Games in Manaus, Brazil, a city along the famous Amazon River, have been played in temperatures in the high 80’s and humidity levels approaching 70%. This makes for very difficult playing conditions, and TV images of highly conditioned athletes cramping late in a game have been plentiful. Show Even NBA basketball fans have seen the effects of high heat and humidity. During the NBA Finals in San Antonio the arena’s air conditioning went out and temperatures neared 90 degrees. By the fourth quarter, at a very critical point of the game, Miami Heat star LeBron James was forced to the sidelines by debilitating cramps. High heat and humidity lead to two problems in the exercising body: 1) increased core body temperature and 2) dehydration. Increased body temperature (hyperthermia) leads to decreased muscle endurance, which means the muscle’s ability to contract repeatedly or in a sustained manner over long periods of time. High core temps also cause a shift in energy production from aerobic to anaerobic mechanisms, which means the body has to use up its muscle energy stores more rapidly. Unfortunately, during a longer athletic event, the rate of adding energy (sports drinks, energy bars, gels, etc) can’t keep up with the rate of losing energy when heat and humidity are high. Finally, high body temperature causes a decrease in blood flow to the heart as blood pools in the limbs. If the heart doesn’t get as much blood, it can’t pump as much oxygenated blood back to the muscles. Dehydration often occurs long before some athletes realize it or before cramps set in. Athletes can lose as much as 2 to 8 % of their body weight during high intensity exercise, and the rate of fluid absorption from the gut just can’t keep up with that rate of loss. Dehydration causes a decrease in VO2max, which means the body can’t utilize oxygen as efficiently to provide energy. Dehydration also contributes to the decrease of heart blood pumping mentioned above. So what can be done to combat or prevent the effects of high heat and humidity? If you paid attention to news reports building up to the start of the World Cup, you heard about teams from all over the world flying to places with higher heat and humidity to train. Several teams trained in Miami, some in Latin America, and a few went right to Brazil. Acclimatization to higher temps and humidity can occur fairly quickly, as quickly as 7-10 days. Another prevention for heat/humidity effects is conditioning. Better-conditioned athletes suffer less performance loss in high heat and humidity because they have a higher blood volume, better VO2max, sweat rate and more efficient use/replacement of energy stores. World Cup athletes have been training for several months (in addition to playing in their normal club/team roles) in preparation for this major event. Fluid replacement is critical for events in high heat and humidity. Fluid replacement starts before an event, continues during it, and doesn’t stop until long afterwards. Drinking to thirst and keeping urine clear (not dark yellow) are good measures. Wearing light-weight, light-colored clothes of open-weave natural fibers (cotton, wool) or fluid-wicking fibers help increase evaporation and cool the body. Even here in Utah where the humidity is low, we’re susceptible to heat-related performance drop or even heat illness if we’re not careful. Be smart and enjoy the sun. Then, after a great, hot workout, find a cool drink and a TV positioned right below a soothing fan to enjoy some incredible World Cup matches!
Hyperthermia is an abnormally high body temperature. Also called heat illnesses, there are several forms of hyperthermia. Heat cramps are fairly mild, whereas heat exhaustion is more severe. Heatstroke is the most serious form of hyperthermia and can be life-threatening.
Hyperthermia is an abnormally high body temperature — or overheating. It's the opposite of hypothermia, when your body is too cold. Hyperthermia occurs when your body absorbs or generates more heat than it can release. A human’s normal body temperature is about 98.6 degrees Fahrenheit. Any body temperature above 99 or 100 degrees Fahrenheit is too warm. Hyperthermia is usually the result of overexertion in hot, humid conditions. Most forms of hyperthermia are preventable. Is hyperthermia the same as a fever?Hyperthermia isn’t the same as a fever. When you have hyperthermia, your body temperature rises above a certain “set-point” that’s controlled by your hypothalamus (a part of your brain that controls many body functions). But when you have a fever, your hypothalamus actually increases your body’s set-point temperature. This intentional rise in body temperature is your body’s attempt to fight off an illness or infection. Are there different types of hyperthermia?Hyperthermia describes a group of heat illnesses that include (from least to most severe):
What is malignant hyperthermia?Malignant hyperthermia is a genetic condition that can make you susceptible to hyperthermia if you receive a specific combination of sedatives and anesthesia for medical procedures. If you have this disease, your body temperature can spike dangerously during or after surgery. People with malignant hyperthermia might have a reaction the first time they’re exposed to certain medications, but it’s more common after several exposures. Who gets hyperthermia?Anyone can get a heat illness, but you’re at especially high risk if you:
How common is hyperthermia?Between 2004 and 2018, an average of 702 heat-related deaths occurred in the U.S. each year. Athletes, outdoor laborers, military trainees, infants and the elderly are the most likely to develop hyperthermia. Heat exhaustion is a type of hyperthermia characterized by blurred vision, dizziness, low blood pressure and other symptoms. Hyperthermia occurs when your body takes in more heat than it releases. Sweat is your body’s natural cooling mechanism, but sometimes sweating isn’t sufficient to keep your body at a normal temperature. When this happens, your body temperature can rise. Physical exertion in very hot, humid weather is the most common cause of hyperthermia. What are the symptoms of hyperthermia?Heat cramps typically cause sudden muscle spasms in your feet, calves, thighs, hands or arms. The cramps might feel painful or tense. Your muscles might be sore after the cramp passes. Symptoms of heat exhaustion include: Symptoms of heatstroke can often be similar to those of heat exhaustion, but may also include: People with heatstroke can develop shock, slip into a coma, experience organ failure or die. If you experience symptoms of heat stroke, seek immediate medical attention.
Healthcare providers diagnose hyperthermia by reviewing your symptoms, performing a physical exam and taking your temperature. They may also order blood or urine tests.
If you experience mild-to-moderate heat illness symptoms, you should:
You can usually treat these conditions at home. In some cases, your healthcare provider may recommend intravenous (IV) fluid replacement through a catheter in your arm. How is heatstroke treated?Heatstroke is a medical emergency that requires treatment in a hospital. If you’re waiting for an ambulance to arrive, try to cool the person as much as possible:
At the hospital, you may receive cooled IV fluids. A healthcare provider may also recommend cold-water lavage. This is a procedure that washes out body cavities with cold water.
In most cases, it’s possible to prevent hyperthermia. You should:
If you must do activities in the heat due to your job or a sport, let your body gradually acclimate to the heat. Start doing light work or exercise about two weeks before you need to do the really hard work. Then, gradually build your body’s ability to withstand high temperatures. If possible, plan to do the work during the early morning hours when it might be cooler.
Most people recover fully from heat illnesses once they rest in a cool environment and replace lost electrolytes. But heatstroke can lead to permanent organ damage or even death.
Contact your doctor if you or someone else:
A note from Cleveland Clinic Hyperthermia, or heat illness, is an abnormally high body temperature. It’s usually the result of doing too much physical activity in hot, humid weather. Infants, the elderly, athletes and people with strenuous outdoor occupations are at the highest risk for hyperthermia. Heat illnesses can range from mild (heat cramps or heat exhaustion) to severe (heatstroke). People with a heat illness should cool their body temperature right away. Call 911 immediately at the first signs of heatstroke.
Last reviewed by a Cleveland Clinic medical professional on 11/19/2021. References
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy |