Laboratory and field evaluation of user-perceived effort, comfort, and acceptance of passive back-support exoskeletons for masons

Work-related musculoskeletal disorders affect over 30 % of construction workers globally, with back injuries particularly prevalent among masons who handle approximately 10,000 kg of masonry units daily. These injuries represent a critical occupational safety challenge, with masonry workers experiencing overexertion rates 33.4 per 10,000 FTEs compared to 21.5 across all industries. While back-support exoskeletons (BSEs) show promise as injury prevention interventions, most safety evaluations occur in laboratories, raising questions about real-world protective effectiveness. This study compared BSE performance between laboratory and field settings to assess ecological validity for occupational safety applications. A multiple case study examined two passive BSEs: HAPO (rigid, spring-based) and BISKO (soft, elastic-based), testing 23 laboratory and 15 field masons performing masonry tasks using psychophysical assessments. HAPO demonstrated superior laboratory performance (median overall score: 1.5) but significant field deterioration (median: 3.0, p < 0.001), with physical effort ratings increasing 200 % (median: 1.0 to 3.0) and movement restriction ratings doubling (median: 1.0 to 3.0). BISKO maintained stable performance across settings (median overall scores: laboratory 2.25, field 1.875, p = 0.217). Worker willingness to continue using HAPO declined sharply from laboratory (median: 1.0) to field (median: 4.0), suggesting potential non-adoption and continued injury risk. Laboratory testing inadequately predicts field safety performance. These findings necessitate field-validated protocols for exoskeleton safety assessment and highlight design importance for sustained injury prevention. Successful implementation requires prioritizing extended-wear comfort and movement flexibility over maximum support to ensure worker acceptance and sustained protective benefit.