Simulations by Swedish engineers show that athletes competing in the Tokyo Olympics are at risk of heat shock, dehydration, and heat exhaustion due to high temperatures.
Running in conditions of 32 degrees Celsius and 90% humidity can cause the core body temperature to exceed the threshold of 39 degrees Celsius, posing a danger to athletes. In the 10,000-meter race, athletes could lose 710 ml of water, and the core temperature at the head could rise above 40 degrees Celsius. This can lead to dizziness, vomiting, seizures, and in severe cases, long-term damage to the nervous system and brain due to the effects of heat.
Simulation of the 10,000-meter race in hot and humid conditions. (Video: Hexagon).
Engineers at Hexagon, a Swedish technology company that specializes in simulation software for Airbus, Toyota, and Samsung, modeled the effects of hot and humid conditions on male athletes competing in the 10,000-meter race at the Olympic Stadium in Tokyo. Although this race is scheduled to take place after sunset on July 30, simulations indicate that athletes are likely to still face harsh conditions.
The engineering team created simulations based on two scenarios. The first scenario assumes an average temperature for this time of year at 27 degrees Celsius with 70% humidity. The second scenario features higher temperatures (32 degrees Celsius) and 90% humidity. In the hotter scenario, core temperatures can rise to 39 degrees Celsius, skin temperature to 37 degrees Celsius, and head temperature to 40 degrees Celsius. Consequently, athletes are at risk of cramps, exhaustion, and heat shock due to prolonged exposure to high temperatures and humidity. Calm weather conditions can also lead to fatigue and seizures.
Even under normal July weather conditions in Tokyo, runners may experience core temperatures exceeding 39 degrees Celsius. Temperatures above 38 degrees Celsius indicate fever, and research shows that humans need to maintain core temperatures between 35 – 39 degrees Celsius for biochemical reactions to occur normally. The thighs and pelvis are areas of the body particularly vulnerable to heat stress if air temperatures exceed average levels.
Humidity is also a crucial factor affecting athletes’ health and performance. For a race lasting 30 minutes, if humidity rises to 90%, athletes will lose an average of nearly 810 ml of water through sweating, compared to 630 ml under normal humidity conditions of 70% in Tokyo. While sweating helps cool the body through evaporation on the skin, on humid days when the air is saturated with moisture, this cooling effect is significantly less effective. Meanwhile, dehydration exacerbates the rise in overall body temperature, making the situation more severe.
The simulation focused on the 10,000-meter race, the longest running event in the stadium, but findings indicate that all athletes at the Olympics face harsh conditions, according to the Hexagon engineering team. “There has been much discussion about the decision to hold the Olympics in the summer in Tokyo. Athletes are accustomed to pushing themselves to the limit, and these simulations reveal how competition conditions impact performance and the risks when the body is pushed to extremes.”
Experts have also expressed concerns about the decision to hold this year’s Olympics during the hot summer in Tokyo. They warn against competing in such temperature and humidity conditions. The average temperature in Tokyo at the end of July and early August is the highest compared to any Olympic host city since 1984. The last time Tokyo hosted the Olympics in 1964, authorities had to reschedule to October due to similar concerns about heat.
The humid subtropical climate of Tokyo means hot and humid summers are unavoidable.
As the 2021 Olympic Games commence at the end of July, Tokyo is experiencing a heatwave with temperatures exceeding 34 degrees Celsius for several consecutive days. Although the Olympic Stadium is located in a developed area with elevated surface temperatures, there are green spaces nearby, such as Shinjuku Gyoen National Park, the Akasaka Palace grounds, and Yoyogi Park, providing shade and cooler temperatures.
The humid subtropical climate of Tokyo means that hot and humid summers are inevitable. However, there are many underlying factors that worsen weather conditions. Global warming has contributed to a temperature increase of 1.5 degrees Celsius in Tokyo since 1964 and 2.86 degrees Celsius since 1900, nearly three times the global average. Meteorological data also shows that the frequency of extreme heat events accompanied by high humidity has doubled since 1979.
The strong urban development has also led to significant temperature increases by creating “heat islands,” making the city hotter than surrounding suburban and rural areas. Urban development often results in higher ground temperatures due to construction materials like asphalt, steel, concrete, and brick that retain heat. In the case of Tokyo, this means that the ground is often several degrees warmer in the city, especially at night, compared to nearby green areas. Vehicles, factories, and air conditioning also contribute to heat islands by releasing heat into the atmosphere.
Researchers and analysts predict that this could be the hottest Olympic Games in decades based on meteorological data for July and August.
