'Tragic but avoidable' — heat-related risks in sport after death of Saimoni Vunilagi

On Monday, 3 August, Fijian rugby player Saimoni Vunilagi set off from home to train with his team‑mates in Fukuoka; after the session he was taken to hospital and a few days later the 26‑year‑old was dead. Kyuden Voltex, the Japanese second division club for which he was training, said he "displayed symptoms consistent with severe heatstroke" and added "despite the best efforts of the medical team, he sadly passed away".

The Met Office has confirmed that 2026 was the UK's hottest summer, and many other countries around the world have also dealt with extreme heat; Japan, like the UK and Europe, experienced severe heatwaves this summer. By noon on the day Vunilagi became ill, the temperature in Fukuoka had risen to 35C with humidity above 75%, and in the preceding weeks daily highs lay between 32C and 37C, with it having been a month since the daily high fell below 30C. No formal cause of death has been publicly released, but the link suggested by the club between training in heat and Vunilagi's death has caused alarm given the increase in global temperatures and the rising frequency of extremely hot days.

There have been several heat‑related medical incidents in sport during 2026: tennis players Jakub Mensik and Ekaterina Alexandrova collapsed during matches played at more than 30C, eight runners were taken to hospital during a marathon in South Korea in April when temperatures reached 29C, Tour de France winner Tadej Pogacar described this year's heat as "dangerous" during the event, and Matthew Brennan asked "what are we doing?" after the temperature topped 40C at the Vuelta a Espana, in which he won five stages. This summer's World Cup included hydration breaks at every match, which Fifa insisted were introduced to aid player welfare.

Many sports use the Wet Bulb Globe Temperature (WBGT) to monitor potentially dangerous heat: the measure assesses air temperature, humidity, wind speed, sun angle and solar radiation to estimate heat stress levels. Some experts argue current protections are insufficient and that athletes need greater safeguards to prevent further 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," says Dr Madeleine Orr, assistant professor of sport ecology at the University of Toronto.

Specific on‑court cases underline the risk: Jakub Mensik was helped by rival Mariano Navone after collapsing at the end of a five‑set match which lasted four hours and 41 minutes and was played in more than 32C heat. That incident followed other collapses in conditions above 30C and has fed calls for clearer, more uniform protocols across competitions and venues.

There are growing calls for blanket rules so organisations adopt a consistent threshold for action. "Different leagues have different policies - there needs to be more of a standardised approach so that everyone just knows what to do," Orr says. "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 - it's easier for people to get behind if it's universal that once we get to a certain threshold, we know what happens." Christian Day, general secretary of the Rugby Players' Association, adds: "I've got no doubt that a lot of coaches think that heat regulation is a hindrance. And it's a tough one for the player, isn't it? Because you don't want to be the player who puts their hand up and says they're not feeling well, or that it's too hot to train on a certain day. Players need protecting from themselves sometimes. It's important for team staff to have a regulatory number that they know if it hits it, there's no discussion, you just stop playing. It's also about educating players as to what signs to look for to identify one of their team‑mates who is struggling in training." World Rugby updated its heat and air‑quality guidelines in 2025, introducing a heat stress index — a measure from 0 to 250 used to determine danger to players — with provisions ranging from additional water breaks and extended half‑time periods at lower levels to possible suspension or postponement at the higher end of the scale.

Day argues that central regulation is needed because players spend far more time training than playing matches: "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," he says. "Maybe there are cases where perhaps training needs to be limited in time, or doesn't take place at all that day outdoors. It's not a matter of trying to call people out or produce problems. It's trying to ensure the safest possible training environment." By early August the Japan Meteorological Agency had recorded 4,727 instances of 'extremely hot' temperatures across the country since the start of 2026.

Heatstroke is described in medical terms in the article as a sudden, dangerous condition that occurs when the body overheats and can no longer cool itself, with the potential to damage organs, cause the intestines to release toxins and be fatal within little more than an hour; symptoms include dizziness, nausea, headache, confusion and slurring. "Heatstroke is 100% preventable, so every single death is one too many," Orr says. "It's not the case that athletes can handle heat better because of their fitness. And the bigger the body the faster it heats up, so bigger bodies are more vulnerable as well. Moving that mass around takes a lot of energy. So while yes, professional athletes are extraordinarily fit, that doesn't save them when the issue of concern is cooling off the body." On the wider impact, Day adds: "Whatever the elite level does, we'll see it trickle down into grassroots. 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."

National and sport governing bodies have already issued guidance and warnings this summer: on 5 June 2026 the Japan Rugby Football Union warned clubs that heatstroke was an increasing concern during the summer and told teams safety should be the overriding priority when planning summer training camps, a step that mirrors calls from players' unions and medical experts for clearer, enforceable standards for training and matches in extreme heat.