According to a new study from scholars at the University of Connecticut, standard heat tolerance tests are not as effective at measuring tolerance in women compared to men.
Heat tolerance is a measure of how well someone tolerates exercise-heat stress. To test someone’s heat tolerance, researchers and practitioners use changes to heart rate and internal temperature over time to determine when the participant has become acclimated. These tests are often implemented in military and athletic populations to determine when it is safe for someone to return to duty or play following an exertional heat illness. However, even though they are used across the board for both men and women, heat tolerance tests were developed based on the male body, suggesting women may not be receiving accurate measurements of their tolerance.
For their study, the UConn research team used a heat tolerance test that is widely used for military and athletic assessments. It consists of walking on a treadmill for two hours at a temperature of 40 degrees Celsius (104 degrees Fahrenheit) with 40 percent humidity. By the test’s standard, a person is considered heat-tolerant if their core temperature stays below 38.5 degrees Celsius (101.3 degrees Fahrenheit) and their heart rate below 150 beats per minute for the duration of the test.
The research team found that women participants started the test at a higher temperature and heart rate, but they also stabilized at a higher temperature as they acclimated.
“The average for females is actually above that threshold,” said lead author Jacob Bowie, a postdoctoral fellow in kinesiology. “In the broader picture, when we don’t account for those sex-based differences, we could be limiting participation in military training or missions, or we could be tagging athletes as not ready to return to play, but they actually are.”