Extreme Heat Poses Growing Risk to Athletes Globally

The death of Fijian rugby player Saimoni Vunilagi in Japan underscores the growing threat of heatstroke in sports, particularly as extreme heat events become more frequent worldwide. Vunilagi, 26, fell ill during a training session with his team, Kyuden Voltex, in Fukuoka on August 3rd. The club stated he displayed symptoms consistent with severe heatstroke. Despite medical efforts, he passed away a few days later. The incident occurred during a period of intense heat in Japan, with temperatures reaching 35C (95F) by noon on the day Vunilagi became ill, coupled with over 75% humidity.

This event casts a spotlight on the risks athletes face in high temperatures. Similar incidents have been reported globally. Tennis players Jakub Mensik and Ekaterina Alexandrova collapsed during matches played above 30C (86F), and eight runners required hospitalization during a marathon in South Korea in April when temperatures hit 29C (84.2F). Cyclist Tadej Pogacar described the heat during this year's Tour de France as "dangerous," while Matthew Brennan questioned the safety measures after temperatures exceeded 40C (104F) during the Vuelta a Espana.

Many sports governing bodies, including those in tennis, athletics, and cycling, utilize the Wet Bulb Globe Temperature (WBGT) to assess heat stress. This metric considers air temperature, humidity, wind speed, sun angle, and solar radiation. However, experts argue that more standardized and robust protections are needed across all sports to mitigate the rising risk of heat-related fatalities.

"We have seen an increase in the number of heat illness events in rugby and many other sports around the world in recent years," said Dr. Madeleine Orr, assistant professor of sport ecology at the University of Toronto. "People assume we've seen such extreme heat before and think, 'it was fine, we pushed through, we can do it again'. That's not necessarily true – the heatwaves we're experiencing today are hotter than the ones in your childhood, because heatwaves are relative to the local normal, and 'normal' levels have risen."

Calls are growing for universal policies that provide clear guidelines for athlete safety during extreme heat. "Different leagues have different policies – there needs to be more of a standardized approach so that everyone just knows what to do," Orr stated. "It's similar to lightning – most people are familiar with the idea that when there's lightning near a sports event, we take a break for 30 minutes and start once it has gone away. We need a similar policy on heat and we need it to apply everywhere."

Convincing athletes and coaches to prioritize health over performance in extreme conditions presents a significant challenge. Christian Day, general secretary of the Rugby Players' Association, noted that "a lot of coaches think that heat regulation is a hindrance." He emphasized the need for athletes to be protected from pushing themselves too hard, stating, "Players need protecting from themselves sometimes." Day advocates for regulatory thresholds that trigger automatic stops in play or training, regardless of athlete or coach inclination.

World Rugby updated its heat and air-quality guidelines in 2025, introducing a heat stress index from 0 to 250. While this allows for measures like water breaks and extended half-time periods at lower danger levels, it also permits the suspension or postponement of matches at higher levels. However, Day pointed out that athletes spend significantly more time training than competing, highlighting the need for stricter regulations during training sessions.

"If this level of heat is going to become the norm, then we need central regulation and governance as to how we help clubs manage their players and how they should react to these kind of temperatures," Day said. "Maybe there are cases where perhaps training needs to be limited in time, or doesn't take place at all that day outdoors."

Pre-season training is often a particularly vulnerable period for athletes. The Japan Rugby Football Union (JRFU) issued a warning to clubs on June 5, 2026, emphasizing heatstroke as an increasing concern during the summer and urging that safety be the top priority for summer training camps.

Heatstroke is a critical condition where the body's temperature regulation fails, leading to organ damage and potentially death within a short period. Symptoms include dizziness, nausea, headache, and confusion. "Heatstroke is 100% preventable, so every single death is one too many," Orr asserted. She clarified that fitness does not confer immunity to heatstroke and noted that larger bodies, which generate more heat, can be more vulnerable. "So while yes, professional athletes are extraordinarily fit, that doesn't save them when the issue of concern is cooling off the body."

The risks extend beyond elite athletes to those participating at grassroots levels. "Whatever the elite level does, we'll see it trickle down into grassroots," Day observed. "And that's why it's crucial that the elite level of every sport sets the right example because the kids, the players of tomorrow, will absolutely copy whatever they see their heroes doing."