Especially in the summer, temperatures rise and heat-related illnesses become more common. It’s important to familiarize yourself with the signs of heat exhaustion so you can identify them when you or someone else may be in danger of a heat stroke. When exposing yourself to high temperatures and humidity, there are steps you can take to exercise safely in the heat.


Exercise-related Heat Exhaustion

Exercise-related heat exhaustion is an illness caused by getting too hot when you exercise. Exercising in hot weather puts extra stress on your body as both the air temperature and humidity increase your core body temperature during exercise. This condition happens when your body can no longer get rid of the extra heat made during exercise, and your body temperature rises more than is healthy. Not drinking enough fluids during exercise can also cause dehydration. Together, these things can make you collapse. In the U.S., exercise-related heat exhaustion is a common problem in athletes, especially football players and military recruits in basic training.


Your body has several ways to lower your body temperature when it gets too high such as sweating. When sweat evaporates, it lowers your temperature. But if the humidity is high, your body faces added stress because sweat doesn’t easily evaporate from your skin. In high humidity, your body can’t use sweat to cool itself, robbing your body of one of the most important ways of getting rid of extra heat.


Many other things can make it harder for your body to get rid of extra heat. These include:

  • Being in poor physical shape

  • Having an infection

  • Not being used to a hot environment

  • Taking certain medicines such as stimulants, antihistamines, and medicines for epilepsy

  • Having certain medical conditions, like sickle cell disease or conditions that decrease sweat

  • Having a chronic illness

  • Being dehydrated

  • Using alcohol before exercising

Adults over the age of 65 and young children along with women, people of white background, and people who grew up in more temperate climates may be more likely to get heat exhaustion when exercising in hot, humid conditions.


Your body can also lower the temperature by sending more blood to your skin and to circulate through your skin across your arms, legs, and head which lets more heat escape, leaving less blood for your muscles, which in turn increases your heart rate. However, once you stop perspiring in hot, humid conditions, you are at greater risk of dehydration, heat exhaustion, or heat stroke. If your body cannot get rid of the extra heat, your body temperature will rise. In heat exhaustion, your body temperature may rise to 101°F (38.3°C) to 104°F (40°C). This can make you feel weak and dizzy, and your heart may not be able to pump enough blood which can make you collapse.


Heat Exhaustion vs. Heat Stroke

Heat exhaustion is a milder form of heat-related illness that can develop after several days of prolonged exposure to high temperatures, and inadequate or unbalanced replacement of fluids from activities such as physical exertion. During heat exhaustion, your body temperature rises above normal, which your brain usually keeps within a degree or two of 98.6°F or 37°C. Unlike heat stroke, heat exhaustion does not cause significant brain or thinking problems, such as delirium, agitation, or unconsciousness or health complications, like damage to organs or brain. In some cases, your provider may run tests to check for these complications which may include:

  • Blood tests to look at electrolytes and check for infection

  • Blood and urine tests to see how well your kidneys and liver are working

  • Chest X-ray to check your lungs

  • Electrocardiogram (ECG) to check your heart rhythm

  • Drug panels to check for a medicine-related cause of high temperature

A healthcare provider trained in emergency care usually diagnoses heat exhaustion which might take place on the athletic field where you collapsed or at a hospital. These are common ways of treating heat exhaustion:

  • Stopping the activity and moving to a cooler area

  • Cool off until your temperature goes down. Oral thermometers and other ways to measure temperature are not accurate. Emergency medical personnel may measure temperature rectally. Until emergency medical personnel arrive, you should cool off until you shiver. This might involve soaking in cool water, spraying yourself with water, or sitting in front of a fan.

  • Drink water or a sports drink if you can drink, are not confused, and are not nauseated. If you are being treated at a hospital, the staff may give you IV (intravenous) fluids.

  • Monitoring your heart rate, blood pressure, breathing rate, and mental status.

  • Raising your legs to a level above your head

  • Taking off any extra clothing and equipment


Many people will show improvements within an hour or two of treatment. If you do not get better quickly, go to the emergency room where you will be checked for more serious problems. While on its own, heat exhaustion does not usually cause complications, if you have severe dehydration too, you may have problems like kidney damage or low blood pressure.


If left untreated, it may progress to heat stroke, the most serious heat-related illness, where body temperature may rise to 103°F or higher within 10 to 15 minutes and can stop basic processes in your body, causing serious problems such as:

  • Lung problems such as pulmonary edema or acute respiratory distress syndrome

  • Seizures

  • Muscle breakdown

  • Kidney injury

  • Liver injury

  • Blood clotting problems

  • Heart injury and heart failure

  • Death

Signs and symptoms may include:

  • Rapid heartbeat

  • Fast breathing

  • Fainting

  • Nausea, vomiting, or diarrhea

  • Headache

  • Heavy sweating

  • Dizziness

  • Mild, temporary confusion

  • Low blood pressure

  • Weakness

  • Muscle cramps

  • Dehydration

  • Problems coordinating movement

Seek medical treatment immediately if you experience these symptoms:

  • High body temperature

  • Altered mental state or behavior

  • Alteration in sweating

  • Nausea and vomiting

  • Flushed skin

  • Rapid breathing

  • Racing heart rate

  • Headache

The good news is that it’s often predictable and preventable. If you have heat exhaustion you should act quickly as temperature control is important because many processes in your body only work well within certain ranges. Unlike heat exhaustion, a heat stroke requires immediate medical attention and emergency treatment is required. Untreated heat stroke can quickly damage your brain, heart, kidneys and muscles. If you lose consciousness or continue to vomit, call 911. The damage worsens the longer treatment is delayed, increasing your risk of serious complications or death.


To prevent against heat-related illnesses, taking these actions may lower your risk:

  • Wear loose-fitting, lightweight clothing. Wearing excess clothing or ill -fitting clothing will prevent your body from cooling correctly.

  • Drink plenty of fluids.

  • Take extra precautions with certain medications. If you take medications that can affect your body’s ability to stay hydrated and react to heat, be careful.

  • Never leave anyone in a parked car. A common cause of heat-related deaths in children, when parked in the sun, the temperature in your car can rise 20 degrees Fahrenheit in 10 minutes! Even with the windows or shades down, avoid locking children in cars.

  • Take breaks and take it easy during the hottest parts of the day. Try to exercise in the early morning or late evening when it is generally cooler than the middle of the day.If you can’t avoid strenuous activity in hot weather, drink fluids and rest frequently in a cool spot.

  • Protect against sunburn. Wear a wide-brimmed hat and sunglasses and use a broad-spectrum sunscreen with SPF of 15 or higher. Apply sunscreen generously and reapply every two hours, or more often if swimming or sweating.

  • Get acclimated. People who are not used to hot weather are especially susceptible to heat-related illness so limit time spent working or exercising in heat until you’re conditioned to it as it can take several weeks for your body to adjust to hot weather.


Works Cited

Ansorge, Rick. “Heatstroke: Symptoms and Treatment.” WebMD, 11 Nov. 2020, Accessed 24 Aug. 2021.

Mayo Clinic Staff. “Heatstroke.” Mayoclinic, Accessed 24 Aug. 2021.

Wilson, Kristina. “5 Ways to Prevent Heatstroke.” Intermountain Healthcare, 20 June 2017, Accessed 24 Aug. 2021.

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