Defence R&D Canada-Toronto, Toronto, Ontario, Canada.
Compr Physiol. 2013 Jul;3(3):1363-91. doi: 10.1002/cphy.c130002.
In many occupational settings, clothing must be worn to protect individuals from hazards in their work environment. However, personal protective clothing (PPC) restricts heat exchange with the environment due to high thermal resistance and low water vapor permeability. As a consequence, individuals who wear PPC often work in uncompensable heat stress conditions where body heat storage continues to rise and the risk of heat injury is greatly enhanced. Tolerance time while wearing PPC is influenced by three factors: (i) initial core temperature (Tc), affected by heat acclimation, precooling, hydration, aerobic fitness, circadian rhythm, and menstrual cycle (ii) Tc tolerated at exhaustion, influenced by state of encapsulation, hydration, and aerobic fitness; and (iii) the rate of increase in Tc from beginning to end of the heat-stress exposure, which is dependent on the clothing characteristics, thermal environment, work rate, and individual factors like body composition and economy of movement. Methods to reduce heat strain in PPC include increasing clothing permeability for air, adjusting pacing strategy, including work/rest schedules, physical training, and cooling interventions, although the additional weight and bulk of some personal cooling systems offset their intended advantage. Individuals with low body fatness who perform regular aerobic exercise have tolerance times in PPC that exceed those of their sedentary counterparts by as much as 100% due to lower resting Tc, the higher Tc tolerated at exhaustion and a slower increase in Tc during exercise. However, questions remain about the importance of activity levels, exercise intensity, cold water ingestion, and plasma volume expansion for thermotolerance.
在许多职业环境中，人们必须穿着防护服来保护自己免受工作环境中的危害。然而，个人防护服（PPC）由于高热阻和低水蒸气透过率，限制了与环境的热交换。因此，穿着 PPC 的人经常在无法补偿的热应激条件下工作，身体热量不断积累，热损伤的风险大大增加。穿着 PPC 时的耐受时间受三个因素影响：（i）初始核心温度（Tc），受热适应、预冷、水合、有氧健身、昼夜节律和月经周期的影响；（ii）Tc 在衰竭时的耐受能力，受封装状态、水合和有氧健身的影响；（iii）Tc 从热应激暴露开始到结束的增加率，取决于服装特性、热环境、工作强度以及个体因素，如身体成分和运动经济性。减少 PPC 中热应激的方法包括增加空气透过性的服装、调整 pacing 策略，包括工作/休息时间表、身体训练和冷却干预，尽管一些个人冷却系统的额外重量和体积抵消了它们的预期优势。由于较低的静息 Tc、在衰竭时可耐受的更高 Tc 以及在运动过程中 Tc 增加较慢，经常进行有氧运动的低体脂个体的耐受时间比久坐不动的个体长 100%。然而，关于活动水平、运动强度、冷水摄入和血浆容量扩张对耐热性的重要性仍存在疑问。
