This is an area of science called thermoregulation and is typically in the exercise physiology departments of Universities. What has been established so far in the research is a correlation between an increase in core temperature and the onset of fatigue. Researchers have looked at the effect of drinking hot versus cold liquids on core temperature and have found, although not to surprising, that hot liquids increased while cold water decreased core temperature.
The next question is does this have an affect on exercise performance?
Well, researchers from Loughborough University in the UK looked at if drinking water temperature has an affect on exercise performance. In this research they used a cycling protocol to exhaustion in an environmentally controlled chamber with an air temperature of 35 degrees Celsius and 60% relative humidity. The cold water was at a temperature of 4 degrees Celsius (typical temperature of a fridge) while the warm water was at 37 degrees Celsius (body temperature). Each subject performed the test protocol with each drink temperature on separate occasions.
Conclusion of the study, drinking cold water improves performance (by around 20% per subject with some as high as 34%) when compared to warm water. Please keep in mind that the cycling test was an endurance event lasting around 50-60 minutes so the results probably have little affect for sports which are shorter in duration (e.g. 100m sprint, weightlifting, shot put, discus ...).
But for two sports I cover often here, Water Polo and Basketball, I think this research is very applicable. For the Water Polo players out there who have had to train or play a match in a very warm pool will note how quickly fatigue sets in when compared to a cold pool (i.e. core temperature goes through the roof and you get hot very quickly) or for everyone else how tired you feel after being in a hot tub or sauna. Drinking cold water could certainly have a positive effect by limiting how high your core temperature rises.
Bottom line, drink cold water when exercising, especially when training in hot humid environments.
Gisolfi CV, Copping JR. Thermal effects of prolonged treadmill exercise in the heat. Med Sci Sports. 1974;6:108–13.
Gonzalez-Alonso J, Teller C, Andersen SL, Jensen FB, Hyldig T, Nielsen B. Influence of body temperature on the development of fatigue during prolonged exercise in the heat. J Appl Physiol.
Lee JKW, Shirreffs SM & Maughan RJ. Cold Drink Ingestion Improves Exercise Endurance Capacity in the Heat. Med. Sci. Sports Exerc., Vol. 40, No. 9, pp. 1637–1644, 2008.
I would like to thank the Youth Basketball Medicine Blog for initially making me aware of this research and furthering my study into this area of thermoregulation.