Cue your favorite heat-related tune: maybe it’s Buster Poindexter’s “Hot, Hot, Hot,” Coolio’s “Too Hot” or Cole Porter’s inevitable “Too Darn Hot,” because it has been almost too darn hot to exercise outside in many areas lately. You might also include the Rio Olympics theme song. “It was very hot,” the women’s Olympic marathon champion Jemima Jelagat Sumgong of Kenya told reporters on Sunday after the 26-mile race, which featured withering temperatures in the 80s and drenching humidity.

In such conditions, many people choose to move their workouts into air-conditioned gyms. But whether out of necessity or by choice, others continue to exercise and compete outside.

For them, a new study of exercise in the heat could provide both relief and encouragement, because it suggests that one of the simplest, most low-tech ways to cool yourself during steamy workouts may also be the most effective.

I have written in the past about many different potential ways to help the body deal with summertime exertion, including freezing one’s underwear, slurping a slushie, wearing an ice-cooled vest, wrapping your neck with frozen cloths, or lying in a frigid water bath before beginning a workout.

In general, all of these methods have been found to help us to exercise for longer or at a more intense pace in the heat than if we make no formal effort to cool ourselves, although some work by different mechanisms than others.

Cold-water baths, for instance, lower the body’s internal, core temperature before exercise starts, a process known as precooling. Other methods cool the skin externally either before or during workouts. All can stave off the point at which our brains sternly direct us to slow down, find shade or stop altogether to avoid developing heat illness.

But there has been controversy among scientists and athletes about which of these techniques might be the most potent and also, importantly, practical.

So for the new study, which was published in June in the Journal of Sports Sciences, scientists at Southern Cross University in Australia and other institutions invited nine experienced male runners to the university’s exercise lab, which was heated to a baking 91 degrees.

There, each man was fitted with sensors that measured his core and skin temperature (at the forehead), heart rate and leg muscle activity, which indicates how hard the legs are able to work.

They then completed a five-kilometer time trial on a treadmill in the sweltering lab, without any type of cooling before or during the run, reporting to the researchers throughout the run how they felt.

A week or so later, each of the runners returned to the lab and repeated the entire procedure, but first they sat (mostly naked) in a bathtub filled with water chilled to about 73 or 74 degrees for 30 minutes.

Then, wearing the same sensors, they ran the five-kilometer time trial again. The room was as hot as before.

Finally, after another week or so, each runner returned to the lab one more time and ran yet another 5K, but this time a researcher sprayed the runner’s face every kilometer with cool water (chilled to about 72 or 73 degrees) from a spray bottle.

Then the researchers compared their times and other measures.

Cooling had definitely helped, the scientists found. The volunteers had run significantly farther and faster when they had cooled before or during the run than when they had not cooled at all, and these improvements were almost exactly the same with either cooling method.

The runners also had maintained more leg-muscle activation throughout the cooled runs, suggesting that their bodies had not become as fatigued. And subjectively, they said that they had felt less hot.

There were differences between the effects of the two cooling methods, though. The runners’ internal, core temperature was lowest before and during the run after they had lain in the chilly bath, whereas their skin temperature was slightly lower if they were cooled with water during the run.

But the performance differences between the two methods of cooling were negligible.

That outcome suggests that some type of cooling is going to help you to perform and feel better in hot conditions than no cooling, says Christopher Stevens, a professor of exercise science at Southern Cross University who led the study.

But if you don’t have the time or stomach for lengthy precooling in a chilly bathtub, then simply spritz yourself often in the face with a spray bottle, he says. Or “pour water over your head at every aid station” if you are racing.

However, it is important to remember that cooling will not necessarily prevent heat illness, he says. If you feel unwell, stop and seek shade. (Quite a few of the runners in the women’s marathon at Rio dropped out after overheating.) In addition, “wear light-colored, loose-fitting clothing and a hat,” Dr. Stevens says. “Drink to your thirst, and avoid wearing antiperspirant, which reduces sweating,” one of the key ways that the body disperses heat.

Source: The New York Times
August 17, 2016
By Gretchen Reynolds, photo by Doug Mills/The New York Times