Olympics 2024: How athletes are preparing for the heat of Paris

With only days to go until the opening of the Paris 2024 Olympic Games, we feature our next expert insight from an Oxford Brookes University academic.

The 2021 Summer Olympics in Tokyo were the hottest ever. Temperatures reached 34C, and a humidity of 70% means that it would have felt like 47C. With the 2024 Paris Olympics starting soon, average temperatures in Paris have risen by about 3.1C since the city last hosted the Games in 1924.

Mark Hines, Senior Lecturer in Exercise Physiology at Oxford Brookes University, analyses how top level athletes will prepare for the Parisian heat, whilst also maintaining their world class skills and abilities. 

Mark has expertise in the effects of exercise in extreme temperatures. He leads a fieldwork module for students, in which they are put into demanding environments to then measure the effects on the human body. 

How will Olympic athletes prepare for the potential extreme heat during the Games? 
“There will be a mix of approaches, influenced largely by where the athletes are based, and what facilities they have available. If athletes can live and train in conditions that are hotter and more humid than what they will encounter in Paris, they will acclimatise and be well-prepared. Strategies can include moving to hotter countries for the weeks before the event, or using environment chambers that simulate those conditions. Environment chambers can vary from high-tech sealed rooms that control temperature and humidity, to more improvised facilities that are really just big tents with heaters installed. Simpler and more accessible strategies include making use of saunas and steam rooms, and wearing more clothing during training.”

How can extreme levels of heat or humidity affect the performance of an elite athlete?
“There are a few mechanisms that can impact performance. When an athlete sweats, they are losing water and salts to the environment in an effort to lose heat from the body. The hotter it is, the more they will sweat. The more humid it is, the less effective sweating is at cooling, because the sweat cannot evaporate into an already wet environment. This means that heat and humidity increase the risk of dehydration, and it only takes an athlete to become dehydrated by 1 to 2% for it to have an impact on performance and coordination. 

“Another problem with dehydration is that water loss ultimately reduces how much water is in an athlete’s blood. This means there is less blood in total, so the heart must beat faster to ensure enough is reaching the muscles and lungs. This is compounded by more blood being directed to the skin for cooling, rather than mostly circulating between the heart and muscles. Higher heart rates cause fatigue to occur earlier, which is one of the reasons the fastest marathon times typically happen in milder conditions. For athletes, it is why it is really important to monitor hydration before and during competition. This can be achieved by regularly measuring body weight and fluid intakes, although it is also possible to analyse urine, and/or use patches on the skin to measure sweat composition.”

Are some athletes more vulnerable to extreme heat due to the Olympic discipline they compete in? 
“Events requiring longer periods of continuous exercise in the heat, such as distance running and triathlons, will undoubtedly cause athletes to struggle more than those involved in fairly short strength and power activities. But, considering everyone can be susceptible to the effects of heat on coordination, it has the potential to impact all athletes in some way.

“Athletes who already live in colder countries will be more susceptible to the heat than those who are already well acclimatised. In long-distance endurance events, such as the 10k run, triathlon and marathon, as well as sports such as tennis, athletes who are not used to hours competing in the heat will be at a disadvantage. Athletes from hotter countries will have developed their bodies and minds to tolerate increased temperatures, so other athletes have to work harder in training to compensate for this.  

“For example, elite marathon runners have been found to tolerate higher core temperatures than non-elite runners, and it is likely that runners from hotter countries have a better heat tolerance than others, so can withstand higher temperatures in competition before feeling its effects. Of course, there are various other reasons why some athletes perform better than others, such as body shape, genetics, training programmes and the clothing or equipment they use, so we cannot really single out one factor. Nevertheless, tolerance of heat through living and training in hot environments will be advantageous.”

With the effects of climate change likely to lead to even warmer temperatures, are future Olympic Games hosted in the summer months at risk? 
“I do not think the heat itself is going to be a real barrier for athletes training to compete in the Olympic Games.  Athletes are already pushing themselves as hard as they can during their events, and the trends towards higher temperatures will not be enough to jeopardise the Games alone. 

“However, both the winter and summer Olympics could be impacted by extreme weather events, and I expect that organisers will have to consider timing the Games for when risks are lower. Due to the fact that extreme heat could have potentially disastrous effects on athletes during some events - such as the marathon - the importance of appropriate acclimatisation to increased heat, as well as better athlete monitoring by sports scientists becomes more important.”

Are there any new technological tools, gear or sportswear that athletes will use to manage their body temperature during competition, such as clothing or equipment designed to keep them as cool as possible?
“I expect there will be a combination of the tried and tested approaches to managing heat, and the use of newer technologies too. For example, managing hydration is key, because dehydration negatively impacts performance. There can be a short-term benefit to consuming more water than is needed - a strategy called ‘hyperhydration’ - which helps keep the body cooler for a few minutes, until the kidneys are able to remove and eliminate the excess. Managing hydration during longer periods requires intake of electrolytes - to help replace the salts being lost through sweat. Failure to do this is a mechanism that can cause serious harm to the body.

“Using cold baths or showers before exercise can help to keep the body cool, but can also limit muscle function. Cooling vests are a newer and better option that athletes can wear pre and post competing, because the muscles in the arms and legs can remain warm and ready to perform, whilst the core temperature is prevented from getting too high.”