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The Outer Line: Climate change and endurance sports

Environmental factors are already significantly impacting elite sport, and will continue to influence pro cycling’s efforts to expand and bring the sport before a wider and more global audience.

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Sporting events are increasingly experiencing the consequences of climate change and the threat of extreme weather events. Although the COVID-19 pandemic is not a result or necessarily a reflection of climate change, it is neatly serving to illustrate both society’s impact on and reaction to climate change. With a higher frequency of event disruptions for pro cycling – which is dependent on its “outdoor arena” – what impacts can cyclists expect in the future, how can we physiologically adjust to these changes, and how can the sport navigate a successful future?

Stage 19 of last year’s Tour de France was famously neutralized to protect rider safety after a severe ice and hail storm – in late July – that caused mudslides and icy conditions on the descent of the Col de l’Iseran. Only a few months ago (though it seems like years ago) during the 2020 Santos Tour Down Under, the pro peloton rode through the burning embers of massive wildfires, at least partially the result of broader climate change. Stage 5 of the 2015 Tour of Oman ended amidst a sandstorm, after a mass argument ensued between riders and organizers over “security concerns” regarding extreme heat. (Rider Arnaud Démare claimed that his SRM showed a reading of 122°F). Similarly, Stage 2 of the 2014 Tour of Beijing was shortened by 36 km, due to smog and extremely poor air quality. During what turned out to be the last edition of that race, a number of top-level riders including Alberto Contador, pulled out because of potential health concerns related to excessive pollution.

There are numerous other examples that suggest that environmental pollution and increasing average temperatures are impacting sports more generally. The gradual warming of the earth (the average global temperature has risen by about 2° F over the last century) along with increasingly frequent and more severe heatwaves have been linked to a number of health problems, including cardiorespiratory difficulties amongst endurance athletes. As these effects emerge and become clearer, we have to ask: what do these anecdotal examples from pro cycling tell the rest of us – as amateur endurance athletes or enthusiast runners and cyclists – about the potential risks we face?

The 2020 Santos Tour Down Under was staged amid wildfires. Photo: Tim de Waele/Getty Images

Robust data regarding air quality, air temperature, and humidity are well known for their effects on our general health and athletic performance. Indeed, Director General of the World Health Organization (WHO), Dr. Tedros Adhanom Ghebreyesus, has identified air pollution as “the new tobacco.”  According to WHO statistics, 9 out of 10 people worldwide breathe air containing high levels of pollutants, with poor air quality contributing to nearly 7 million deaths annually. Scientists at The University of Cologne showed that the performance of professional soccer players in Germany’s premier Bundesliga was negatively affected, and their style of play significantly adjusted, when exposed to high levels of pollution. Several French research groups have specifically identified air pollution and elevated temperature to be the two most important environmental features contributing to Life-Threatening Events (LTE) – including heatstroke, heart attacks, and sudden cardiac death – during sporting competitions.

Although less frequently mentioned, relative humidity also impacts athletic performance. The percentage of both LTEs and competitor withdrawals from endurance races increase as both temperature and humidity rise. Consequently, experts have concluded that many LTEs could have been prevented if the athletes anticipated adverse environmental conditions – heat, humidity, and poor air quality – appropriately prepared for them, and promptly reported any cardiorespiratory symptoms to course marshals, rather than simply “soldiering-on” in an attempt to finish the race.

In the future, climate change and extreme environmental conditions will likely begin to rule out possible event venues that are more prone to excessive heat or poor air quality. This will undoubtedly have profound effects on athlete safety.  The selection of Qatar as the home for the 2022 World Cup has thrust this issue squarely into the public eye.

Tejay Van Garderen
American Tejay van Garderen skipped the Rio Olympics due to the Zika virus. Photo: Tim De Waele |

We are already seeing examples where different types of venue selection concerns have narrowed the pre-race field of elite competitors – profoundly influencing the podium, and undermining the overall quality of an event. Despite the fact that Beijing banned traffic for a few weeks prior to the games to clean up the air, Haile Gebrselassie shocked the sports world by refusing to run the marathon at the 2008 Beijing Olympic Games. He feared for his health as an asthmatic and decided not to defend his world record marathon time because it just wasn’t worth the risk: “The pollution in China is a threat to my health and it would be difficult for me to run 42km in my current condition.” Closer to home, Tejay van Garderen opted out of the Rio Olympics, fearful of contracting the Zika virus, and what the potential impact might have been had he transmitted it to his pregnant wife.

