Ergonomic evaluation of standard and alternative pallet jack handless |
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| Affiliation: | 1. Department of Occupational & Environmental Medicine, University of California at San Francisco, San Francisco, CA, USA;2. Department of Physical Therapy, Samuel Merritt University, Oakland, CA, USA;3. Liberty Mutual Research Institute for Safety, Hopkinton, MA, USA;4. Safety and Health Assessment and Research for Prevention (SHARP) Program, Washington State Department of Labor and Industries, Olympia, WA, USA;1. Australian Research Centre for Human Evolution, Griffith University, 170 Kessels Road, Nathan, QLD 4111, Australia;2. Human Evolution Research Institute, University of Cape Town, Rondebosch, N Cape Town 7700, South Africa;3. Forensics and Archaeology, School of Environment and Science, Griffith University, 170 Kessels Road, Nathan, QLD 4111, Australia;1. Faculté des sciences de l׳activité physique, Université de Sherbrooke, Sherbrooke, Québec, Canada;2. Institut de recherche Robert Sauvé en santé et en sécurité du travail, Montréal, Québec, Canada;1. Chalmers University of Technology, Department of Technology Management and Economics, Division of Supply and Operations Management, Vera Sandbergs Allé 8, Göteborg, SE 41296, Sweden;2. Chalmers University of Technology, Department of Industrial and Materials Science, Division of Production Systems, Hörsalsvägen 7A, Göteborg, SE-412 96, Sweden;3. Volvo Group Trucks Operations, Norra Stenebyvägen 5, Göteborg, SE-405 08, Sweden |
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| Abstract: | AimTransportation of materials using a pallet jack pulled behind the operator is common due to the visual advantages while transporting fully loaded pallets. The objective of this laboratory study was to quantify muscle activity, posture, and low back compressive and shear forces while completing typical pallet jack activities using a standard handle that required one handed pulling of a pallet jack compared to an alternative handle that allowed for two handed pushing.MethodsParticipants (n = 14) performed six to ten trials of common pallet jack tasks (straight travel and turning) with each handle. Posture analysis of the trunk and right upper extremity was performed using Motion Analysis (Santa Rosa, CA, USA) and back compressive and shear forces were analyzed using 3D Static Strength Prediction Program (University of Michigan, Ann Arbor, MI). Activity of the upper trapezius (UT), pectoralis major (PM), flexor digitorum superficialis (FDS) and extensor digitorum (ED) muscles were recorded (Telemyo 2400 T, Noraxon, Scottsdale, Arizona) and normalized to percent reference voluntary contraction values. All outcomes were compared using the paired t-test.ResultsPeak and mean muscle activity of the PM (p < 0.001) and ED (p < 0.01) were significantly higher using the alternative push handle during all three tasks. There were larger compressive forces at L4/L5 (p < 0.08) and L5/S1 (p < 0.002) using the alternative handle, and greater shear forces using the standard handle at both L4/L5 (p < 0.0001) and L5/S1 (p < 0.000).DiscussionThe standard handle outperformed the alternative handle with regard to muscle activity. The alternative handle had significantly greater compressive forces at L5/S1 due to the pushing nature of the hand-handle interface, yet the standard handle increased shear forces at both L4/L5 and L5/S1 levels in the low back.ConclusionIn this analysis, there was not a clear benefit to using either handle in terms of trunk strength capacity and varied benefits and drawbacks to each handle when comparing compressive and shear forces in the low back. However, given favorable subjective reports described in a prior publication, and the increased reliance on dynamic versus passive force production, facilitating a workers' ability to push a pallet jack while travelling with large loads is worth further investigation. |
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| Keywords: | Push Pull Pallet jack Manual material handling |
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