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Maximum acceptable weights and maximum voluntary isometric strengths for asymmetric lfting.
Ergonomics 1986 Jul; 29(7):879-892
The maximum acceptable weights and maximum voluntary isometric strengths for two handed asymmetric lifting were studied. Thirteen healthy young male volunteers with a mean age of 26.2 years and a mean body weight of 80.6 kilograms participated in the study. Subjects were required to lift loaded boxes of three different sizes, 51 x 25 x 25, 51 x 38 x 25, and 51 x 51 x 25 centimeters (cm), from the floor to a height of 81cm at four body positions, namely zero, 30, 60, and 90 degrees from the sagittal plane. The weights were adjusted by the subjects to the maximum amount they could comfortably lift at a rate once every 5 minutes. The subjects chose stoop, squat, and semistoop lifting techniques according to their preferences. The mean maximum acceptable weight for small size boxes at the sagittal plane was 472, for medium size boxes it was 413, and for large boxes it was 367 Newtons (N). At the 30 degree angle from the sagittal plane, the values decreased to 364, 328, and 282N, respectively. The mean maximum voluntary isometric strength (MVIS) at the sagittal plane for the three size boxes was 513, 437, and 355N, respectively. The MVIS decreased at 90 degrees asymmetric lifting to the mean lift values of 363, 303, and 249N, respectively. The strength values for the 30 and 60 degree angles were between the values for zero and 90 degree planes. The authors state that both the maximum acceptable weight and static strength for asymmetric lifting are lower than in symmetric sagittal plane lifting. Therefore, correction factors of 7, 15, and 22 percent for maximum acceptable weight and 12, 21, and 31 percent for static strength at 30, 60, and 90 degrees of asymmetric lifting are recommended to modify existing data on the symmetric sagittal plane lifting.
NIOSH-Author; Humans; Men; Ergonomics; Work-practices; Task-performance; Job-analysis; Muscle-stress; Physical-fitness
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Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division