Iran Occupational Health

  Background and aims : Long term working in a static and awkward posture is known as an important risk factorof work related musculoskeletal disorders in hand carpet weavers. Inappropriate workstation and awkward posture can increase the electrical activity and fatigue in muscles. The aim of this study was the measurement of muscle load and fatigue by surface electromyography and Borg CR-10 scale methods.

  Methods: Two typical carpet weaving workstations (A: seated with cross legged posture and B: seated on chair) were simulated in the laboratory and 12 women carpet weavers with mean age of 32.5 years, without any musculoskeletal problems in upper limb were invited to this study and they were asked to work in each workstation in separate days for 3 hours. Surface EMG signal recordings were done during these 3 hours for four muscles (bilateral trapezius and bilateral deltoid) andall subjects were asked to report shoulder region fatigue in Borg CR-10 rating scale. The RMS and MF values were extracted form row EMG signal to estimate the muscle activity and fatigue.

  Results: The result of this study shown that muscle activity in all muscles under the test in workstation A is higher than workstation B (P <0.05). In comparison between the muscles, the mean RMS of the trapezius is higher than bilateral deltoid (P<0.01). Joint analysis of spectral and amplitude for estimating the muscle fatigue shown that muscle fatigue incidence in workstation B is more than workstation A. In comparison between Borg CR-10 rating scale, there is no significant difference in two workstations.

  Conclusion: According to these results, it can be concluded that working in two workstations can increase the risk of work related musculoskeletal disorders in shoulder region and further studies and hence, designing the ergonomic workstation for carpet weavings is necessary