Keep Your Cool: Wear Sunscreen

If you are thinking of running the Death Valley Century Race mid-August, but are afraid that sunscreen will make you retain heat, think again.

Researchers at the University of Vermont, Burlington, have found that wearing sunscreen doesn't impair the body's ability to dissipate heat.

The researchers were interested in studying the potential effects of water- and sweat-resistant sunscreens on the body's ability to dissipate heat. They theorized that the same properties that make these products resist water and sweat my also lead to decreased heat loss.

Twenty-two men underwent two 40-minute exercise tests, once with a full-body application of sunscreen and once without. Environmental conditions, clothing and workload were replicated during each individual's tests.

Mean skin temperature (MST), rectal temperature, oxygen consumption and heart rate during exercise were measured.

Only mean skin temperature appeared to be impacted by the introduction of sunscreen.

Initially, the application of sunscreen significantly reduced the mean skin temperature during exercise in the heat. But, according to researchers, this effect occurred in the first few minutes following application.

After that, MST values were similar in both treatment conditions.

Researchers could not determine a solid explanation for this effect, and suggest further study.

They did theorize that the enhanced cooling could be due to evaporative properties of alcohol and water contained in the sunscreen. Or, possibly, the same characteristics of the product that make them water resistant could lead to more moisture being trapped at the skin surface.

Source: Journal of Sports Medicine and Physical Fitness, March 2000; 40, 1, 35-40

This appeared in ACE FitnessMatters, ACE's official magazine.
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