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Introduction: The firefighting helmet, as one of the key pieces of personal protective equipment, exacerbates firefighters’ fatigue when worn for long periods, in addition to the stress and physical exhaustion experienced in the field. To address this issue, there is a growing demand for a standardized testing protocol to objectively evaluate various helmet designs and to guide improvements that enhance comfort and reduce physical strain. The objective of this study was to quantitatively assess cervical muscle activity during the acceleration and deceleration phases of head extension, rotation, and lateral flexion at two different movement speeds, both with and without the standard firefighter helmet used in South Korea.

Methods: Twenty healthy young adults (10 females and 10 males) voluntarily participated in the study. Participants were instructed to perform controlled head movements – extension, rotation, and lateral flexion – within a fixed range, both with and without wearing the standard firefighter helmet used in South Korea. Each movement was executed at two predetermined angular velocities: 45 and 75 revolutions per minute (rpm). Electromyographic (EMG) data were collected from the sternocleidomastoid (SCM), cervical erector spinae (CES), upper trapezius (TRA), and splenius capitis (SPC) muscles during the acceleration and deceleration phases of each motion, using the Polhemus Liberty™ motion tracking system and Delsys Trigno™ wireless EMG sensors.

Results: The SCM during extension, the SPC and SCM during rotation, and the CES and TRA during lateral flexion demonstrated the greatest changes in muscle activity due to helmet use. The biomechanical impact of the helmet varied across acceleration and deceleration phases, depending on the direction of head movement. Notably, increased head motion speed was associated with elevated muscle activation particularly during deceleration with helmet in the aforementioned muscle groups.

Discussion: Based on the results of this study, we aim to provide ergonomic experimental data necessary for the development of firefighter helmets and offer objective evidence for improved helmet design. In the future, when a new helmet is developed, its usefulness will be evaluated by testing how much less it burdens the neck muscles compared to existing helmets.

Conclusion: This study found that wearing a standard firefighter helmet increases cervical muscle activity, especially during faster head movements and deceleration phases. The results highlight the need for improved helmet designs that reduce neck strain and support the development of standardized testing protocols to enhance firefighter comfort and safety.