As summer returns, so does the threat of heat illnesses in sports, primarily affecting those in regions with hot, humid days.1,2,3,4,5
In recent years, climate change has also caused heat illness to become a priority for other areas of this country where “heat waves have brought unseasonably hot and humid summer days.”1,2,5,6,7,8 “Although the proper recognition and successful treatment strategies are well documented, exertional heal illnesses continue to plague athletes. Exertional heat stroke (EHS), the most severe of the heat illnesses, remains one of the leading causes of sudden death during sport.”1
Heat illnesses fall on a continuum ranging from very mild, including heat rash, heat cramps, heat edema, and heat syncope, to the moderate heat illness of exertional heat exhaustion (EHE).1,4,5,6,8 If not recognized quickly and treated appropriately, EHS can lead to a myriad of complications, including but not limited to: multiple organ failure (including circulatory shock, hepatic failure, respiratory failure, renal failure, disseminated intravascular coagulopathy, rhabdomyolysis, encephalopathy, cognitive disability, and even death.1,2,3,4,7,9 Much of what is included in this paper regarding the diagnosis, treatment, and prevention of exertional heat illnesses (EHI) is applicable to those whose occupations include increased time and intensity of activity in hot and humid weather. Military personnel are included in this class of workers and often have the added risk of having to wear heavy clothing and carrying heavy gear.5,10,11,12 However, this article will focus on the recognition, diagnosis, and urgent management (prehospital management) of exertional heat illnesses in athletics.
Heat rash, one of the mildest forms of heat illness, is a pink or reddish rash most often found in babies and young children whose sweat ducts are still immature and can become clogged more easily than those in adolescents or adults.13,14 Heat rash responds well to taking off excess clothing, getting out of the hot humid area, and fanning the skin or placing a cool cloth gently over the affected area.
Heat edema or swelling in the extremities occurs secondary to the body trying to get rid of heat through peripheral vasodilation. Vasodilation is also believed to cause heat syncope due to reduced blood flow to the brain from peripheral dilation. Both heat edema and heat syncope respond well to moving the athlete to a cool shaded area, removing any excess clothing from the athlete, having the athlete drink cold water or a cold electrolyte replacement drink and having the athlete lie down with feet elevated. Fanning the athlete to help increase the sweat evaporation rate will speed cooling. If the athlete is in an area where there is access to an air-conditioned building, move the athlete to the air-conditioned building and, if available, use an electric fan to help cool the athlete. It is important to check vital signs (blood pressure, pulse, respiratory rate, and temperature) to make certain these are normal as other medical problems such as cardiac issues can masquerade as heat illness.
Exercise-associated muscle cramps (EAMCs) are painful contractions of large muscles, often caused by dehydration and excess electrolyte losses (sodium, potassium, and chloride) from sweating. There is still debate over the cause of EAMCs. One study did show that those who had had “frequent muscle cramps” did not have dorsal forearm skin sweat that was higher in salt concentration than those who did not have muscle cramping during exercise.15 Treatment for an athlete with EAMCs is to have the athlete sit or lie down in a cool environment and drink a cold electrolyte replacement drink like Gatorade, Powerade, Biolyte or Pedialyte and gently stretch and/or massage the cramping muscle. While pickle juice has garnered some popularity in reducing muscle cramps, it is felt that electrolyte replacement drinks or Pedialyte are better options, even better than some of the sports drinks, in that electrolyte replacement drinks generally have less sugar and additional electrolytes.15
Symptoms of EHE, a moderately severe heat illness, can include fatigue, low blood pressure, nausea or vomiting, headache, dizziness, weakness, orthostatic hypotension, fast pulse, cold clammy skin, a feeling of weakness, and an increase in core body temperature which is less than 40.5 0 C or 1050 F.1 Core body temperature must be measured with a rectal thermometer. Measuring temperature orally, under the axilla or through the skin, will not provide an accurate reading of core temperature. Altered mental status typically is not associated with heat exhaustion.1,2,4 The treatment of heat exhaustion is like the other milder forms of heat illness but with a greater effort on quickly cooling the athlete. Move the athlete to a cool area, preferably an air-conditioned room if one is nearby. Have the athlete lie down with legs and feet elevated and start drinking cold water or a cold electrolyte replacement drink. Remove excess clothing from the athlete and transfer athlete to a swirling ice immersion tub, if available, or wrap the athlete in an ice “taco” blanket or an ice sheet if an immersion bath is not available.1 Monitor the athlete closely for any increase in rectal temperature or the development of altered mental status as exertional heat exhaustion can progress into exertional heat stroke. Also, one should monitor vital signs closely since exertional heat exhaustion can mimic other developing diseases such as diabetes, cardiac disease, stroke, anxiety, migraine headaches or viral illness. While cooling the athlete, it is wise to arrange an emergency room transfer for further evaluation of the athlete.
