Digital human modeling for occupational health of rice mill workers in manual materials handling

BackgroundHeavy loads are carried out manually by rice mill workers, which causes a considerably high compressive force on the spine, particularly in the L4-L5 region.ObjectiveTo assess the posture and discomfort experienced by the rice mill workers in manual materials handling (MMH) tasks. To estimate the moment and back compressive force (BCF) at L4-L5 using digital human modeling (DHM).MethodsThe posture of 12 males was measured for three MMH tasks and three modes of load carrying. The measured posture was analyzed using the Kinovea software. A manikin was developed using CATIA software to estimate the moment and BCF. The Rapid Upper Limb Assessment (RULA) discomfort score was estimated on the developed manikin. A survey was carried out using a modified Nordic questionnaire to assess the discomfort among the workers.ResultsThe torso flexion varied from 39.6° to 52° and 3.4° to 7.7° for load carrying on back and on head, respectively. The moment and BCF at L4-L5 were significantly (p < 0.05) higher for load carrying on back as compared to load carrying on head. The BCF at L4-L5 during load carrying on back was higher than the threshold limit of 3400 N. The RULA score during load carrying on back was 5 on 7-point scale. The mean discomfort score was relatively higher on the lower back and upper back.ConclusionsRULA score and BCF suggest the need for intervention to reduce discomfort and compressive force at L4-L5 among rice mill workers.