Extreme Heat: When Outdoor Sports Become Risky

Extreme Heat: When Outdoor Sports Become Risky

The most recent decade was the warmest in the United States since record keeping began in 1895. And 2019 saw some of the hottest months on record globally.  Extreme heat is intensifying with climate change, and even small increases in averages can have big impacts on extreme temperatures. 

All regions of the country are projected to experience higher temperatures in the future, with the magnitude of temperature increase largely determined by the amount of emissions we produce now and in the near future. In July, the Union of Concerned Scientists published research that projected the effect that global warming will have on the number of days per year in which the heat index will rise above 90°, 100°, and 105°F through the end of the century. The UCS analysis found that in many U.S. cities, extreme heat conditions will rise from just a few days each year to weeks or months by 2050. By the end of the century, much of the summer could become dangerous for millions of Americans to work or be active outdoors. 

Extreme Heat and Sports: A Potentially Lethal Mix

Exercising outdoors when the heat index is high can add increased stress to your body. Body heat production rises during strenuous exercise, compared to when you are at rest. During intense exercise, maintaining a healthy body heat balance is highly dependent on the evaporation of sweat. On high humidity days, when sweat cannot evaporate from your skin, you are at risk of a variety of heat-related illnesses, from heat exhaustion to heat stroke.

School Sports

According to the Center for Disease Control, heat illness is a leading cause of death among high school athletes. Since 1995, 64 football players have died from heat stroke (47 high school, 13 college, two professional, and two organized youth), with nearly all of them (90%) occurring during practice. Although successful treatment strategies are being implemented, athletes are still succumbing to exertional heat illness (EHI), and heat stroke is a leading cause of sudden death during sports activities. As climate change threatens to increase high heat index days around the country, athletic trainers, coaches, and medical professionals will need to be educated and prepared to respond to, prevent, recognize, and treat EHI in athletes of all ages.

The University of Connecticut's Korey Stringer Institute (KSI) studies heat stress in sport and is named after the Minnesota Vikings offensive lineman who died from exertional heat stroke in 2001. Dr. Douglas Casa, the chief executive officer of KSI, is working with high school athletic associations in all 50 states to promote instituting state level policies for preventing heat illness, as there is no one national governing body. Casa’s research has found that states have very mixed records in terms of high school sports safety policies, including for practices or competitions on high heat and humidity days. Two years ago, KSI issued a report ranking all the states on meeting best practices for safety, and since then, about 30 states have instituted changes to upgrade safety policies. Many of the state-level high school association governing bodies are made up of former coaches or athletic trainers, and KSI’s mission is to bring professional medical expertise and evidence-based research to direct state policies.

One of KSI’s top recommendations is for schools to institute wet bulb globe temperature (WBGT) monitoring to more accurately measure local heat and humidity conditions. Long in use by the military, a WBGT device measures and incorporates ambient temperature, relative humidity, wind, and solar radiation from the sun. A shadeless, artificial-turf football field, surrounded by an 8-lane blacktop running track can have a microclimate of its own, says Casa. 

He acknowledges about a dozen states are using WBGT devices to monitor heat conditions for high school sports.

It’s More than Just High School Sports

Extreme heat is impacting sporting events around the world—at all levels, from youth to amateur to professional.Japan’s deadly summer heat waves have caused the 2020 Tokyo Olympic organizers to reschedule the Olympic marathon to begin at 6 a.m. to avoid the highest heat at mid-day and to put in place measures to keep spectators and participants safe from the heat and humidity next summer. Last September, for the first time, the heat rule was extended to male players at the U.S. Open, allowing male competitors to take 10-minute breaks between sets. But five players withdrew from competition due to the heat that day, which reached a heat index of 102°F.    

Cancellation of major events can also be costly for participants, the organizers, and the cities that host them. In July, the Haskell Invitational, the biggest horse race of the year for Monmouth Park Racetrack in New Jersey, was delayed for several hours due to extreme heat, and a number of other races that day were cancelled to protect the horses. The decision caused a financial hit, with the park taking in $8.6 million in betting instead of an expected intake of $20 million. 

Parents, Guardians, and Coaches: What You Can Do  

The National Athletic Trainers’ Association has developed a series of recommendations for the prevention, recognition, and treatment of exertional heat illness, and the Centers for Disease Control provides an online course for coaches. These recommendations cannot guarantee full protection, as individuals’ conditions and responses will vary, but they offer ways to mitigate risk of heat exertion illness. The NATA website provides a number of handouts and other guidance for parents and coaches

  • Prior to exercise, athletes should undergo medical screenings for previous heat illness incidents and other conditions. Any current sickness, such as a virus or fever, should disallow participation.
  • Identify individuals who may be at more risk for exertional heat illness and monitor them closely. Keep emergency equipment onsite, such as tubs for cold-water immersion.
  • Design workouts and physical activities to mitigate risks.
Heat acclimatization—progressively increasing the intensity and duration of physical activity—should be done gradually, over 7 to 14 days.  Rest breaks in the shade or in a cool area should be planned, include fluids, and allow athletes to remove equipment like helmets.
  • Fluids should be made available at all times, not just during designated breaks, and instruction should be given to athletes on eating and drinking appropriately to replace sodium loss in sweat.
  • Educate all personnel (coaches, trainers, medical staff, athletes) on preventing and recognizing exertional heat illness and stroke, and develop policies for organized sports and events taking place in hot, humid conditions.

Athletes: What You Can Do

The Korey Stringer Institute provides guidance for heat acclimatization, for athletes and others planning to train or participate in an event when high heat and humidity are forecast, with acclimating to the heat over 7 to 14 days a top recommendation. Their website also provides detailed advice, videos, and resources to prevent, recognize, and treat heat-related illnesses, including heat exhaustion, heat cramps, heat stroke, and heat syncope (fainting and dizziness). 

The Center for Disease Control also offers advice for athletic activities in extreme heat.  Among CDC’s tips:

  • “Limit outdoor activity, especially during the middle of the day when the sun is hottest.
  • “Pace activity. Start activities slow and pick up the pace gradually.
  • “Drink more water than usual, and don’t wait until you’re thirsty to drink more. 
  • “Monitor a teammate’s condition, and have someone do the same for you.
  • “Wear loose, lightweight, light-colored clothing.”


The daily maximum temperature and minimum relative humidity was assessed from 1979 to 2018 at the 239 contiguous U.S. stations typically analysed by Climate Central, using the gridMET modeled dataset and based on the findings of Dahl et al. 2019. Heat index temperatures were calculated using the National Weather Service’s heat index algorithms. The change in the number of 90°F+ and 105°F+ days are based on linear regression. Local graphics were not produced for Eureka and Monterey, California or Flagstaff, Arizona due to a lack of days in which the calculated daily heat index met or exceeded 90°F during the study period.

 This Article Originally Appeared On Climate Central

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