The firefighter protective ensemble (PE), including Self-Contained Breathing Apparatus (SCBA), provides the wearer protection from hazardous environments, but increases physiological burden due to the additional weight and thermoregulatory challenges. User performance testing can be used to determine the level of physiological stress caused by the PE. PURPOSE: To examine the reproducibility of physiological variables in subjects performing repeated PE performance testing. METHODS: Ten healthy subjects (7 males and 3 females) participated in two repeated sessions of an exercise protocol involving treadmill exercise at 50% VO2max in an environmental chamber (22 degrees C, 50% relative humidity) while wearing a standard firefighter PE with SCBA. Physiological responses in measurements included core temperature (Tc), skin temperature (Tsk), heart rate (HR), sweat rate (SR), and performance time (PT). The measured variables were analyzed in terms of within-subjects and between-sessions by performing Pearson's correlations and paired samples t-test, respectively. RESULTS: All subjects completed two sessions while potential confounding variables such as hydration, circadian rhythms, etc were carefully controlled to be as identical as possible. The results showed that mean change (Delta) per min were: Tc: 0.021 (0.005), 0.021 (0.008) degree C, DeltaTsk: 0.113 (0.029), 0.116 (0.039) degree C, DeltaHR:2.9 (0.8), 3.0 (0.9), SR: 1.31 (0.52), 1.17 (0.38) kg/h, and PT: 28.8 (8.1), 28.5 (7.9) min, (session 1, 2) respectively. The measured variables found to be significantly highly correlated were Tc (r=0.649), Tsk (r=0.691), and HR (r=0.679). While there was no statistical difference in any variable analyzed for between-sessions, it was noted that a few subjects showed about 20-30% difference in PT between the two sessions. CONCLUSION: Physiological responses, as indexed by Tc, Tsk, and HR, in PE user performance testing were highly reproducible and variations in the measurements between the two repeated sessions were not statistically meaningful at the controlled experimental conditions. Factor(s) influencing the differences in PT observed in a few subjects was not clear, but elevation in body temperature did not seem to be responsible in the present study when considering Tc and Tsk.
Physiological-measurements; Fire-fighters; Fire-protection-equipment; Respirators; Personal-protective-equipment; Body-burden; Body-protection; Body-temperature; Weight-factors; Thermoregulation; Physiological-response; Physiological-stress; Physiological-testing; Humans; Men; Women; Performance-capability; Physical-exercise; Self-contained-breathing-apparatus; Heart-rate; Biological-monitoring
Jung-Hyun Kim, National Institute of Occupational Safety and Health, NPPTL, Pittsburgh, PA