Presentation
Impacts of Helmet Inertial Properties on Neck Muscle Fatigue
DescriptionThis study investigates how helmet inertial properties—mass, center of mass (COM), and moment of inertia (MOI)—influence neck muscle fatigue to support the biomechanical design of firefighter helmets. A total of 36 firefighters (18 males, 18 females) performed sustained neck flexion and extension tasks under three conditions: no-helmet, US, and European-style (EU) helmets. Neck angles, endurance time, Borg’s discomfort ratings, and electromyography (EMG) data from left and right infrahyoid, sternocleidomastoid, cervical trapezius, and upper trapezius muscles were recorded. 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 slopes. Results showed that the US helmet (with a 5.8 cm superior COM from the atlantooccipital joint than the EU helmet) caused higher muscle activation, accelerated muscle fatigue, increased discomfort, and reduced neck endurance than the EU helmet despite being 250g heavier than the US helmet. The findings indicated that when designing helmets for safety-critical occupations like firefighting, the COM properties should be prioritized alongside its weight considerations in order to reduce the risk of fatigue-induced neck musculoskeletal injuries.
Event Type
Lecture
TimeWednesday, October 15th11:50am - 12:10pm CDT
LocationGrand C/D South
Occupational Ergonomics
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