Affiliations: [a] Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hong Kong | [b] Department of Mathematical Sciences, University of Cincinnati, Cincinnati, OH, USA | [c] Industrial & Manufacturing Engineering Program, University of Cincinnati, Cincinnati, OH, USA | [d] Center for Industrial Ergonomics, University of Louisville, Louisville, KY, USA | [e] Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong
Correspondence:
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Address for correspondence: Simon S. Yeung, Department of Rehabilitation Sciences, The Hong Kong Polytechnic University, Hung Hom, Hong Kong. Fax: +852 2330 8656; E-mail: simon.yeung@polyu.edu.hk
Abstract: The Revised NIOSH Lifting Equation [13] integrated the findings of different approaches reported in the scientific literature into a single mathematical formulation based on the empirical model proposed by Drury and Pfeil [5]. This simple model was tested on a limited basis and the model generalizations have not been examined. The primary objectives of this study were to investigate the performance of the NIOSH lifting equation with general formulations reported by Karwowski [7], and to examine the structure of the lifting index and the relative importance of physical factors (as defined by the lifting index) and non-physical factors (as defined by perceived risk of injury and work dissatisfaction) with respect to workers' perceived effort associated with the lifting conditions. A cross-sectional study was conducted on 217 experienced manual handling workers in the Hong Kong area to validate the study objectives. In this investigation, information was collected on lifting task parameters, perceived effort, perceived risk of injury, and work dissatisfaction. The results suggest that a multiplicative model is better than an additive model in evaluating the effort associated with lifting task performance. In this regard, the exponents of the parameters in the lifting index should be different from 1.0. The best model for evaluating effort emerged from perceived risk of injury and the general lifting index (GLI). Given the limitations of our observational study, the main findings from this research suggest that the multiplicative structure of the NIOSH lifting equation is better than an additive model. In addition, the weighing of lifting task multipliers may need further investigation, and the study of manual lifting tasks should include both physical and non-physical factors when examining the etiologic factors leading to musculoskeletal symptoms and disorders.
Keywords: Manual lifting, general lifting index, field study, task evaluations, worker-based assessment
