EVALUATION OF DISTAL UPPER EXTREMITY (DUE) MUSCULOSKELETAL DISORDERS BY STRAIN INDEX (SI) IN AN IRONWORK INDUSTRY

Work-related musculoskeletal disorders (WMSDS) is one of the most important problems in working populations of Iranian industries; so, in order to evaluate the integrated roles and effects of various ergonomic risk factors inducing such disorders, the Strain Index (SI) methods was used. This was a cross-sectional study conducted on 448 male subjects including 63 controls working in administrative jobs and 385 cases working in lathing, welding, melting and foundry jobs using integrated procedure which includes observations, interview, Nordic Musculoskeletal Questionnaire (NMQ) methods and SI model. All workers were questioned. Data were analyzed using SPSS software v. 11 and Excel package. The most prevalent MSDs in upper limbs were found in melting lathing, foundry and welding respectively. There was a significant relationship between age and job groups (c =7.33; df=16; p<0.001). One-way analysis of variance showed a significant differences among means of calculated Strain Indices of administrative (1.06), lathing (6.52), welding (3.68), melting 7.79) and foundry (6.33) jobs (F=5.92; df=16; p=0.005). Also it was revealed that melting job was attributed as "hazardous job" (4 risk level), lathing and foundry jobs were referred to "moderate risk level" (3 risk level), welding job was allocated as "uncertain risk level" (2 risk level), and administrative job was attributed as "safe risk level" (1 risk level). Moreover, there was a significant relationship between DUE and job groups (c2=11.92; df=12; p=0.004).The paired ttest showed significant difference with direct and relatively complete correlation between means of Strain Indices in right (6.53) and left (4.29) hands (r=0.69; t=3.15; p<0.001). The Strain Index (SI) model can be referred as an efficient and applicable method for the assessment of ergonomics risk factors inducing upper extremity musculoskeletal disorders (UEMSDs), classifying jobs, correcting and modifying work situations and preventing DUE musculoskeletal disorders.