Physiological Impacts of Cold Conditions during Moderate Intensity Activity while Wearing Firefighter Protective...

Thermal protective clothing (TPC) protects firefighters from physical threats associated with structural firefighting. However, it also limits the release of body heat generated, which can result in hyperthermia and dehydration. Despite the prevalence of winter structure fires in the United States, there is a paucity of cold-weather firefighting research.

This study documented physiological responses to moderate-intensity exercise in a cold environment while wearing TPC with the hypothesis that while exercising in firefighting TPC, a cold environment would maintain normal core body temperature and decrease extremity temperature compared to a thermal neutral environment.

Fourteen firefighters (two females; 30.9 [SD = 8.1] years) participated in both a thermal neutral (20°C) and cold (-8°C) condition simulation. Each subject was outfitted with a heart rate (HR) monitor, eight surface temperature sensors, and a core temperature (Tc) capsule prior to donning TPC. For each condition, subjects walked on a treadmill in an environmental chamber to simulate the common firefighting work intervals of two 20-minute sessions, with a short rest in between, followed by a 20-minute rehabilitation period. Body temperatures, HR, respiratory rate (RR), rate of perceived exertion (RPE), and thermal sensation, comfort, and preference were recorded during exercise and recovery.

Core temperature, HR, RR, and RPE increased during exercise in both conditions. Mean skin temperature (MST) rose during the thermal neutral condition but not during the cold condition. Overall, Tc (0.3 [SD = 0.4]°C; P = .0142), HR (26.3 [SD = 8.36] BPM), RR (3.56 [SD = 5.6] BPM), RPE (2.0 [SD = 1.9]), and MST (3.4 [SD = 1.2]°C) were all higher at the end of the neutral condition compared to the cold condition. During recovery, most measures returned to baseline after approximately five-to-20 minutes in both conditions, but they recovered more slowly in the thermal neutral condition.

Moderate-intensity exercise in TPC increased physiological and perceptual measures more in a thermal neutral environment than a cold environment. Recovery was faster following the cold condition. This may allow firefighters to work for longer durations or recover faster, possibly allowing for fewer crews on scene. However, this study did not account for the risk of other cold induced conditions due to prolonged exposure, such as frostbite. Further investigations should be conducted on cold weather firefighting and its impact on firefighters to establish guidelines and standard operating procedures.