Handle positions and angles in a dynamic lifting task Part 1. Biomechanical considerations

Abstract

This first part of a two-part paper describes the biomechanical (body and box angle) measurements taken during a study of manual lifting and lowering of cubic boxes. Fifteen male and fifteen female manual materials-handling workers lifted and lowered boxes with all combinations of two handle angles to the horizontal (35° and 70°) and four handle positions (three asymmetric and one symmetric) through three lifting (lowering) distances (floor-waist, waist-shoulder, floor-shoulder; reversed for lowering). Angles were measured at each of five stages of lift or lower between floor and shoulder heights. The main accommodation of the subject to the changing demands of the task was to let the handle ‘slip’ with respect to the hand so that the handle was mainly gripped with either the first or fourth digits. This ‘slippage angle’ could be minimized with a 70° angle between handle and box horizontal and by choosing an asymmetric handle position with one hand in the centre of the lower edge and the other in the centre of the front edge of the box. A box design incorporating hand-hold cut-outs with these features is proposed.