Van Rensburg, J. P., Kielblock, A. J., & Schutte, P. C. (1984). Heat acclimatization as a method of improving sporting prowess. South African Journal for Research in Sport, Physical Education and Recreation, 7(2), 17-30.
Trained rugby players (N = 15) were subjected to a heat acclimatization program that exceeded the level of heat that would be experience in a competitive setting. In the acclimatization process, temperatures and heart rates decreased significantly while sweating increased slightly (these are all signs of adaptation to heat stress). These changes did not extend to simulated playing conditions. Since the rugby players were aerobically trained, one of its adaptations being making work in the heat easier, it is possible that the difference between the original and test conditions were small enough to be accommodated by the endurance training effects alone. The exact changes that were demonstrated in the very hot conditions were specific to the environmental conditions, and the duration, rate, and type of work. The "over-acclimatized" state yielded no additional benefits to the athletes.
Implications. Heat is yet another specifically-trained function when the expected conditions are very markedly different to normal. However, when athletes are endurance trained and the heat conditions are only slightly hotter than normal, it is likely that the extra stress can be accommodated by the extra benefits of endurance training (principally that of a more efficient circulation and sweating response).
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