July 14, 2006

“Precooling” before exercise helps beat the heat

NEW YORK (Reuters Health) - 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

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.