As noted previously, EHS is a medical emergency. If it is not recognized urgently and treated appropriately, EHS can result in multiorgan system failure and even death of the athlete. EHS can have many of the signs and symptoms of heat exhaustion but will also have altered mental status and a core body temperature of equal or greater than 40.50 C or 1050 F.1,2 as measure with a rectal thermometer.1,2 EHS typically occurs in athletes engaging in extreme physical exertion in hot and humid conditions.1,2,4 EHS most commonly occurs at the beginning of the late summer or early fall sport season, especially in those athletes who have not acclimatized to intense exercise in the hot and humid climate of late summer.1,2 In treating EHS, the mandate is one has 30 minutes to decrease the athlete’s rectal temperature to below 38.90 C or 102.00 F to avoid multiple system failures.1 As with heat exhaustion, cooling in a swirling immersion ice bath is recommended. If not available, then using an ice “taco” type blanket wrap or an ice sheet to surround the athlete with an ice-cold environment is recommended. If the athlete is alert and can drink, have the athlete start drinking cold water or a cold electrolyte replacement drink. One should call 911, but in cases of EHS, the athlete should first be cooled until their temperature is below 38.90 C or 1020 before transport. The ambulance medics will then be on stand-by to transport the athlete urgently after initial cooling and to start intravenous fluids if needed. The emergency room to which the athlete will be transported should be notified, so they are prepared for the athlete after onsite cooling.
Those in charge of high school and college sport programs typically assume that many athletes who begin their preseason activities in August after summer break have not acclimatized to performing intense activity in hot and humid weather. Acclimatization is the result of physiologic adaptations to improve decreasing body heat in hot, humid conditions.4 Young children acclimatize slower than adolescents and adults.14 Acclimatization results in increased sweating, increased skin blood flow and stabilization of circulation in hot, humid conditions. Acclimatization in most people takes four-14 days of working out in the hot humid climate for at least two hours a day.3,9 Therefore, most high schools begin their return to sport programs in the late summer for athletes who play fall sports outdoors with a 14-day acclimatization program. In colleges, an acclimatization program may be five to seven days or longer depending on the environmental conditions. Frequent breaks in a shady area with plenty of cold water or electrolyte replacement drinks during this time should be liberally provided to the athletes. In sports with heavy gear, like football, initial practices should be without heavy gear and often in lightweight, light-colored clothing that wicks sweat away from the body. Over the time allotted for acclimatization, extra clothing and gear is slowly added while taking into consideration the environmental conditions. If the sport has practices twice daily, there should be enough time scheduled between practices for the athlete to rest, recover, and rehydrate from the first practice. Athletes should weigh in before each practice and weigh out after practice so make certain they are hydrating effectively.14 An example of practice guidelines during the acclimatization period as well as an example of guidelines for fluid management can be found in the article by Smith.4
Most sport programs use Wet Bulb Globe Temperature (WBGT) readings as a guide to alter time, duration and intensity of practices not only at the beginning of the season but also throughout the season. The WBGT is calculated from dry bulb globe temp (ambient temperature), wet bulb temperature (relative humidity) and globe temperature (radiant heat).1,2 There is a greater risk of EHI when the WBGT is greater than 82 degrees.4 Some state high school associations mandate at what WBGT sport must be cancelled.17 However, the WBGT does not take into account the metabolic heat produced by the exercising individual. The medical staff needs to factor in this parameter as well as the WBGT when determining time and intensity of activity for athletes on a hot, humid day. One should also remember that children produce a greater amount of metabolic heat for a given task compared to adults.13
Those in charge of athletes’ medical care should also be familiar with athletes who have a prior history of an EHI, sickle cell trait, diabetes, recent viral illness or other medical issues including medications such as antihistamines or attention-deficit/hyperactivity disorder medications that would make the athlete more prone to heat illnesses.9 These athletes will likely need extra monitoring and should report any signs of heat injury immediately.
