-BMR) × 100 • Ex. IE 553

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