A night vision device (NVD) equipped on a ballistic helmet violates the locational stability of a helmet, and sweating remaining inside a helmet can also reduce helmet stability. This study aimed to investigate the combined effect of sweating and mounting a NVD on helmet stability. Nine healthy males participated in the experiments which consisted of military simulated tasks and 20 min walking. Subjective evaluations containing helmet stability and comfort along with physiological measurements such as microclimate inside a helmet and sweating rate were obtained. Local sweat rate on the forehead was predicted by sweat rate on the upper back and forearm. The results showed that (1) mounting a NVD did not significantly influence on helmet stability per se before onset of sweating, however, (2) when it is combined with sweating, helmet stability reduced 50% during shooting in a prone position (P < 0.05). (3) There was a significant correlation with helmet overall comfort and helmet stability (r = 0.762, P < 0.05), and between helmet stability and helmet pressure (ρ = 0.701, P < 0.05). The present study demonstrated that mounting additional devices on the helmet violates helmet stability when accompanied by sweating, even when optimized fit provided and that just tightening bands cannot be an absolute solution. This study emphasized the importance of helmet stability as a variable for evaluating helmet comfort.

中文翻译：

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面部出汗和安装夜视仪对头盔稳定性的综合影响

配备在防弹头盔上的夜视仪（NVD）破坏了头盔的位置稳定性，并且头盔内残留的汗水也会降低头盔的稳定性。这项研究旨在调查出汗和安装NVD对头盔稳定性的综合影响。9名健康男性参加了由军事模拟任务和20分钟步行组成的实验。获得了包含头盔稳定性和舒适性以及生理指标（例如头盔内的微气候和出汗率）的主观评估。通过上背部和前臂的出汗率来预测前额的局部出汗率。结果表明：（1）在开始出汗之前，安装NVD本身对头盔稳定性没有明显影响，但是，（2）与出汗一起使用时，俯卧位射击时头盔稳定性降低50％（P <0.05）。（3）与头盔的总体舒适度和头盔稳定性之间存在显着相关性（r = 0.762，P <0.05），并且与头盔稳定性和头盔压力之间存在显着相关性（ρ= 0.701，P <0.05）。本研究表明，在头盔上安装附加设备会在出汗时破坏头盔的稳定性，即使提供了最佳的贴合度，仅系紧绑带也不是绝对的解决方案。这项研究强调了头盔稳定性作为评估头盔舒适度的变量的重要性。本研究表明，在头盔上安装附加设备会在出汗时破坏头盔的稳定性，即使提供了最佳的贴合度，仅系紧绑带也不是绝对的解决方案。这项研究强调了头盔稳定性作为评估头盔舒适度的变量的重要性。本研究表明，在头盔上安装附加设备会在出汗时破坏头盔的稳定性，即使提供了最佳的贴合度，仅系紧绑带也不是绝对的解决方案。这项研究强调了头盔稳定性作为评估头盔舒适度的变量的重要性。