By Lisa Rapaport

(Reuters Health) – Diabetes can make people more prone to heat stroke when they exercise on hot days, but two studies suggest there are things diabetics and others can do to lower their risk of heat-related illnesses.

Exercising in the heat may get harder with age because older adults don’t sweat as easily to help reduce body temperature. This risk may be even greater when people have diabetes because of diminished blood flow in the skin and reduced ability to get rid of excess heat by sweating, researchers note in JAMA.

One of the two studies published in the journal confirms that physically active people with diabetes sweat less, reach a higher body temperature and raise their heart rate more when exercising in the heat than counterparts without diabetes. But this study also found that one week of supervised exercise training in the heat could help diabetics sweat more and maintain a lower body temperature and heart rate.

“These findings are important because exercise is widely used to manage type 2 diabetes, and because there are many workers who have type 2 diabetes and are engaged in physically demanding jobs in hot environments,” said Glen Kenny, senior author of the study and a researcher at the University of Ottawa in Canada.

This study tested an exercise training program in 34 middle-aged and older men who typically got at least 150 minutes of moderate intensity physical activity a week, half of whom had diabetes. All of the participants completed exercise tests with three 30-minute bouts of cycling at increasing temperatures, once at the start of the study and again about a week later.

After the first exercise test, 10 men with diabetes and 8 men without the disease participated in a week-long exercise program to help them acclimate to exertion in the heat, doing 90 minutes of cycling a day in conditions similar to the exercise test.

In the second set of tests, people with diabetes who did the exercise training program improved their ability to shed body heat more than those without diabetes.

These results suggest that diabetics who are already physically active may benefit from doing a similar week-long program to prepare for workouts during the hot summer months, Kenny said by email. Even regular exercisers still need to be careful, however.

“Our study findings indicate that caution should be used when performing strenuous exercise especially in the heat,” Kenny said.

“Individuals should consider exercising indoors in a cool and or dry and well-ventilated environment if it is hot outdoors,” Kenny added. “When performing activities outdoors in the heat, try to limit the activities to the early or later hours of the day when temperatures are at their lowest.”

A separate study in JAMA offered another strategy to help diabetics manage exercise in the heat. This study found that wetting the skin with a cool sponge on the chest, arms, back, legs, and face may help reduce sweating and thermal discomfort during workouts in the heat.

Researchers tested three different cooling strategies for workouts in the heat: drinking cold water; soaking the feet and lower legs in cold water; and sponging cold water on the body. They tested these approaches in both humid and arid conditions in a group of young, healthy volunteers.

Soaking the feet lowered sweating and thermal discomfort only in hot, humid conditions; sponging cold water on the body reduced heart rate, sweating and thermal discomfort in both humid and dry conditions.

“Applying water to the skin enables it to evaporate, which takes with it quite a lot of thermal energy from the body,” said Ollie Jay, senior author of the study and director of the Thermal Ergonomics Laboratory at the University of Sydney in Australia.

“This is usually the job that sweating does, but this carries a physiological strain” that can lead to elevated heart rate, Jay said by email. “We also found that applying water to the skin also makes you feel cooler.”

SOURCE: and JAMA, online October 8, 2019.