Evaluation of post-cooling techniques to treat hyperthermia
Conference Contribution ResearchOnline@JCUAbstract
Introduction: For the treatment of exercise-induced hyperthermia, iced- or cold-water immersion has been reported as the most effective cooling technique although, suitable facilities may not be always available in field environments. Subsequently, it was the aim of the current study to evaluate and compare the efficacy of three field based, post-exercise cooling techniques (infusion of fridge-cold saline, strategically placed ice packs, and simultaneous fan cooling with intermittent water spraying) for the treatment of exercise-induced hyperthermia. Methods: Eleven healthy, active males volunteered to participate in three trials, separated by 72-96 hrs, and provided written informed consent. All testing procedures were conducted within a climate control chamber (34.2 ± O.5°C, 62.3 ± 3.1% RH and circulating airspeed ≤ 0.5 ms-1) and were approved by both the Australian Defence Human Research Ethics Committee and James Cook University Human Research Ethics Committee. Each participant completed three trials in a balanced order. Participants were heated to a core body temperature (Te) of 40.0°C by an intermittent walking/running protocol (2 min at 6 kmh-1 and 4 min at 10 kmh-1) followed by one of three treatment (cooling) techniques: intravenous saline infusion (IV), ice packs (ICE) applied to the groin, axillae and back of the neck; or water spray and fan cooling (FAN). Following a 5-min transition phase, participants commenced the 40-min supine treatment phase with Tc, mean skin temperature (TSK) and heart rate (HR) recorded every minute. Data were analysed via 2-way repeated measures ANOVA (treatment x time) and Tukey's post-hoc tests with alpha set at 0.05. Results: The Tc at the commencement and end of the 40-min cooling period was equivalent between trials. However, the rate of reduction in Tc during the first 20 min of treatment was significantly greater for FAN compared to ICE (0.09 ± 0.02°C vs 0.07 ± 0.02°C; p<0.05), with IV not differing to FAN or ICE (0.08 ± 0.01°C; p>0.05). A main effect for TSK was exhibited with significantly lower values for FAN (33.5 ± 1.4°C; p < 0.05) compared with both IV (36.6 ± O.7°C) and ICE (36.6 ± 0.6°C). Sweat rates during the treatment period were significantly greater for IV (1.1 ±0.5 Lh-1) compared to both ICE (0.6 ± 0.3 Lhr-1; p < 0.05) and FAN (0.2 ± 0.2 Lh-1; p < 0.01). During treatment, HR was significantly reduced from exercise values and significantly lower for FAN compared with IV (5-40mins post-exercise). Discussion/Conclusion: It would seem that the ICE and FAN treatments reduced, while the IV treatment preserved, thermoeffector responses, yet T c was equivalent after 40 min of cooling. Considering the large suppression in sweat rate in the FAN trial, it is extremely important that the skin is regularly wetted to facilitate evaporation, otherwise evaporative heat loss would cease once the skin was dry and TSK was less than environmental temperature. Overall, all three techniques were effective in reducing Tc and it is predicted that if these techniques were used simultaneously greater rates of reduction in Tc would be expected.
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3rd Australian Association for Exercise and Sports Science Conference and the 5th Sports Dietitians Australia Update
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978-0-646-48582-9
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1
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Melbourne, VIC, Australia
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Australian Association for Exercise and Sports Science
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Melbourne, VIC, Australia
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