Identification of potential biomechanical risk factors for low back disorders during repetitive rebar lifting

Purpose: Work-related low back disorders (LBDs) are prevalent among rebar workers although their causes remain uncertain. The purpose of this study is to examine the self-reported discomfort and spinal biomechanics (muscle activity and spinal kinematics) experienced by rebar workers. Design/methodology/approach: In all, 20 healthy male participants performed simulated repetitive rebar lifting tasks with three different lifting weights, using either a stoop (n = 10) or a squat (n = 10) lifting posture, until subjective fatigue was reached. During these tasks, trunk muscle activity and spinal kinematics were recorded using surface electromyography and motion sensors, respectively. Findings: A mixed-model, repeated measures analysis of variance revealed that an increase in lifting weight significantly increased lower back muscle activity at L3 level but decreased fatigue and time to fatigue (endurance time) (p < 0.05). Lifting postures had no significant effect on spinal biomechanics (p < 0.05). Test results revealed that lifting different weights causes disproportional loading upon muscles, which shortens the time to reach working endurance and increases the risk of developing LBDs among rebar workers. Research limitations/implications: Future research is required to: broaden the research scope to include other trades; investigate the effects of using assistive lifting devices to reduce manual handling risks posed; and develop automated human condition-based solutions to monitor trunk muscle activity and spinal kinematics. Originality/value: This study fulfils an identified need to study laboratory-based simulated task conducted to investigate the risk of developing LBDs among rebar workers primarily caused by repetitive rebar lifting.