Davood Afshari

The impact of ergonomics intervention on trunk posture and cumulative compression load among carpet weavers.

BACKGROUND Work-related musculoskeletal disorders of back among weavers are prevalent. Epidemiological studies have shown an association between poor working postures and back disorders among carpet weavers. Therefore, the present study aimed to evaluate the impact of the traditional (A) and ergonomically designed (B) workstations on trunk posture and cumulative compression load in carpet weavers. METHODS In this study, subtasks were identified in terms of stressful postures and carpet weaving process. Postural data were collected during knotting and compacting subtasks using inclinometer during four hours for each workstation. Postural data, weight and height of the weavers were entered into the University of Michigan three-dimensional static biomechanical model for estimation of the compression load and cumulative load were estimated from the resultant load and exposure time. PARTICIPANTS Thirteen healthy carpet weavers (four males and nine females) participated in the study. RESULTS Median trunk flexion angle was reduced with workstation B during knotting subtask (18° versus 8.5°, p< 0.01 in males; 18.5° versus 7°, p< 0.001 in females). Average cumulative compression load was reduced with workstation B (22.17MN-s versus 16.68MN-s, p < 0.01 in males; 13.05 MN-s versus 10.14, p < 0.001 in females). CONCLUSIONS Using workstation B led to significant decrease in cumulative compressive loading during an entire shift (8 hours), which indicates reduced level of stress on the back. It is suggested to conduct biomechanical studies on the shoulder and wrist regions in carpet weavers in order to achieve further development and improvement in the ergonomically designed workstation.

Full shift assessment of back and head postures in overhead crane operators with and without symptoms

Prolonged sitting with a flexed back and neck is recognized as being associated with an increased risk of neck and back pain disorders among overhead crane operators. The aim of this study was to compare back and head postures over a full shift of work between operators who experience back and neck pain, and healthy operators.

Physical workload and musculoskeletal disorders in back, shoulders and neck among welders

This study aimed to determine the effect of the physical workload on the back, neck and shoulders of welders. The prevalence of musculoskeletal symptoms was assessed using the Nordic questionnaire among 15 welders. The physical workload of the neck, back and upper arms was then measured by means of inclinometry as the welders were working. The results revealed that the highest prevalence of musculoskeletal disorders during the previous 12 months was in the lower back and shoulders. The median trunk and neck flexion were significantly associated with back and neck pain in welders with symptoms during the past year (p < 0.05). Physical exposure in welders with pain was characterized by significantly more awkward postures and percentage of time spent with the trunk and neck flexed more than 20°. The nature of their work and the design of their workstations may be causes of the symptoms they experienced during work.

Effect of neck posture on cervicothoracic loads in overhead crane operators

Awkward neck postures are commonly documented to be associated with an increased risk of neck disorders. This study intended to continuously monitor and evaluate neck postures and to estimate the cervicothoracic loads among overhead crane operators during work time. Neck postures were measured among 40 randomly selected operators by an inclinometer during 2 h of work time. To determine the tasks and adapt the posture recordings to each of their corresponding tasks, direct observation was conducted concurrently. The median neck flexion and lateral bend angles were 28.23° and 11.30°, respectively. The mean compression and shear loads on the neck ranged from 75.22 to 113.14 N and from 9.50 to 41.11 N, respectively. The results indicated substantial levels of exposure to awkward and extreme neck postures among the operators. The nature of the operators’ work and the visual requirements of some tasks will increase the mechanical loads on the neck.

Assessment of low back disorders risk based on allowable weight limits for manual lifting in Iran

In 2011, load limits for manual lifting were adopted in Iran to protect workers from low back injury without prior testing of accuracy with Iranian workers. This investigation examined how accurate the adopted ACGIH TLVs at the allowable limits predict risk for LBP disorders for a group of Iranian workers using biomechanical criteria. Testing took place in the laboratory with participants completing a series of 2-handed lifting tasks as defined in the Iranian Guideline for Manual Lifting. To test accuracy, both compression and shear forces were estimated for fifteen male Iranian workers who completed 25 lift combinations that varied in height and reach with the maximal allowable load. The findings, when compared to a risk threshold of 3400 N compression and 700 N shear, showed above-threshold forces for compression and little-to-no safety margins with repetitive lifting for most lifts at torso height and below. Since Government, employers and workers use these guidelines to decide on work/workplace design; these guidelines require further review and revision based on the anthropometrics of Iranian people.