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Acceptable weights and physiological costs of performing combined manual handling tasks in restricted postures.
Ergonomics 1991 Jul; 34(7):939-952
Eight healthy, male underground coal miners (mean age = 36.9 +/- 4.5 Sd) participated in a U.S. Bureau of Mines study examining psychophysically acceptable weights and physiological costs of performing combined lifting and lowering tasks in restricted headroom conditions. Independent variables included posture (stooping or kneeling on two knees), task symmetry (symmetric or asymmetric), and vertical lift distance (35 or 60 cm). All tasks were 10 min in duration and were performed under a 1.22-M ceiling to restrict the subject's posture. Subjects were required to raise and lower a lifting box every 10 s and asked to adjust the box weight to the maximum amount they could handle without undue strain or fatigue. During the final 5 min of each test, data were collected to determine the energy expenditure requirements of the task. Results of this study demonstrated that psychophysical lifting capacity averaged 11.3 pct lower when kneeling as compared to stooping. Subjects selected 3.5 pct more weight in asymmetric tasks, and lifted 5.0 pct less weight to the 60-cm shelf compared to the 35-cm shelf. Materials that must be lifted manually in low-seam coal mines should be designed in accordance with the decreased lifting capacity exhibited in the kneeling posture.
Coal-mining; Coal-miners; Psychophysiological-testing; Posture; Manual-materials-handling; Manual-lifting; Musculoskeletal-system; Muscle-stress; Muscle-physiology; Muscle-function
OP; Journal Article
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Page last reviewed: May 5, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division