With extreme heat a growing challenge for summer sport, University of Sydney researchers are working with Tennis Australia to develop evidence-based tools to keep players safe at the Australian Open – and to help everyone better manage extreme heat when playing sport.
January in Melbourne is synonymous with tennis – and heat.
“The Australian Open is held in the hottest month of the year,” says Carolyn Broderick, Chief Medical Officer at Tennis Australia. “My job is to ensure players are healthy and safe on the court.”
According to Professor Ollie Jay, Director of the University of Sydney’s Heat and Health Research Centre (HHRC), 2024 was the hottest year on record. Globally, the average person experienced an extra 16 days of dangerous heat, alongside a record number of 20 heatwave days.
Understanding how heat affects the body – and how to manage it – sits at the heart of the HHRC’s work. Their research spans public health, community sport and elite competition, with the Australian Open one example of science in action.
“What heat does is place enormous strain on the body,” Ollie explains. “As core temperature rises, the heart has to work harder, blood pressure can drop, kidneys come under stress, and if someone can’t cool down, the consequences can be serious.”
That risk is amplified for athletes pushing their bodies to the limit.
“So, we need ways of monitoring heat and providing clear strategies for dealing with heat stress,” Ollie says.
That’s where the Environmental Measurement Unit (or EMU as it is affectionately known as) comes in.
“The EMU was developed by the Heat and Health Research Centre as a way of measuring the environmental conditions during our field studies,” says Megan Tiong, an exercise physiologist and PhD candidate at the HHRC.
“It measures four key environmental factors – air, temperature, humidity, radiant heat of the sun and wind speed in real time.”
There are presently five EMU across the Australian Open tournament grounds at Melbourne Park.
“We have five of them at the Australian Open,” Carolyn says, “just to reflect the different conditions that we have around the site, and they are monitoring continuously throughout the competition. That data feeds directly into our decision-making.”
It takes the guesswork out of extreme heat.
Director, Heat and Health Research Centre
The information from the EMUs underpins the Australian Open Heat Stress Scale – a simple, five-point system developed by Tennis Australia in collaboration with University of Sydney researchers.
“The scale is evidence-based and easy to understand,” Carolyn says. “At each level, we know exactly what action to take – whether that’s additional cooling strategies, extended breaks, or stopping play altogether.”
At higher levels of heat stress, mandatory breaks are introduced between sets. At the most extreme level, outdoor matches are suspended, and roofs are closed on indoor courts.
“Fortunately, we’ve had no cases of heat stroke at the Australian Open,” Carolyn says. “But we do see milder heat-related illness like headaches, dizziness and nausea. This system has helped us reduce incidents and feel confident that player safety comes first.”
While the Australian Open may be one high-profile application of the HHRC team’s research, it has much broader relevance.
“Heat stress can affect everyone differently and have different risks for each person,” says Megan. “In Australia, we all live in extreme heat during the summer, so it affects everyone.
“Heat stress just makes your perceived effort more, so you’re not able to push yourself to your limit as much, which can also be a protective mechanism in keeping yourself safe in heat.”
Inside the HHRC’s climate chambers, researchers recreate heatwave conditions with precise control over temperature and humidity. This allows participants to test different cooling strategies and helps the team identify what really works.
“Our climate chamber can mimic different heatwaves and settings you might experience when you’re playing sport and allowing us to test different populations and cooling strategies,” Megan says.
The HHRC’s work has already influenced heat-health guidelines across Australia and internationally, including adoption by the World Health Organization. Tools developed with sporting bodies are now also being used by other codes, from cricket to rugby, and adapted for community sport.
“Every sport should have an extreme heat policy,” Carolyn says. “And these tools can help everyday Australians make safer decisions too.
“At the heart of everything we do in player medical at the Australian Open is player safety and health and I think this system has enabled us to feel confident the in the area of extreme heat, we’re doing just that.”