Scientific research Thermo Tokyo

Thermo Tokyo Beat the Heat

In the summer of 2021, the Tokyo Olympic and Paralympic Games will be held in Tokyo. At that time, the ambient temperature will be above 30°C and the humidity can reach 75%. These circumstances will be the most challenging ever observed during the Olympic and Paralympic Games.

In the Thermo Tokyo project, an interdisciplinary consortium consisting of representatives of the Radboudumc, the HAN University of Applied Sciences, VU University Amsterdam, Delft University of Technology, and NOC*NSF, work together to beat the heat and to be a step ahead of the competition during the Tokyo Olympics. To achieve this goal, several studies have been carried out.

Between November 2018 and February 2020, 130 Dutch elite athletes performed personalized exercise tests in the climate chamber at Papendal. These tests were used to determine how heat impacts their physiological responses and performance capacities during exercise in the heat. In two other studies, we investigated how acclimatization can be performed best, which cooling strategies are most effective, and how cooling strategies can be optimized for specific sports.

Based on these scientific insights, countermeasures such as heat acclimatiztion and cooling interventions have been personalized, and by this, the Thermo Tokyo consortium contributes to safe and maximum exercise performance by TeamNL athletes during the Tokyo 2021 Olympic and Paralympic Games.

The rationale and design of the Thermo Tokyo study have been published in the scientific journal Temperature.  

Header photo by Guus Dubbelman.

The climate

The challenging climate during Tokyo’s summer was the reason to initiate this project. But what makes this climate so harsh for participating athletes?

During exercise, 80% of the energy is converted into heat. This causes the body temperature to rise. The warmer and more humid the environment, the more difficult it is to dissipate heat. The most effective way to dissipate heat is via evaporation of sweat. However, when the humidity is high, sweat evaporates less easily. As a result, the heat loss to the environment is limited and the exercise-induced increases in body temperature are larger than normal.

On an average summer day in Tokyo, the ambient temperature is around 30°C and the humidity can reach 75%. The combination of high ambient temperatures and high humidity during the Tokyo Olympic and Paralympic Games will result in very challenging circumstances.

Heat profile

During exercise and sports, the heat production in the body increases causing the body temperature to rise. Progressive increases in body temperature may cause substantial reductions in exercise performance and place athletes at a higher risk of developing heat-related illnesses.

Between November 2018 and February 2020, personalized heat profiles were obtained in 130 Dutch elite athletes. These profiles were based on two personalized exercise tests in the climate chamber at Papendal. Each athlete performed one exercise test in a cooler climate (15°C and normal humidity) and one exercise test in a Tokyo climate (32°C and high humidity). During both tests, extensive physiological measurements were performed such as monitoring of heart rate, body temperature, skin temperature, and sweat loss. These measurements allowed us to assess the effect of the Tokyo climate on exercise performance capacity and individual physiological responses.

The climate chamber measurements demonstrated that the Tokyo climate has a major impact on the exercise capacity of elite athletes. The average loss of performance was over 25% and the average maximum body temperature was 38.9°C. Surprisingly, the way athletes react to exercising in the heat largely varied. For example, the maximum body temperature varied between 37.6 and 40.4°C, while the degree of performance loss varied between 0 and 48%. These results emphasize that it is impossible to offer a ‘one-size-fits-all’ heat mitigation strategy to elite athletes and underline the importance to determine the individual’s needs for specific countermeasures.

Therefore, in collaboration with NOC*NSF and the medical staff of various sports associations, we worked hard to determined the individual’s need for heat acclimation, cooling interventions, and a hydration plan. Based on these insights personalized individual plans were developed. By this, the Thermo Tokyo consortium contributes to safe and maximum exercise performance by TeamNL athletes during the Tokyo 2021 Olympic and Paralympic Games.

Picture by Guus Dubbelman.

Acclimatization

The human body is perfectly capable of adapting to a hot and humid climate. However, it takes 10 to 14 days for the body to fully adapt. When fully acclimatized, the resting body temperature is lower, blood volume is increased, the athlete starts sweating earlier, and the resting heart rate is lower. With these physiological adaptations, an athlete may improve his performance in the heat by 30%.

In the Thermo Tokyo project, we investigated how athletes can adapt to the heat (acclimatization or acclimation (when performed in laboratory)) in the best way. We did this by determining the speed and degree of physiological adaptations and by exploring new re-acclimatization strategies. Re-acclimatization strategies have good potential as it is not possible for every athlete to travel to Tokyo to fully adapt.  

We found that the speed and degree of adaptations differ between individuals. It was remarkable that individuals with higher weight sweat more, while athletes with a lower weight show a greater drop in heart rate. After a 10-day acclimatization period, the physiological adaptations remain for several weeks, even when the body is no longer exposed to the heat. However, the sweating capacity seems to decrease faster. But, with a 5-day re-acclimatization, this maximum sweating capacity is easily regained. The effect of a 10-day acclimatization period on performance is great, but the effect fades away when the body is no longer exposed to the heat. In addition, the positive effect on performance cannot be regained by conducting a short 5-day re-acclimatization period only.

These results show that it is very important to adapt to the hot and humid Tokyo climate in preparation for the Tokyo 2021 Olympic and Paralympic Games. Heat exposure helps induce physiological adaptations which contribute to better temperature regulation and help to alleviate the heat-induced reductions in exercise performance. Since the time course of adaptations is different across individuals, it is important to plan and monitor the speed and degree of acclimatization at an individual level.

Based on these scientific insights, we have worked hard in collaboration with NOC*NSF and the medical staff of various sports associations to develop individual heat acclimatization programs. By this, the Thermo Tokyo consortium contributes to safe and maximum exercise performance by TeamNL athletes during the Tokyo 2021 Olympic and Paralympic Games. 

Optimal Cooling Strategies

Cooling strategies can improve sports performance during exercise in the heat by reducing the increase in body temperature. There are several cooling strategies used in sports to improve performance: cooling before exercise (pre-cooling) and cooling during exercise (per-cooling). Within each cooling strategy, there are various cooling methods available, such as wearing a cooling vest, drinking cold water or ice slush, using ice packs, and the application of menthol.

Cooling strategies can improve sports performance during exercise in the heat by reducing the increase in body temperature. There are several cooling strategies used in sports to improve performance: cooling before exercise (pre-cooling) and cooling during exercise (per-cooling). Within each cooling strategy, there are various cooling methods available, such as wearing a cooling vest, drinking cold water or ice slush, using ice packs, and the application of menthol.

With the Thermo Tokyo project, we have investigated the most effective cooling strategy and cooling methods to improve sports performance. Our data demonstrated that the use of ice baths is the most effective pre-cooling strategy and that cooling vests are the most effective per-cooling strategy. The results of this study have been published in the British Journal of Sports Medicine.

In addition, several new innovative cooling methods have been developed in collaboration with Inuteq. For example, innovative cooling vests have been developed for sailors (to be worn underneath the life jacket), hockey keepers (body protector and helmet), and equestrian sports (horse leg and rider's helmet). The use of these cooling methods during the Tokyo Olympic and Paralympic Games will help TeamNL athletes to be one step ahead of international competition.

Headerpicture by Irmo Keizer.