Observational Study of Lactate Accumulation and Recovery During Simulated Fire Suppression Activities and Orthostatic Tolerance During Recovery
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The health and safety of firefighters is of the upmost importance yet there is inadequate information regarding the full extent that the physical demands and stressors of firefighting have on firefighters. Therefore, the purpose of this study was to examine aspects of physiological strain and recovery on a firefighter physical skills test in the heat. Eleven healthy male and female subjects with an average age of 22 ± 2 years, and a maximum oxygen uptake (VO2max) of 46.1 ± 5.5 ml/min/kg (mean ± SD) completed the study. Whole body aerobic capacity, upper body aerobic capacity, upper- and lower-body strength, muscular endurance, anaerobic power, body composition, and baseline cardiovascular response to an orthostatic challenge were assessed to determine physiological characteristics of the subjects prior to the experiment. To quantify firefighting performance, a four-event test battery was administered in an uncompensable environment (40ºC and 60% relative humidity). For the control visit subjects wore standard work pants, boots, t-shirt, and Velcro belt. For the experimental visit, subjects wore full thermal protective clothing and breathing protection that weighed approximately 20 kg. Following the protocol in the heat subjects submitted to a head-up tilt test for 45 minutes or until they displayed signs of presyncope. Wearing protective clothing while performing fire suppression in the heat resulted in a significant difference in most physiological responses. Core temperatures (p = 0.03), heart rate (p < 0.001), lactate (p < 0.001), and sweat rate (p < 0.0001), were higher when wearing thermal protective clothing. When subjects were divided based on in to high and low performance groups based on whether they reached 90% of their maximum heart rate in under ten minutes (low performers) or over ten minutes (high performers), there were no significant differences between high and low performers; however, differences in cardiovascular responses trended toward significance. Additionally, there were no fitness parameters that accurately predicted performance in the heat, and there were no significant differences in performance on the fitness parameters between performance groups. Finally, work in protective garments changed heart rate and blood pressure during a head-up tilt test; though, these differences did not affect the time to presyncope.