Are hard hats a risk factor for WRMSD in the cervical-thoracic region?

OBJECTIVES: To investigate the effect of wearing hard hats on the lower cervical and upper thoracic region using surface electromyography (sEMG) and possible link to work-related musculoskeletal disorder (WRMSD). METHODS: Twenty study subjects wore sEMG sensors placed on the upper trapezius muscle on their dominant side to assess muscle activity while wearing different hard hats. Study subjects were asked to don six different hard hats and assume varied neck postures. A repeated-measures design was used to analyze the results for difference and similarities in muscle activity. RESULTS: There was a small, significant effect of wearing a hard hat on muscle loading in the upper trapezius (p = 0.038). Post-hoc analyses revealed the only statistically significant difference was between wearing no hard hat at all and wearing head protection (without accessories) in the flexed posture (p = 0.006). CONCLUSION: The results demonstrated that there was little difference in lower cervical and upper thoracic muscle activity while donning a hard hat and assuming various neck postures. Wearing a sample of commonly used hard hats in this study does not appear to substantially increase muscle activity that would cause fatigue in the lower cervical and upper thoracic region among young, healthy volunteer subjects.