Introduction: Musculoskeletal disorders are a major part of occupational diseases in working environments. The aim of this study was evaluates the risk factors of musculoskeletal disorders by the assessment of Muscle Fatigue Assessment method (MFA). It also sought to determine the effects of an ergonomic intervention on the mentioned risk in an Assembly industry.

Methods: This study conducted on 15 people working in the Assembly line. Medical records of Assembly line workers were reviewed and Nordic Musculoskeletal Questionnaires (NMQ) after one year of intervention was completed. Activities of these workers in Assembly line were evaluated by Muscle Fatigue Assessment method (MFA) and workers were given the necessary training. Data were analyzed in SPSS-16.

Results: The initial evaluations showed that neck, back, leg and knee, respectively in 6.67, 20 and 13.33 percent were in the "very high" priority corrective measures. Re-assessments after the intervention showed that Percent of people with musculoskeletal disorders in the neck in the "very high" corrective actions changed to zero. The percent of organs at the level of "high" corrective actions before the intervention was greatly reduced. For example, around the waist from 60% to 33.33% and neck from 53% to 26.27% after intervention were reduced. A total of 30 cases of abnormalities detected before the intervention, after intervention, this number reduced to 11.

Conclusion: According to MFA Score, risk of musculoskeletal disorders was reduced by intervention in this industry and According to Questionnaire, prevalence of musculoskeletal disorders also significantly reduced.