External cervical spine joint moments in pilots during high +Gz real–flight: a biomechanical analysis using individual opensim models

The cervical spine of fast jet pilots is exposed to high +Gz accelerations during large range of head movements which may lead to biomechanical impairments. The objective of this study therefore was to quantify and analyze the resulting external cervical spine joint moments experienced by fast jet pilots during standardized head movements in real–flight during +5Gz, +7Gz and +9Gz maneuvers. The in– flight helmet orientation recordings and additional ground based motion capture recordings of isolated head movements of seven Eurofighter pilots were processed using a custom made pipeline. Subsequent inverse kinematics and inverse dynamics simulations of the in–flight head movements using individual OpenSim pilot models showed a significant reduction in the head extension angle with increasing +Gz acceleration. Cervical spine joint moments did not change significantly with increasing +Gz acceleration. However, theory–based model analysis indicated that constant head positions under higher +Gz acceleration would lead to an increase in joint moments. The pilots seemed to exhibit reduced head extension at higher +Gz levels, while external joint moments remained relatively constant. Furthermore, the designed pipeline may support individual cervical spine health assessment and monitoring, as well as to inform strength training or rehabilitation programming.