Heat acclimation benefits athletic performance in hot and cool conditions

Turning up the heat might be the best thing for athletes competing in cool weather, say human physiology researchers at the University of Oregon. Their paper, published in the October issue of the Journal of Applied Physiology, examined the impact of heat acclimation to improve athletic performance in hot and cool environments.

Researchers conducted exercise tests on 12 highly trained cyclists -- 10 males and two females -- before and after a 10-day heat acclimation program. Participants underwent physiological and performance tests under both hot and cool conditions. A separate control group of eight highly trained cyclists underwent testing and followed the same exercise regime in a cool environment.

The data concluded that heat acclimation exposure provided considerable ergogenic benefits in cool conditions, in addition to the expected performance benefits in the hot environment.

“Our findings could have significant impacts in the competitive sports world,” said Santiago Lorenzo, a researcher who performed the work as part of his dissertation at the University of Oregon. He is now completing post-doctoral training in the Institute for Exercise and Environmental Medicine (University of Texas Southwestern Medical Center) at Texas Health Presbyterian Hospital Dallas.

The study found performance increases of approximately 7 percent after 10 heat acclimation exposures.  “In terms of competitive cycling, 7 percent is a really big increase and could mean that cyclists could use this approach to improve their performance in cooler weather conditions,” said Lorenzo. However, the heat exposures must be in addition to the athletes’ normal training regimen.

Heat acclimation improves the body’s ability to control body temperature, improves sweating and increases blood flow through the skin, and expands blood volume allowing the heart to pump more blood to muscles, organs and the skin as needed.

The study was conducted in the UO's Evonuk Environmental Physiology Core lab. The climatic chamber was set at 38 degrees Celsius (100 degrees Fahrenheit) for heat testing and 13 degrees Celsius (55 degrees Fahrenheit) for cool conditions with consistent humidity (30 percent relative humidity) for the cyclists’ exercise tests.

Lab co-director and study co-author Christopher Minson said that the heat may produce changes in the exercising muscle, including enzymatic changes that could improve the amount of work done by the muscle, but he says future research will have to examine it further. “A next step is to determine whether heat acclimation improves performance in a competitive or real-world setting.”

News of the findings spread quickly, covered by HealthDay, U.S. News & World Report, Business Week and The New York Times, to name a few. Minson and Lorenzo also appeared together for a 30-minute live interview session on the Jefferson Exchange, an NPR-affiilate show out of Ashland and heard throughout Oregon and northern California.

Here's a related video about the UO's environmental chamber.