Since 1900, the mean annual temperature in Tokyo has increased by 2.86°C, which is more than three times the global average.
Tales of fainting archers and volleyballers burning their feet on baking sands have seen a flurry of claims that the Tokyo Olympics are the hottest to date. This has come as no shock. In 2019, already, specialists predicted Japanese summer conditions would break records and challenge athletes.
Since 1900, the mean annual temperature in Tokyo has increased by 2.86C, which is more than three times the global average. Research has found this is due to changes in land use with urbanisation creating the second largest metropolitan area in the world and an urban heat island. This traps heat during the day and causes high night-time temperatures.
Add high humidity (above 70 per cent) and – for triathletes and marathon swimmers – high open-water temperatures, and the Tokyo Olympics represent the greatest thermal challenge of recent Olympiads (see the graph below).
Our recent research has looked specifically at how athletes’ ability to perform in Tokyo will be impacted. We have spent the last two years helping the English Institute of Sport work with athletes to ensure they are properly acclimatised to the conditions under which they now compete.
When exercising, between 75 per cent and 80 per cent of the energy consumed by the body is released as heat. Normally, we can get rid of this heat by losing it to a cool environment – the ideal air temperature for endurance sports is about 11C.
When air temperature gets close to skin temperature (between 30C and 35C) the only route for heat loss is the evaporation of sweat. This becomes more difficult as the amount of water vapour in the air increases. In a hot, humid environment the body struggles to lose the heat generated by exercising.
Overheating can compromise the function of the muscles, heart and circulation, and these effects are compounded by the dehydration caused by sweating. As a result, it will be a surprise if endurance events in the heat and humidity of Tokyo produce any world records. Even just standing in the heat for long periods, as Russian archer Svetlana Gomboeva’s recent collapse demonstrates, can negatively affect blood pressure control.
Heat can also affect cognitive function, especially in complex tasks, the ability to maintain attention and short-term memory. It can adversely impact your mood and sense of comfort, as well as the sensation of fatigue.
Feeling hot, or the body’s responses associated with heat exposure, such as sweating, can be distracting. It affects concentration and thereby performance in both sports and any officiating duties, where focus and attention are required.
More seriously, the combination of high air temperature, high humidity and high solar and radiant heat load (the radiant heat directly from the sun and heated surrounding surfaces) creates excessive thermal stress. As a result, your core temperature, which is normally at 37C, can increase uncontrollably. As research has highlighted, such conditions should lead to events being cancelled according to international guidelines. Allowing them to go ahead leaves athletes facing a high risk of heat illnesses. These range from cramps and fainting to exhaustion and heat stroke, a serious medical condition with long-term, multi-organ consequences (see graph below).
Threat to health
The first of several possible mitigation strategies is to schedule events in cooler regions or at cooler times of the day. While the 50km men’s and women’s walking races, marathons and soccer competitions have been relocated to Sapporo, where temperatures are about 6C lower, the heat island effect means there is no cool part of the day in Tokyo.
Cooling breaks, like the ten-minute pauses now common practice in tennis tournaments, can be introduced into events. These appear ineffective – too passive, too short – in reversing the problems tennis players are experiencing in Tokyo. The Spanish player Paula Badosa has retired from play due to heatstroke, while the Russian player Daniil Medvedev recently asked an umpire who would be responsible if he died.
Other strategies include drinking ice slushies and (hand cooling, as well innovative wearables (cooling gloves, ice vests, UV parasols).
Finally, and most importantly, is acclimatisation (in the field) or acclimation (in the lab). In order to adjust physiologically and psychologically, athletes must repeatedly practice and train under hot conditions. Specialists recommend that levels of acclimatisation – or, conversely, difficulty dealing with heat – be taken into account during selection processes.
The goal of our work with Team GB via the English Institute of Sport has been to help participants avoid heat illness and maximise performance. Hockey squads, rugby players, triathletes and others spent weeks training in greenhouse tents – individual acclimation labs set up to be used in a COVID-safe way. Others have used post-training hot baths to stimulate the acclimation process.
With climate change and associated extreme weather events, the likelihood of an Olympics taking place in hot, humid environments increases. In addition to health threats, the overall experience will be diminished by uncomfortable conditions for spectators and impaired performance by athletes and officials.
Just as locations for the winter Olympics are being limited by climate change, the International Olympics Committee will have to give serious consideration to where and when they hold future Summer Olympiads if they want records and top quality performances. Sports fans should demand cooler environments so they can witness elite performances unimpaired by heat.
In 1964, the first Tokyo Olympics were held in October to avoid the summer heat. As the New York Times recently put it, it was hot then and, thanks to the climate crisis, it is hotter now. Perhaps the time has come for the Summer Olympics to become the autumn (fall) Olympics?
Mike Tipton is a Professor of Human and Applied Physiology, and Dr Jo Corbett is Associate Head for Research within the School of Sport, Health and Exercise Science in the Faculty of Science and Health.