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Effect of Posture on Metabolic Expenditure Required to Lift a 50- Pound Box.
Ch in "Trends in Ergonomics/human Factors V" 1988 :927-934
This Bureau of Mines paper describes tests in which 11 healthy, underground coal miners (36 yr of age +- 8 sd) participated in an experiment examining the metabolic cost of lifting a 50-lb box asymmetrically in stooped and kneeling postures. Lifting periods were 10 minutes in duration and the frequency was 10 lifts/min. Dependent measures included heart rate, oxygen consumption, ventilation volume, respiratory exchange ratio, and integrated electromyography (emg) of eight trunk muscles. Results of an analysis of variance with repeated measures showed that heart rate (p < 0.05), Oxygen consumption (p < 0.001), Ventilation volume (p < 0.001), and respiratory exchange ratio (p < 0.05) Were all significantly elevated in the kneeling posture as opposed to stooped. A multivariate analysis of variance indicated that the maximum integrated emg of the trunk muscles was significantly different between the two postures (p < 0.05); Univariate f-tests demonstrated that the right and left erectores spinae were the muscles accounting for the significant multivariate effects, being substantially higher in the kneeling posture (p < 0.01). These results indicate that workers may be more susceptible to muscular fatigue when handling materials in the kneeling posture and that increased erectores spinae activity may cause higher compressive loads to be experienced by the spine when lifting in the kneeling posture. Results of this study suggest that decreasing the weight of loads handled in underground mines would be advisable, especially when lifting in the kneeling position.
Ch. in "Trends in Ergonomics/human Factors V" 1988, PP. 927-934
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Content source: National Institute for Occupational Safety and Health Education and Information Division