Calling out the impact of extreme heat on athletic performance
After much anticipation, we witnessed four weeks of intense competition and athletic prowess during the 2024 Paris Olympics. As athletes fight for gold and glory, they push their bodies to the absolute limit. However, environmental factors can get in the way of their dreams.
At the last summer Olympic Games in Tokyo, athletes endured temperatures exceeding 34°C and humidity levels of 70%. These conditions were tortuous for athletes and caused severe health risks. Since then, many have raised the alarm about climate change’s impacts on sports.
Ahead of this year’s games in Paris, BASIS and Frontrunners have collaborated to produce “Rings of Fire,” a report combining climate science and athlete testimonies on how climate change and extreme heat threaten the ability to compete safely.
If there are records athletes want to see broken, 2023 being the hottest year on record is not one of them. Climate change threatens athletic performance, from sleep disruptions and event timing changes to heat stress and injuries.
With rising average global temperatures, athletes should prepare themselves for how extreme heat will impact their training and events. Adaptations will be required not only to drive performance but also to protect themselves from heat-related health risks.
Raising awareness on how heat impacts the health of athletes
When we think about how heat impacts the ability of athletes to perform, there are three main risks:
- Heat stroke: In these instances, the body temperature rises above 40.5°C and causes the thermoregulatory system to fail.
- Heat exhaustion: When impacted by this heat illness, athletes are unable to continue exercising, as when we see competitors collapsing on race courses.
- Heat cramps: Athletes are more prone to cramps caused by dehydration, low energy stores, and changes in electrolyte concentrations.
The last thing we want to see is athletes risking their health and putting their lives in danger. In Rings of Fire, athletes such as Pragnya Mohan spoke out against the health risks athletes face when training and competing in intense heat.
“Triathlon is a very intensive sport and heat enhances the amount of energy required. This leads to severe dehydration resulting in cramps, and in some cases can also be fatal. For this reason, athletes need to train in such conditions because it can lead to adverse effects if your body is not used to it.” Pragnya Mohan, India’s highest-ever ranked triathlete speaks out on heat risks.
Pragnya Mohan, India’s highest-ever ranked triathlete.
Exploring how heat impacts performance in endurance sports
Heat can have a detrimental impact on athletic performance as it can increase the body’s temperature and perceived exertion, challenge the cardiovascular system and alter the optimal balance of fluids (1) in the body. Two interrelated factors are at play:
Thermoregulation
When exposed to high temperatures, the body will react by increasing blood flow to the skin and secreting sweat to regulate its temperature. However, exercising in warm environments makes it harder for the body to evacuate the heat and regulate its temperature.
In these instances, the body will focus on cooling rather than delivering oxygen to the muscles, which is where we see decreases in performance, especially in endurance sports, where athletes are exposed to heat for an extended period of time and need to sustain high levels of effort.
Dehydration
When sweating, athletes lose fluids. Inadequate replacement of these fluids in extreme heat could lead to dehydration, which could raise body temperatures and exacerbate thermoregulation issues.
Additionally, performing in warm environments will increase the body’s need to cool and sweat, leading to water and electrolyte loss. In these instances, the loss of fluids can negatively impact aerobic performance as blood flow to the muscles (2) is reduced.
Results in heat
Despite their rigorous training, even elite athletes can see their performances negatively impacted by heat, as it causes:
- Exhaustion: In an analysis of the impact of heat stress on aerobic performance, researchers found that the time to exhaustion could be up to 42 minutes shorter (3) when athletes performed at 31°C compared to 11°C.
- Lower power: In a 30-minute time trial, elite cyclists’ power output was 6.5% lower (4) when they performed under 32°C compared to 23°C, with higher skin temperatures and heart rates experienced in warmer temperatures.
- Performance losses: When studying elite marathon athletes, it was found that their running performance decreased by 2 to 3 minutes (5) when the temperatures increased from 10°C to 25°C, which could significantly impact race positioning.
Heat can negatively impact athletic performance in endurance sports. However, heat impacts athletes differently, and preparation can mitigate its effects on performance and prevent health risks.
How athletes can prepare themselves to perform in the heat
When preparing to race in warm temperatures, athletes and coaches can proactively adapt training schedules, intensity and location, as well as race day strategies.
Heat acclimation
Athletes can create physiological adaptations, such as thermal comfort or heart rate habituation, by artificially exposing themselves to heat during exercise. They can train in heated chambers and take hot baths or use saunas (6) after a session.
Heat acclimatisation
To adapt to warmer environments, it is recommended that athletes spend 10-14 days (7) in the event location before race day. They should start with short and easy training sessions in the heat and build up exposure to warmer temperatures before the actual event.
Heart rate training
When athletes start incorporating heat training into their schedules, they should be mindful of the changes in conditions and should not expect to race at the same speed or for the same distances. Training in their heart rate ranges and respecting them can prevent risks of heat illnesses.
Adapting nutrition
Nutrition strategies for races and training in the heat should account for the fact that athletes may lose more fluids and electrolytes than under normal conditions. Appropriate hydration before, during and after the race can reduce risks of dehydration and ensure adequate thermoregulation.
Overall, when preparing to perform in warm temperatures, athletes who expose themselves in training to similar expected conditions on race days can enhance psychological and physiological adaptations that will benefit performance.
For the 2019 World Athletics Championships in Doha, 63% of athletes (8) underwent heat acclimation or acclimatisation before the championship. Those who did performed better and were less exposed to heat risks than those who had not followed such practices in training.
In a future increasingly impacted by extreme weather events, athletes should be mindful of the location of their races and expected temperatures, taking appropriate measures to minimise health risks and ensure they can sustain high levels of performance in warmer environments.
References:
- Cheuvront et al. (2010). Mechanisms of aerobic performance impairment with heat stress and dehydration. (1)
- González-Alonso, Calbet & Nielsen. (1999). Metabolic and thermodynamic responses to dehydration-induced reductions in muscle blood flow in exercising humans. (2)
- Galloway & Maughan. (1997). Effects of ambient temperature on the capacity to perform prolonged cycle exercise in man. (3)
- Tatterson et al. (2000). Effects of heat stress on physiological responses and exercise performance in elite cyclists. (4)
- Ely et al. (2007). Impact of weather on marathon-running performance. (5)
- Heathcote et al. (2018). Passive Heating: Reviewing Practical Heat Acclimation Strategies for Endurance Athletes. (6)
- Tyler et al. (2024). The effects of heat adaptation on physiology, perception, and exercise performance in the heat: An updated meta-analysis. (7)
- Racinais et al. (2022). Association between thermal responses, medical events, performance, heat acclimation and health status in male and female elite athletes during the 2019 Doha World Athletics Championships. (8)