Individual variability in lumbar muscle activation with passive back-support exoskeletons: an EMG study of experienced construction workers

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Purpose While back-support exoskeletons (BSE) have shown promise in laboratory studies during repetitive tasks, their effectiveness during realistic construction tasks with experienced workers remains poorly understood. This study evaluates the effectiveness of two commercially available BSE designs in reducing lumbar muscle activation during actual simulated masonry work and examines individual response variability among construction workers. Design/methodology/approach Twenty-three experienced masons performed standardized masonry activities involving concrete masonry units under three conditions simulated in a laboratory environment: no exoskeleton (baseline), HAPO exoskeleton and BISKO exoskeleton. Surface electromyography (sEMG) measured bilateral lumbar erector spinae (LES) muscle activation. Statistical analysis compared muscle activation changes between conditions and characterized individual worker responses using within-subject comparisons and group-level testing. Findings HAPO demonstrated superior effectiveness, achieving mean reductions of 10.0% (right LES) and 11.5% (left LES) in muscle activation, compared to BISKO's 3.4% and 7.0% reductions, respectively. However, individual responses varied substantially, ranging from 50% reductions to increased activation in some workers. Both exoskeletons showed consistently better performance for left LES compared to right LES, indicating significant bilateral asymmetry. Statistical analysis revealed that individual worker characteristics and established movement patterns from years of experience significantly influenced exoskeleton effectiveness. Originality/value This study addresses critical gaps by evaluating exoskeletons with real construction workers performing realistic masonry tasks, rather than laboratory volunteers with simplified activities. The comprehensive analysis of individual response variability challenges universal effectiveness assumptions and demonstrates that experienced workers' established movement patterns critically influence intervention outcomes. Results provide evidence for individualized implementation strategies rather than universal deployment approaches in occupational settings.

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