Responses to manual handling training and repetitive lifting: changes in spinal compression and shear forces

Abstract: Manual handling (MH) is a leading cause of work-related ill-health, resulting in substantial personal and financial costs. Despite the lack of evidence to support the benefits of MH training, this remains an intervention strategy for many workplaces. Understanding reasons why MH training may be ineffective needs to be understood if work-related musculoskeletal disorders (MSD) are to be addressed. The aim of this study was to investigate the effects of prior MH training on spinal loading over the course of a repetitive handling task. Twelve male adults (mean age = 30 yr; mean body weight = 70 Kg) considered novices in repetitive MH, participated in the study. Participants attended two sessions during which they repetitively lifted (10 lifts/min) and lowered a box (13 kg) for up to 20 mins. No instructions about lifting technique were provided prior to session 1, whereas session 2 was preceded by training in recommended 'safe lifting'. Three-dimensional (3D) motion analysis and ground reaction forces provided input into a musculoskeletal model (AnyBody Technology, Denmark), used to estimate spinal loading (L5/S1 compression and shear forces). A repeated measure ANOVA (3*2) was used to determine the main effects of time (0, 10 and 20 min) and training (self-selected vs MH training) on spinal loading. A significant main effect was found for MH training on peak compression and shear forces (p=0.028 and p=0.024, respectively) when lifting, with higher peak forces in session 2 following the MH training session compared to session 1, a self-selected technique (3.29 KN vs 3.14 KN and 1.93KN vs 1.84 KN, respectively). Repetitive lifting led to decreases in cumulative compression and shear forces and increases in the slope of these curves (rate of change of loading) over time when lifting. MH training targeting ‘safe lifting’ appears to increase the risk of back injury and may discourage some individuals from adopting recommended handling practices. MH training should consider the wider context of work, challenge individuals to be adaptative to work situations, be job and task-specific, and be based on a sound andragogical rationale.

Keywords: Manual Handling, Musculoskeletal Disorders, Manual Handling Training, Repetitive Lifting, Spinal Compression Forces, Spinal Shear Forces

DOI: 10.54941/ahfe1006987

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