Cardiorespiratory and thermoregulatory response of working in fire-fighter protective clothing in a temperate environment
The cardiorespiratory and thermal responses of two intensities of treadmill exercise were compared for brief periods (12 min) in fire ensemble (FE) but without self contained breathing apparatus, and sports ensemble (SE), in a temperature environment. A further experiment explored the responses of subjects exercising in FE over a prolonged period (60 min). Eighteen male firefighters wearing either FE or SE walked on a level treadmill for 6 min at 5 km.h-1 increasing to 7 km.h-1 for 6 min. Following a recovery interval of 1 h, the exercise protocol was repeated in the second ensemble; the order of ensemble was balanced. Heart rate (HR), rectal temperature (Tre), V ˙O max and rating of 2 perceived exertion (RPE) were monitored continuously under both ensembles. At 7 km.h-1, V ˙O was significantly higher (p < 0.05) in FE (36.1 and 39.9 ml.kg-1.min-1) than in SE and represented 74% V ˙O max. There were no changes Tre. In experiment 2, following a rest interval of2 at least 36 h, eight subjects in FE walked on the treadmill at 6 km.h-1 (gradient 10%) for 60 min also in temperate conditions, where HR, T re and RPE were recorded at 10-min intervals. During the 60-min exercise in FE, HR reached 161 beats.min-1 and T re increased to 38.3°C. Despite considerable subject discomfort, Tre remained below dangerous levels (38.4°C). When RPE were compared with a physiological strain index (PSI) calculated from Tre and HR data over 60 min, there was no significant difference (p < 0.05) with a correlation coefficient (r) of 0.98. The results suggest that RPE and PSI are closely related when exercise is sufficiently prolonged or intense to elevate Tre and HR in fire-fighters wearing FE in temperate conditions. If further investigation confirms this relationship for hot humid conditions in which fire-fighters operate, then with training, it may provide individuals with a valid measure of dangerous levels of perceived heat strain.
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Document Type: Research Article
Affiliations: School of Sport Health and Exercise Sciences, University of Wales-Bangor, Bangor LL57 2EN, UK
Publication date: September 1, 2000