Firefighter Helmets and Neck Muscle Fatigue

This study investigates how helmet properties—mass and center of mass (COM)—influence neck muscle fatigue to support the biomechanical design of firefighter helmets. Thirty-six firefighters (18 males, 18 females) performed sustained neck flexion and extension tasks under three conditions: no-helmet, US, and European-style (EU) helmets. Electromyography (EMG) data from eight neck muscles were collected. Fatigue was assessed using increases in normalized mean absolute value (NMAV) and decreases in median frequency (MF) of EMG signals. Signals were segmented into four intervals (0%–25%, 26%–50%, 51%–75%, 76%–100%), and regression analyses and ANOVA were applied to evaluate NMAV and MF values. Results showed that the US helmet led to greater muscle activation and fatigue. These findings highlight the importance of optimizing COM location—not just weight—when designing helmets to reduce neck injury risks.