Cyclists at any level, from weekend enthusiasts to pro racers, should be mindful of the potential dangers of competing in adverse conditions of excessive heat, humidity or poor air quality. All of these can lead to short and long term health risks – not simply a decrease in athletic performance. Riders with prior heart conditions, respiratory issues, or other health problems such as diabetes and high cholesterol, seem to be more susceptible to environmental influences during competition or training. General guidelines recommend caution when exercising in temperatures above 80° F or in relative humidity greater than 75 percent. Some athletes may choose to exercise indoors in these situations.

Fitness level, hydration status, and prior acclimatization to adverse environmental conditions all help to mitigate heat-related injury, but as we have seen, sometimes even professionals need to pull the plug on an event.  Riding earlier in the morning, which is typically a cooler time of the day, is a helpful strategy to avoid heat exhaustion. Early morning exercise may also be preferable since air pollution levels increase to their highest levels mid-day, and toward the afternoon rush hours — particularly in urban areas.

Strategies to minimize exposure to air pollution are equally important. Local radio and television stations often report air quality statistics; if an air quality alert is issued in your area, you may want to avoid exercising outside, particularly if you are a member of an at-risk group. If possible, avoid high pollution areas such as cities and heavily traveled roads while riding.  Depending on specific goals and available resources, some elite-level racers actually try to achieve marginal gains by training in areas with better air quality than where they live or are expecting to compete. Consider varying your exercise routine with an indoor cross-training workout if air quality is truly poor.

As we have said before, you are your own best health advocate. Even some top professional athletes refuse to compete, if they believe their health may be compromised. From the broader perspective, and regardless of any personal commitment or competitive spirit,  it seems silly and pointless to race your bike, run a race, or complete a triathlon for a piece of tin around your neck and a t-shirt, if you are risking your health or even your life. Better to lose your registration fee. And never violate this cardinal rule: If you start to feel poorly, just stop. Data clearly shows that in the majority of competition-related LTEs, athletes chose to ignore what their body was telling them, in an attempt to finish the event. Nearly one half of LTEs may be preventable simply by acknowledging symptoms.

In short, environmental factors are already significantly impacting elite sport, and will continue to influence pro cycling’s efforts to expand and bring the sport before a wider and more global audience. But at a fundamental level, the changes could affect all of us and how we participate in cycling. However, one of the possible “silver linings” of the COVID-19 era is that it has allowed us to at least briefly hit the global environmental “reset button,” and let everyone – not just endurance athletes – pause for a moment, and examine the ways our environment impacts not only short-term athletic performance but also long-term health and fitness. We have seen some remarkable and encouraging short-term changes, with a substantial portion of the world’s population on lockdown over the past few months.

2008 Olympics in Beijing, China.
Many were concerned about air quality at the 2008 Olympics in Beijing, China. Photo: Tim de Waele/Corbis via Getty Images

In New York City alone, desperately struggling to contain coronavirus, traffic volume was down some 35 percent compared with a year ago, and emissions of carbon monoxide, usually generated from avenues clogged with cars and trucks, fell an astounding 50 percent. NASA satellite imagery undeniably shows that airborne nitrogen dioxide levels have correspondingly “plummeted” – especially over densely industrialized regions like China – probably a direct consequence of government-mandated factory shutdowns that began in January. A picture is worth a thousand words and in India, for the first time in 30 years, the peak of Mount Everest is visible from 125 miles away.

There is longer-term hope. The current and widely-documented increased interest in cycling has been born out of “quarantine fatigue.” Cycling can allow us a means of getting outdoors, exercising, and physical distancing without depriving us of social interaction – it has become one mechanism to appropriately deal with the psychological ravages of COVID-19. As has been the case in Europe for years, many more Americans are looking at the possibility of commuting to work on their bikes. In addition, as more people have been working at home, and with more companies realizing that it is feasible for many employees to work at home indefinitely, we may hopefully begin to rethink our daily work commute altogether. And as more of us become cyclists, perhaps society at large can become more accepting of cyclists, and we can make permanent improvements to cycling-related infrastructure. If some of these things started to gradually happen, over time it could lead to a reduction in one of the primary causes of air pollution.

While there is a complex interplay between human activity and environmental science, climate change has become more visible to cycling participants. These changes ultimately affect how we enjoy our sport whether it is a race cut short to the dismay of millions of fans, or a ride you have to cut short due to temperature extremes and your own health. Be self-aware of your limitations in adverse conditions, and stop riding when you feel you might be into your “red zone.” While the ongoing lockdown has provided at least a brief and transient glimpse of short-term positive environmental effects, extreme conditions that persist can have long-term impacts on your personal health.


Dr. Bill Apollo, an amateur bike racer, runner, and duathlete, is a Harrisburg, Pennsylvania-based cardiologist, and medical director of the UPMC Pinnacle Sports Cardiology Clinic.

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