Cooling down before warming up may help exercisers keep going during the dog days of summer, according to a small study.

Researchers found that when they outfitted male cyclists with special "precooling" garments before a workout in the heat and humidity, the athletes showed cooler body temperatures, lower heart rates and less sweating.

The cool down came courtesy of shirts and pants with tubing that allowed cold water to run through the clothes. Other studies have shown that a pre-workout dip in a cold bath or exposure to cold air can help exercisers lower their odds of heat strain in hot, humid weather.

Dr. Hein Daanen of the research institute TNO in the Netherlands led this latest study, published in the International Journal of Sports Medicine.

Physical activity causes the body's core temperature to rise, with hot, humid weather spurring a particularly rapid ascent; at a certain point, an exerciser must slow down or risk heat-related illness. The idea of precooling is to increase the body's heat tolerance by starting exercise with as cool a body temperature as possible.

The current study included eight male cyclists who were asked to ride in summer-like heat under each of four conditions: after precooling just the upper body; after cooling the lower body only; after a whole-body cool down; and after no precooling.

Compared with the cooling-free ride, Daanen's team found, the cyclists had fewer signs of heat strain during their post-cooling rides. Also, contrary to the researchers' expectations, precooling the leg muscles did not diminish the athletes' performance, despite the fact that it's generally considered a bad idea to work "cold" muscles.

Therefore, the researchers conclude, "it seems to be of no importance" which body parts an athlete chooses to chill before heading out into the heat.

SOURCE: International Journal of Sports Medicine, May 2006.