Affiliations: [a] Biodynamics Laboratory, The Ohio State University, Columbus, Ohio, USA | [b] Low Back Biomechanics and Workplace Stress Laboratory, Department of Environmental Health, University of Cincinnati Medical College, Cincinnati, Ohio, USA | [c] Department of Environment, Health & Safety, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
Correspondence:
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Corresponding author: Kermit G. Davis, Department of Environmental Health, University of Cincinnati, 3223 Eden Ave, Cincinnati, Ohio 45267-0056, USA. Tel.: +1 513 558 2809; Fax: +1 513 558 4397; E-mail: kermit.davis@uc.edu
Abstract: Although there have been numerous studies evaluating the difference between stooped and squat lifting styles, there remains a lack of understanding of whole body kinematics during unrestricted lifting. The current study evaluated nine males and nine females while lifting two box weights (9.1 kg, 18.2 kg) from five origins below the waist (0, 19, 38, 57, and 76 cm above the floor) and from three task asymmetries (sagittally symmetric, 45° clockwise, 45° counter-clockwise). While the lifting style was significantly influenced by the height of lift origin and to a lesser extent gender, box weight, and task asymmetry, none of the conditions resulted in pure squat or stoop lifting style. However, for lifts above knee height, the lifting style resembled more of a stoop lift while lifts originating below knee height were more of a squat lift. As the origin moved closer to the floor, participants relied more on their hips to accomplish the sagittal flexion but overall adopted a more coordinated whole-body lifting style. All together, as more sagittal flexion is required, more joints are relied upon in a more coordinated effort. The current study indicates that caution needs to be exercised when applying results of pure squat or pure stoop lifting studies to free-style (realistic) lifting.
Keywords: lifting style, biomechanics, manual material handling, coordination, low back
