• Physiological and Perceived Effects of Head Cooling During Simulated Firefighting Activity

      McKenzie, Amy L. (2011-07-19)
      Accessory cooling devices have been developed to protect firefighters (FF) from suffering an exertional heat illness by attenuating the rise in core body temperature. Head cooling (HC) via a cold gel pack placed inside the helmet is one cooling mechanism marketed to FF, but the research regarding its efficacy is limited. PURPOSE: To investigate the physiological and perceived effects of HC during simulated firefighting activity (FFA). METHODS: Participants (males; 40±8 y; 168±7 cm; 91.8±14.2 kg) were randomly assigned to either the HC group (n=9), who completed FFA while wearing a cold gel pack inside their helmet, or the control (CON) group (n=10), who received no accessory cooling during FFA. FF completed four FFA stations in full turnout gear and self-contained breathing apparatus (SCBA) (23.3±1.4 kg). FFA stations lasted 15 min and included an obstacle course, a high-rise drill, a two-story search and rescue drill, and car extrication. Stations were completed in random order. After each station, FF replaced their air cylinder and HC replaced their gel pack; FF then completed a different station. After every two stations, the FF rested for 15 min in the shade by removing their turnout gear and SCBA and drinking water ad libitum. Gastrointestinal temperature (GI), heart rate (HR), Stroop Test interference score (ST), rating of perceived exertion (RPE), perceived thermal strain (PTS), and hydration status were measured. Repeated measures ANOVAs were used to compare groups across time. RESULTS: No significant demographic differences were found between groups (p>0.05). GI (39.18±0.49°C) and HR (163±22bpm) increased during FFA. No significant interactions were found for GI, HR, ST, PTS, or RPE (p>0.05). There were no differences in sweat loss (2.5±0.8 L), hypohydration (0.9±0.8%), or post FFA urine specific gravity (1.020±0.008) between groups (p>0.05). Weak relationships were noted between perceived thermal sensation and gastrointestinal temperature (r=.248). CONCLUSION: HC did not attenuate the rise in GI or reduce HR during FFA. The discrepancy between perception and actual body temperature may be dangerous for FF, as it may allow them to work beyond their central drive and the critical GI threshold.