Foot Biomechanics, Body Composition, and Sex‐Related Factors Associated With Work‐Related Musculoskeletal Discomfort in Standing Assembly‐Line Workers: A Cross‐Sectional Study

BACKGROUND: Prolonged standing is common in manufacturing and assembly-line work and is associated with musculoskeletal discomfort, especially in the lower limbs and spine. The influence of foot posture, morphology, and plantar loading patterns on this discomfort remains unclear. OBJECTIVE: To analyze the associations between foot posture, plantar pressure, and 3D foot morphology with work-related musculoskeletal discomfort in standing workers and to examine the role of BMI and the potential modifying role of sex. METHODS: A cross-sectional study was conducted among 240 assembly-line workers (129 women, 53.8%). Musculoskeletal discomfort was assessed using the Cornell Musculoskeletal Discomfort Questionnaire (CMDQ). Foot posture (FPI-6), baropodometry (FreeMed), and 3D foot morphology (DOMESCAN) were evaluated under standardized conditions. Participants were classified as having low (CMDQ ≤ 10) or moderate-high (≥ 11) discomfort. Firth-penalized logistic regression analyzed associations between overall CMDQ discomfort, foot posture, sex, and BMI, including an FPI × sex interaction term. RESULTS: All workers reported at least one musculoskeletal discomfort response, with the feet, neck, and lumbar region accounting for the largest proportions of reported discomfort. Among women, pronated foot posture was associated with higher odds of moderate-high overall CMDQ discomfort (OR = 2.91, 95% CI 1.10-7.28). Overweight/obesity status was associated with higher odds of foot and hip/gluteal discomfort, whereas, among women, pronated foot posture was associated with greater odds of lumbar discomfort. The pronation-discomfort association was stronger in women and attenuated in men. CONCLUSIONS: Among women, pronated foot posture was associated with greater overall work-related musculoskeletal discomfort during prolonged standing and with greater odds of lumbar discomfort, whereas overweight/obesity status was associated with greater odds of foot and hip/gluteal discomfort. The pronation-discomfort association was attenuated in men. From an occupational-health perspective, incorporating foot-posture and BMI assessment into ergonomic evaluations may help identify workers who could benefit from more individualized preventive strategies, particularly women with pronated feet.