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Handle positions and angles in a dynamic lifting task. Part 2. Psychophysical measures and heart rate.
Ergonomics 1986 Jun; 29(6):769-777
Psychological and physiological measurements were taken during a study of manual lifting and lowering of boxes employing a lifting task over three distances, floor to waist, waist to shoulder and floor to shoulder, and using boxes with hand hold cut outs in four handle positions (three asymmetric and one symmetric). Handle angles were fixed at either 70 degrees to the horizontal or 35 degrees. A group of 15 men and 15 women manual materials handling employees participated in the study. Sex factors were significant for physiological cost, perceived exertion and speed of lifting. Heart rate was generally higher in this dynamic task than in earlier static tasks, especially in lifts from floor level. During a 2 minute work period, heart rate almost reached a stable state. The mean at the fifth lift was 118.2 beats per minute while the mean at the seventh lift was 121.6 beats per minute. Body part discomfort was largely influenced by scores in the legs and thighs. These were much higher for lifts from floor level. Lifts from waist to shoulder showed the expected result that arm work was the chief source of pain and discomfort. The authors conclude that while the cost measures used in this paper support the biomechanical recommendations for handle angles, they neither support nor refute those recommendations for handle positions at any practical level. For general purpose manual materials handling, a box with hand hold cut outs enabling operators to use an asymmetrical hand position is recommended.
NIOSH-Author; Materials-handling-equipment; Biomechanics; Biomechanical-engineering; Musculoskeletal-system; Cardiovascular-system; Ergonomics; Human-factors-engineering
Issue of Publication
Musculoskeletal Disorders of the Upper Extremities; Disease and Injury; Musculoskeletal-system
Page last reviewed: March 11, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division