The medical staff should develop an emergency treatment plan for EHI, like other plans for medical emergencies. This plan should be written, include a review of the signs and symptoms of EHI, and have a list of all equipment needed to treat athletes with EHI. This equipment must be taken to all practices and sporting events. It should include filled water immersion tanks or, if impossible to have filled immersion tanks, extra sheets, blankets, or tarps to make ice “taco tarps,” ice blankets, or sheets. Plenty of ice, water, and electrolyte-rich drinks need to be available. Essential equipment includes the following: a rectal thermometer, a blood pressure cuff, a pulse oximeter, access to the WBGT at the event site, the number of the ambulance service, and written directions to the site of the sporting event. Cold immersion tanks are mandated to be present in some states when the WGBT reaches a specified level.17
It’s important to make certain that cell phone service is available at the site of practices or games. If not, make certain that some form of communication with emergency services is available. This emergency plan, just like all emergency plans for the safety of the athlete, should be distributed to all on the sport staff, not just the medical staff, so everyone knows their responsibilities in an emergency situation. Remember: Education and proper preparation save lives!
References
1. Casa DJ, DeMartini JK, Bergeron MF, Csillan D, Eichner ER, Lopez RM, Ferrara MS, Miller KC, O’Connor F, Sawka MN, Yeargin SW. National Athletic Trainers’ Association Position Statement: Exertional Heat Illness. J Athl Train. 2015;50(9)986-1000.
2. American College of Sports Medicine, Armstrong LE, Casa DJ, Millard-Stafford M, Moran DS, Pyne SW, Roberts WO. American College of Sports Medicine position Stand: Exertional Heat Illness during Training and Competition. Med Sci Sports Exerc. 2007; 39(3):556-572.
3. Adam WM. Exertional Heat Stroke within Secondary School Athletics. Curr Sports Med Rep. 2019;18(4):149-153.
4. Smith MS, Prine BR, Smith K. Current Concepts in the Management of Exertional Heat Stroke in Athletes. Curr Orthop Pract. 2015;26(3)287-290.
5. Lipman GS, Gaudio FG, Eifling KP, Ellis MA, Otten EM, Grissom CK. Wilderness Medical Society Clinical Practice Guideline for the Prevention and Treatment of Heat Illness: 2019 Update. Wilderness Environ Med. 2019;30(4S);S33-S46.
6. Sorensen C, Hess J. Treatment and Prevention of Heat-Related Illness. N Engl J Med. 2022;387(15):1404-1413.
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11. Eichner ER. Exertional Rhabdomyolysis in Civilian and Military Populations. Curr Sports Med Rep. 2020;19(3):99-100.
12. Eichner ER. Suddenly, Last Summer: Heat Deaths of Athletes, Soldiers and Hikers. Curr Sports Med Rep. 2023;22(11):367-368.
13. American Academy of Pediatrics Committee on Sports Medicine and Fitness. Climatic Heat Stress and the Exercising Child and Adolescent. Pediatrics. 2000;106(01):158-159.
14. Poole JA, Stearns RL, Lopez RM. Heat Acclimatization and Exertional Heat Illness Prevention in Youth Football Programs. Strength Cond J. 2017; 39(2):69-70.
15. Szymanski M, Miller KC, O’Connor P, Hildebrandt L, Umberger L. Sweat Characteristics in Individuals With Varying Susceptibilities o Exercise-Associated Muscle Cramps. Strength Cond J. 2022;36(5);1171-1176.
16. Wilcox MJ, Rhodehouse BB, DeGroot DW. Ice Sheet Cooling in the Field Reduces Morbidity in Exertional Heat Stroke. Curr Sports Med Rep. 2024;23(4):119-123.
17. Georgia High School Association. By-Law 2.67-Pactice Policy for Heat and Humidity. https://www.ghsa.net