Static Optimization-Based Cervical Spine Load Estimation to Evaluate Firefighter Helmet Effects

Abstract

Firefighters’ helmets were linked to increased neck muscle strain and potential cervical spine degeneration due primarily to their weight and inertial properties. This study investigated how helmet mass, center of mass (COM), and moment of inertia (MOI) affect cervical joint reaction forces (JRFs) during head-neck flexion-extension (FE) movements. Five male and five female firefighters performed dynamic flexion-extension and static flexion and extension tasks under three conditions: no-helmet, a US-style helmet, and a European (EU) helmet. Subject-specific OpenSim models were developed to estimate three-dimensional cervical JRFs from C0–C1 to C7–T1. Results showed that the US helmet, despite being lighter, induced higher compressive and shear forces than the EU helmet due to its superiorly shifted COM and higher MOI. These findings highlight the role of lowering the COM on the helmet design to reduce spinal loading and the injury risk. Future studies should incorporate lateral and rotational movements and sex-specific modeling.