Musculoskeletal ailments in Indian injection-molded plastic furniture manufacturing shop-floor: Mediating role of work shift duration

• SMA is prevalent in plastic furniture manufacturing industries in India.
• WSD, WP, WD and SMA are significantly correlated.
• WSD has mediation effect upon WD and WP for predicting occurrence of SMA.
• Proposed ‘mediation model’ is first of its kind in occupational health research.
• Findings would help in formulation of ergonomics intervention strategies.

The present manuscript aims to investigate the occurrence of awkward working postures and the consequent prevalence of the Symptoms of Musculoskeletal Ailments (SMA) among the shop floor workers of Indian small and medium scale injection molded plastic furniture manufacturing factories. An attempt has also been made to assess the contributing role of Workstation Design (WD), Working Postures (WP) and Work Shift Duration (WSD) concerning symptoms of musculoskeletal ailments and to find out the inter-relationships among all these factors. Direct observation aided by photography helped to observe working methods, postures and the design of workstations. The prevalence of SMA was evaluated using Standardized Nordic Questionnaire and awkward WP by postural assessment tools like Ovako Working posture Analysis System (OWAS) and Rapid Entire Body Assessment (REBA). SMA was significantly (p < 0.001) higher for shop-floor workers compared to administrative and supervisory employees. Mediation statistics (using correlation and regression) was employed to analyze the stand-alone/cumulative impact(s) of WP, WD and WSD in determining SMA. Awkward WP, prolonged WSD and bad WD were established as the significant risk factors for higher prevalence of SMA for shop-floor workers. Influence of WP and WD on SMA was found to be significantly (p < 0.05) mediated through WSD. It was established through statistical modeling that occurrence of SMA due to awkward WP and bad WD is further exacerbated if WSD is prolonged. These findings would have constructive contributions in framing ergonomic intervention strategies and articulating methodological stipulations for work design to dwindle the SMA in shop-floor workers of the Indian small and medium scale injection-molded plastic furniture manufacturing factories.Relevance to industrySymptoms of Musculoskeletal Ailments (SMA) due to awkward working posture and bad workstation design are exacerbated in prolonged work shift duration. Regulating work shift duration could be a possible ergonomic intervention strategy to curb SMA, if the scope for workstation and work method redesign towards avoiding awkward posture is limited.