Work-related musculoskeletal disorders among informal metal fabrication workers in small urban centres of Zimbabwe

Abstract

The use of awkward working postures and repetitive movements in metal fabrication may elevate the risk of developing work-related musculoskeletal disorders (WRMDs). The objectives of the study were to (i) assess the potential ergonomic risk factors for WRMDs among metal fabrication workers, (ii) assess the prevalence, severity and risk factors for WRMDs, and (iii) determine the effects of ergonomic training on postural risk and the effects of combined ergonomic training and stretch exercises on pain severity reported by metal fabrication workers in the informal sector of Zimbabwe. The Preferred Reporting Item for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used to identify and screen the articles. A pre-designed criterion was used for evidence synthesis. The Modified Cornell Musculoskeletal Questionnaire (MCMQ) was used to assess prevalence, severity and risk factors for WRMDs, and the Quick Exposure Check (QEC) and the Rapid Entire Body Assessment (REBA) were used to conduct postural risk assessment. Two hundred sixty metal fabrication workers were purposively selected and randomly assigned to four groups. Supervised training and exercise sessions were conducted for a period of 11 weeks. A total of 189 metal fabrication workers finished the intervention programme. Potential ergonomic risk factors for WRMDs among metal fabrication workers data were analysed a pre-designed criterion. Prevalence, severity and risk factors were analysed using binary logistics regression, multinomial logistics regression and the paired t-test was used to assess the effects of ergonomic training and stretch exercise. All analyses were conducted in the Statistical Package for Social Science (SPSS) version 25.0. Prolonged working hours using awkward postures were consistently reported to contribute to the development of WRMDs. A high prevalence of pain in the lower back (78%), right shoulder (66%), left hand wrist (62%) and right-hand wrist (61%) was reported. With regards to the severity of lower back pain, 4% reported low pain, 24% mild pain and 48% severe pain. Elevated grand REBA scores were significantly associated with self-reported pain at the lower back (OR = 1.48, 95% CI 1.13 - 1.94), right shoulder (OR = 1.48, 95 CI 1.14 - 1.92) and left shoulder (OR = 1.28, 95 CI 1.04 - 1.57). The multinomial regression analyses showed that smoking, prolonged working hours and not engaging in physical activities were significant predictors for pain. High job satisfaction and taking adequate work-rest breaks were key protective factors for WRMDs (p < 0.05). The risk for developing WRMDs on several body regions (shoulder/arm, hand/wrist and neck) significantly reduced after the administration of an ergonomic training program (p = 0.001). In the combined ergonomic training and stretch exercise group, there was a significant reduction of reported pain in most body regions (p = 0.001). In conclusion the study showed that (i) there is a high prevalence of WRMDs among metal fabrication workers due to individual and work-related risk factors, (ii) interventions such as ergonomics education are required to address the risk factors for and progression of WRMDs among metal fabrication workers, (iii) that there is need for improved study designs that implement and evaluate interventions to reduce the risk, prevalence and severity of WRMDs among metal fabrication workers, and (iv) there is need for ergonomics education, ergonomically designed workstations, and stretch exercises, to reduce the severity of pain among metal fabrication workers.

Keywords: Awkward Working Posture; Ergonomic Risks; Metal Fabrication; Work-Related Musculoskeletal Symptoms; WRMDs.