Effects of Highly Concentrated Artificial Carbonic Acid Forearm-Bathing on Core Temperature Cooling for Hyperthermia

Abstract

PURPOSE: High temperature and high humidity make heat radiation inefficient, it is easy to suffer from hyperthermia during exercise. This study examined the effect of cooling by the highly concentrated artificial carbonic acid water at rest following exercise. METHODS: Subjects were nine male students who consented to participate in the present study. Subjects were not permitted to consume alcohol on the day before the test, engage in exercise on the day of the test, or eat during the 2 hours prior to the start of the test. After 60 min resting state in a controlled environment (room temperature, 29°C; relative humidity, 70%), they exercised by cycle ergometer at 75%HRmax for 20 minutes. Then the subjects were cooled using each of the following methods: immersion of both arms in highly concentrated artificial carbonic acid water (33°C), and immersion of both arms in tap water (33°C). The skin (forearm) and core (sub-lingual) temperatures and thermal sensation in the forearm and body were measured. RESULTS: The sum of core temperatures decreases to the experiment end, assuming the time of immersion start as standard, and was larger with the carbonic acid water (13.0 ± 0.99°C) than with the tap water (12.6 ± 1.89°C). However, there was no significant difference between the immersion trial comparisons. The skin temperature decreases with the carbonic acid water (1.55 ± 0.09°C) were significantly smaller than that with the tap water (1.91 ± 0.10°C). And at the time of immersion, each of the between immersion trial comparisons was significantly different in thermal sensation for the forearm. The subjects felt warmer with the carbonic acid water (5.94 ± 0.21) than that with the tap water (4.45 ± 0.18). CONCLUSION: The carbonic acid water was larger in the sum of the variation of decline of core temperature. These data indicated that carbonic acid attenuated skin vasoconstriction and suppressed the drop in blood flow compared to water. As a result carbonic acid decreased core temperature efficiently. These results suggest that forearm bathing in highly concentrated artificial carbonic acid might afford cooling efficiency without placing athletes under the burden of cold water stimulation.