Experts warn of danger of exercising in extreme heat and humidity

Extreme heat makes it especially hard for your body to cool down, so you need to be extra careful if you exercise or play sports when it’s baking outside.

Your brain tries to keep your body within a degree or two of 37 degrees Celsius, and it does so in part by triggering sweat. When sweat dries, it carries away heat from your body’s surface.

When sweat can’t do its job — because your body is generating a lot of heat or it’s too hot and humid to cool down — you are at risk of becoming dehydrated or even getting a heat-related illness such as heat exhaustion or heat stroke.

The higher the temperature, the harder it is for the body to stay cool, but humidity plays a big role too. High humidity makes it feel hotter than the temperature because it makes sweating less effective. There’s so much water in the air already that it can’t take up much more — including the water in your sweat.

The heat index, which factors in humidity and is included on many weather forecasts, provides a sense of how hot it really feels — and what’s dangerous for prolonged exposure or strenuous activity.

The National Oceanic and Atmospheric Administration says people should start exercising “caution” when the heat index reaches 26 to 32 degrees Celsius (80 to 90 degrees Fahrenheit) and “extreme caution” from 32 to 39.4 degrees (90 to 103 degrees Fahrenheit). It labels everything over 39.4 degrees Celsius (103 degrees Fahrenheit) “danger” or “extreme danger.”

NOAA has a chart that shows how the heat index is affected by humidity. For example, a day that is 32 degrees Celsius, or 90 degrees Fahrenheit, can hit the “danger” level with 70 percent humidity.

Exercising safely

If you want to exercise in the heat, here are some tips to say safe, according to the US Centers for Disease Control and Prevention.

— Time your exercise and outdoor activities for the coolest parts of the day.

— Try to exercise in the shade as much as possible.

— Take frequent breaks.

— Drink lots of fluids, and limit drinks that are high in sugar, caffeine and alcohol. Don’t wait until your are thirsty to drink more.

— Exercise with someone so you can check on each other, or pair up with a teammate.

If you start to feel any of these symptoms, stop exercising, get to a cool place and seek medical care:

— Muscle cramping or muscle weakness

— Shortness of breath

— Dizziness

— Headaches

— Nausea

If you take it too far, you are risk of heat related illnesses.

A common heat-related illness is heat exhaustion, which can be marked by rapid heartbeat, fast breathing, headache, nausea and muscle weakness or cramping.

It can develop into the more serious heat stroke, when your body can no longer control its temperature. Symptoms include confusion or slurred speech, seizures or even loss of consciousness.

Heat also increases your risk for a rare condition called rhabdomyolysis, which causes the rapid breakdown of muscles. If you think you or a fellow athlete are in danger, call emergency services, give them fluids — preferably water — and try to cool their bodies with cold water or cold compresses.