Montana Center for Work Physiology and Exercise Metabolism, The University of Montana, 32 Campus Drive, Missoula, MT 59812-1825, United States.
J Therm Biol. 2014 Oct;45:134-40. doi: 10.1016/j.jtherbio.2014.08.009. Epub 2014 Sep 1.
The purpose of this study was to determine changes in physiological markers of heat acclimatization across a 4-month wildland fire season. Wildland firefighters (WLFF) (n=12) and non-WLFF (n=14) were assessed pre- and post-season for body mass, percent body fat, and peak VO₂. Both groups completed a 60-min heat stress trial (walking at 50% of peak VO₂) in a climate controlled chamber (43.3 °C, 33% RH) pre and post-fire season (May through September). During the trials, core (Tc) and skin (Tsk) temperatures, heart rate (HR), physiological strain index (PSI), and rating of perceived exertion (RPE) were measured. There were no differences pre or post-season between the WLFF and non-WLFF groups in body mass, percent body fat, or peak V.O2. During the 73 days where the WLFF were involved in direct wildland fire suppression, daily high temperature for the WLFF was higher compared to the non-WLFF, 30.6 ± 5.4 °C and 26.9 ± 6.1 °C, respectively, p<0.05. Tc was lower at post-season compared to pre-season (p<0.05) for the WLFF at 30, 45, and 60 min (pre 30, 45, and 60: 37.9 ± 0.3, 38.3 ± 0.3 and 38.5 ± 0.3 °C, respectively; post 30, 45, and 60: 37.8 ± 0.3, 38.1 ± 0.3 and 38.2 ± 0.4 °C, respectively). For WLFF, PSI was lower (p<0.05) at 15, 30, 45, and 60 min at post-season compared to pre-season (4.2 ± 0.7, 5.6 ± 0.9, 6.5 ± 0.9, and 7.1 ± 1.1 for 15, 30, 45, and 60 min pre-season, respectively; 3.6 ± 0.8, 4.9 ± 1.0, 5.7 ± 1.2, 6.3 ± 1.3 for 15, 30, 45, and 60 min post-season, respectively). For WLFF, RPE was lower during the post-season trial at 30, 45, and 60 min (pre 30, 45, and 60: 11.7 ± 1.4, 12.3 ± 1.2, and 13.5 ± 1.4, respectively; post 30, 45, and 60: 10.7 ± 1.2, 11.3 ± 1.3, and 11.9 ± 1.5, respectively), p<0.05. There were no differences between pre and post-season for the non-WLFF for Tc and PSI, but RPE was lower at 15 min during the pre-season trial. WLFFs demonstrated significant decreases in Tc, PSI, and RPE during controlled heat stress after the season. Since an age and fitness-matched control group experienced no indication of heat acclimatization, it is suggested that the long-term occupational heat exposure accrued by the WLFFs was adequate to incur heat acclimatization.
本研究旨在确定在为期 4 个月的野外火灾季节中，热适应的生理标志物的变化。在野外火灾季节（5 月至 9 月）前后，对 12 名野外消防员（WLFF）和 14 名非野外消防员（non-WLFF）进行了身体质量、体脂百分比和峰值 VO₂的评估。两组均在气候控制室内（43.3°C，33%RH）进行 60 分钟的热应激试验（以峰值 VO₂的 50%行走）。在试验过程中，测量了核心（Tc）和皮肤（Tsk）温度、心率（HR）、生理应激指数（PSI）和感知努力评分（RPE）。在野外火灾季节前后，WLFF 和非-WLFF 组之间的身体质量、体脂百分比或峰值 V.O2 没有差异。在 WLFF 直接参与野外火灾扑灭的 73 天中，WLFF 的每日高温高于非-WLFF，分别为 30.6°C 和 26.9°C，p<0.05。与野外火灾季节前相比，野外火灾季节后 Tc 较低（p<0.05），在 30、45 和 60 分钟时，分别为 37.9°C、38.3°C 和 38.5°C（野外火灾季节前分别为 37.9°C、38.3°C 和 38.5°C；野外火灾季节后分别为 37.8°C、38.1°C 和 38.2°C）。对于 WLFF，与野外火灾季节前相比，在 15、30、45 和 60 分钟时 PSI 较低（p<0.05）（分别为 15、30、45 和 60 分钟的野外火灾季节前分别为 4.2±0.7、5.6±0.9、6.5±0.9 和 7.1±1.1；分别为 3.6±0.8、4.9±1.0、5.7±1.2 和 6.3±1.3）。对于 WLFF，在野外火灾季节后，在 30、45 和 60 分钟时 RPE 较低（野外火灾季节前分别为 11.7±1.4、12.3±1.2 和 13.5±1.4；野外火灾季节后分别为 10.7±1.2、11.3±1.3 和 11.9±1.5），p<0.05。非 WLFF 在 Tc 和 PSI 方面，野外火灾季节前后无差异，但在野外火灾季节前的 15 分钟时 RPE 较低。WLFF 在季节后进行的受控热应激中，Tc、PSI 和 RPE 显著下降。由于年龄和健康状况匹配的对照组没有表现出热适应的迹象，因此，建议 WLFF 长期暴露于职业热环境中足以引起热适应。
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