Slide 1Slide 2Intermittent Work (Work/Rest Cycles)Task/Work AnalysisAcceptable Job Energy ExpenditureSlide 6ENERGY COST OF WORKHeart RateMonitoring Fatigue Heart Rate RecoverySubjective ratings of perceived exertion (RPE) (Borg, 1960)Ratings for WorkWork EfficiencyIE 5531IE 553 Engineering of Human WorkDr. Andris FreivaldsClass #27IE 5532IE 553 Engineering of Human WorkDr. Andris FreivaldsClass #27IE 5533Intermittent 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 state412 WIE 5534Task/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]/TwIE 5535Acceptable Job Energy Expenditure•Recommended physical work capacity•ERPWC = VO2max/3 • uniform work best•excursions worse•static worse than dynamic•large muscles better than localized loadingAgeRPWCTimeIE 5536Acceptable Job Energy Expenditure•For jobs exceeding RPWC:–Rest allocation or work/rest cycling–Tr = T(Ew - ERPWC) (Ew - Er)IE 5537ENERGY COST OF WORKIE 5538Heart Rate •HR proportional to energy expenditure•∆HR = working HR – resting HR •∆HR (Work pulse) ≤ 40IE 5539Monitoring 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 –HR1 – HR2 ≥ 20/min•Avoid heart rate creep•Short, frequent work-rest cyclesIE 55310 Subjective ratings of perceived exertion (RPE) (Borg, 1960)IE 55311Ratings for WorkRating (AIHA)Energy (kcal/min)Heart Rate (/min)BorgLight < 2.5 < 90 < 9Moderate < 5.0 < 110 < 11Heavy < 7.5 < 130 < 13Very heavy < 10 < 150 < 15Extreme > 10 > 150 > 15IE 55312Work Efficiency•Gross efficiency (%) = WorkOut/E × 100•Net eff. (%) = WorkOut/(E-BMR) ×
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