Ergonomic evaluation of passive lower-limb exoskeletons in simulated industrial tasks at non-optimal workstations

Background Industrial tasks often require workers to maintain awkward static postures at non-optimal workstations, leading to physical strain and musculoskeletal issues. Exoskeletons offer potential ergonomic benefits by reducing physical workload. However, the efficacy of passive lower-limb exoskeletons in non-optimal workstation conditions remains unclear. Objectives This study examines the ergonomic efficacy of a passive lower-limb exoskeleton during simulated industrial tasks performed at workstations with varying heights and tilt angles. Methods Sixteen participants performed bolting tasks at workstations configured at two heights (60 cm and 90 cm) and three tilt angles (0°, 45°, and 90°), under exoskeleton and non-exoskeleton conditions. Assessments included muscle activity (erector spinae and rectus femoris), joint angles (lumbar, hips, and knees), segmental REBA scores, perceived exertion, and perceived discomfort. Mixed-effects and generalized linear mixed models evaluated the impact of workstation conditions and exoskeleton use. Results The exoskeleton reduced erector spinae muscle activity by an average of 39% and supported more neutral hip and knee postures ( p < 0.001), though it increased rectus femoris activity at the higher workstation ( p < 0.001) and segmental REBA scores for the trunk and leg under specific conditions ( p < 0.001). Furthermore, although exoskeleton use did not have a significant effect on perceived exertion or discomfort, workstation height significantly influenced both variables ( p < 0.001 and p < 0.05, respectively). Conclusions The passive lower-limb exoskeleton may reduce specific muscle loads and improve posture in non-ideal settings, though its efficacy varies by workstation configuration.