Qualitatively different modes of manual lifting

Abstract The question of whether qualitatively different modes of manual lifting exist is addressed via an ideographic analysis of data from an experiment in which 39 subjects lifted loads of varying mass. Angular motion in the sagittal plane of ankle, knee, hip, and lumbar vertebral joints was estimated from video images collected while each subject performed 100 lifts. Bimodality in the frequency distribution of postures adopted at the start of lifting was evident in the data from 4 subjects. While semi-squat postures were usually adopted at the start of lifting, on some trials a stooped posture was observed. The likelihood of a stooped posture being adopted at the start of lifting was related to load mass. Both postures were observed when the load mass was relatively light, while only the semi-squat posture was observed when the load mass was increased. Subjects who adopted stooped postures on some or all trials were also, on average, taller, heavier, and stronger. Relevance to industry The observation of qualitatively different modes of lifting, and the influence of task characteristics on the techniques adopted, has implications for manual handling training.