Abstract

Firefighters’ protective clothing (FPC) can limit human thermoregulation due to limited water vapor permeability and insulation. This study investigated the effect of cooling on the physiological responses and probability of hyperthermia in subjects wearing FPC during exercise in a hot environment. Twelve males participated in this study. A maximal graded treadmill exercise test was performed to measure maximal oxygen uptake ($\dot{V}$O_2max) and to assess subjects’ capacity to perform the assigned exercise. Exercise included treadmill walking at 40% $\dot{V}$O_2max in warm (30 °C) and humid (70% RH) conditions for 40 min while wearing FPC. Subjects participated in two randomly counterbalanced assigned experimental protocols: control (no cooling) and intervention (cooling). The experimental intervention consisted of a cooling garment infused with cooled water (18 °C) through silastic tubing sewn into the fabric and worn underneath FPC. Each subject served as their own control and, therefore, completed both the control and intervention of the protocol. A logistic regression model was used to analyze the interaction effect of cooling on the probability of progression to hyperthermia (T_c ≥ 38 °C). Subjects’ physiological responses increased during exercise in a warm and humid environment. Active cooling decreased (p < 0.05) the thermal stress thereby reducing the probability of hyperthermia while exercising in hot and humid conditions. The results indicate that when cooling was used each subject, on average, was 91% less likely to reach the lower threshold limit of hyperthermia. Exercise in hot environments while wearing FPC results in significant physiological strain, which may lead to hyperthermia. Utilization of a cooling garment reduced physiological strain and the probability of hyperthermia.

摘要

由于水蒸气渗透性和绝缘性有限，消防队员的防护服 (FPC) 会限制人体的体温调节。本研究调查了佩戴 FPC 的受试者在炎热环境下运动时冷却对生理反应和体温过高概率的影响。十二名男性参与了这项研究。进行最大分级跑步机运动测试以测量最大摄氧量（$\dot{V}$O _2max）并评估受试者执行指定练习的能力。运动包括跑步机步行 40%$\dot{V}$佩戴 FPC 时，在温暖 (30 °C) 和潮湿 (70% RH) 条件下，O _{2max 40 分钟。}受试者参加两个随机平衡分配的实验方案：控制（不冷却）和干预（冷却）。实验干预措施包括通过缝在织物中的硅橡胶管注入冷却水（18°C）的冷却服，并穿在 FPC 下方。每个受试者都充当自己的对照，因此完成了协议的控制和干预。_{使用逻辑回归模型分析降温对进展为高热（T c} ≥ 38 °C）概率的交互作用。在温暖潮湿的环境中锻炼时，受试者的生理反应会增强。主动冷却可降低 (p < 0.05) 热应力，从而降低在炎热和潮湿的条件下运动时出现体温过高的可能性。结果表明，当使用降温措施时，每个受试者达到高热阈值下限的可能性平均降低 91%。佩戴 FPC 在炎热环境中运动会导致明显的生理压力，从而可能导致体温过高。使用冷却服可以减少生理压力和体温过高的可能性。