Firefighter Helmets and Cervical Intervertebral Kinematics: An OpenSim-Based Biomechanical Study

The assessment of cervical intervertebral kinematics can serve as the basis for understanding any degenerative changes in the cervical spine due to the prolonged wear of a heavyweight, imbalanced firefighting helmet. Therefore, this study aimed to analyze cervical intervertebral kinematics using OpenSim musculoskeletal modeling platform in order to provide much-needed insights of how the inertial properties of firefighter helmet affect cervical spinal mobility. A total of 36 firefighters (18 males and 18 females) were recruited to perform static and dynamic neck flexion, extension, and left and right lateral bending tasks for three conditions: 1) no-helmet, 2) US-style helmet with a comparatively superior center of mass (COM), and 3) European-style helmet with relatively higher mass but an inferior COM. Three custom-made OpenSim head-neck models were created to calculate cervical intervertebral kinematics for each helmet condition. Results showed that the helmet use significantly (p<0.001) affects neck and cervical spinal kinematics. Especially, the superior COM placement in the US-style helmet, despite its lighter weight, caused more pronounced kinematic changes and quicker attainment of peak flexion and extension angles compared to the European-style helmet across all cervical joints. Moreover, results also revealed discrepancies between OpenSim-derived neck and cervical range-of-motion and those reported in previous in-vivo studies. In conclusion, the present study underscores the importance of designing firefighter helmets with a lower profile (less superior COM) to enhance neck range of motion and minimize potential neck injuries.