The Olympians streaming into Tokyo this week are about to be faced with the hottest games in decades, with temperatures around 90 degrees Fahrenheit and suffocating humidity. Many athletes and sports physiologists have had their eye on the summer temperatures in Japan for years and have been planning to help athletes acclimate to the heat. 

In the weeks leading up to the games, female Olympians may have had to spend more time preparing for the heat than their male counterparts. Some early studies show that it can take twice as long for female athletes to adjust than male athletes. The information is limited, though, because until only a few years ago, most of the research on how to prepare to compete in hot environments was only done on male athletes. 

“There are going to be more considerations to make for female athletes, and there are definitely some differences in how they adapt,” says Jessica Mee, who studies performance in extreme environments at the University of Worcester in the United Kingdom.

Athletes can use a number of strategies to acclimate to the heat, like training in layers of clothing, doing extra training sessions to keep the body temperature elevated, or spending time in heat chambers or saunas after exercising. The process lets the body disperse heat more easily, decreases core temperature and resting heart rate, and increases sweat rate — all of which let someone perform at a high level even in hot temperatures. The changes can last around a week after someone leaves a hot environment before starting to drop back to normal. 

Most research outlining this process, though, was done on male athletes. “For so long the narrative has been about young, healthy men,” says Oliver Gibson, who studies physiological responses to heat at Brunel University London. “We’re only now just getting down to the details of sex differences in heat responses.” It’s a common problem in sports medicine: female athletes are highly underrepresented in sports science research, so most of our understanding about how the body responds to exercise and under various conditions is based on male athletes.

Over the past few years, a few studies by Gibson, Mee, and others helped sketch an initial understanding of the differences between how male and female athletes respond to the heat. They both seem to react to being in hot environments in similar ways, Mee says. The differences crop up around preparation to be in hot environments. Her research and other studies show that it takes longer for female athletes to adapt to being in the heat than it does male athletes.

In general, male athletes could adjust in around five days of heat acclimation, but it took female athletes 10 days, Mee’s study found. “For females, it’s going to take more than this short-term five day approach that is usually seen as preferable because it’s less compromising on their training,” she says. “They have to make sure that they’re getting adequate time to implement these strategies.”

It’s not clear why it takes female athletes longer to acclimate, Gibson says. It may be that, because males tend to have more muscle mass (which heats up more quickly), they’re able to get their body to adapt to the heat more quickly. Larger male bodies might also store more heat, so they get to that point sooner. 

Gibson says he’s had conversations about heat acclimation for athletes with the English Institute of Sport, which supports British Olympians, over the past few years. That’s included conversations about the sex differences in heat acclimation. “From the outset, we’ve said that for female athletes, you need to consider this additional time burden,” he says. “It’s certainly something that I know that, within the UK at least, has been on the mind of those who are preparing.”

The Great Britain women’s soccer team worked with the English Institute of Sport on its heat acclimation programs, which included spending 90 minutes a day on a stationary bike in a heated, humid tent for a week, The Athletic reported. Other countries are implementing similar programs: the Canadian women’s eight rowing team trained in a heated sports dome, according to CBC, and United States athletes got custom acclimation programs from the US Olympic and Paralympic Committee’s senior sports physiologist Randy Wilber. 

“Athletes who prepare effectively for heat and humidity can beat a lot of athletes who have more talent than they do but who have not prepared effectively for heat and humidity,” Wilber told The Washington Post. 

Understanding the differences between how male and female athletes acclimate can help elite athletes preparing for the Olympics. But they also have implications outside of sports. Climate change is making the hottest days hotter around the world, and record-shattering heatwaves are occurring with steady frequency. Extreme heat is a dangerous health risk, and figuring out how to help people adapt to hot temperatures is an important public health issue. 

Heatwaves are a particular risk to people who work outside, like farmworkers. Male workers might adapt to the heat in a few days, but it could take female workers longer. Recommendations around how people should adjust to and protect themselves from the heat should be tailored to each individual, Gibson says. “If we’re saying that for four or five days you should reduce your activity and then you’ll be able to gradually return to activity levels before the heat wave, for females, it might be four or five days is insufficient,” he says. They might need more heat protection because their bodies may not adjust over the course of a few-day-long heatwave. 

Athletes tend to be the starting point for a lot of research on physiology because there’s a clear application for what they learn, Mee says. “There’s a drive and interest in getting additional marginal gains,” she says. They’re also often a healthy and robust group, and they can handle the type of stressors researchers need to put on the body to learn how it responds, Gibson says. Then, experts can take that information and see what might also apply to everyone else. “While what works for an athlete might not work directly for a member of the general public, we can learn some lessons there,” he says.