Keep Your Cool: A Runner's Guide to Heat and Hydration

Timing Is Everything
Early morning and late evening are the best times to run outdoors during hot days. Temperatures are almost always at their lowest right around sunrise, but humidity levels are typically much higher in the morning than later in the day. These two factors combine to create what's known as the heat index, which is a local measurement of the cumulative effect heat and humidity have on the body. Check your local weather report to find the heat index for various times throughout the day, and plan your outdoor runs accordingly. The National Oceanic and Atmospheric Administration warns that a heat index above 80 warrants caution, and exercising in a heat index above 90 is not advised.

Dress for the Occasion
Cotton absorbs your sweat and holds onto it, whereas other wicking fabrics, such as nylon and polyester blends, carry the moisture away from your body, allowing sweat to evaporate and keep you cool. For this reason, it's important to wear running gear that is lightweight, airy and wicking when the heat index is high. It might also be a good idea to wear a lightweight, breathable hat that will bounce the sun's rays off your head and keep you cooler.

Carry Plenty of Ice Water
Relying on public water supplies along trails or in parks could leave you high and dry, so if you're headed out for anything other than a short, easy run, it's important to take water with you. In addition to carrying fluid for rehydrating, it's a good idea to carry a bottle of cold ice water you can use to douse your head, neck and back periodically on very hot days. This can help keep your body temperature down if you start to overheat.

More: Improving Your Form Before You Take a Step

Know The Warning Signs
The best indicator of dehydration is thirst, but it can be tough to notice. If you're concentrating on things like your running pace or form, be sure to also check in with yourself every 15 minutes or so to determine your level of thirst. Muscle cramps and lightheadedness are more serious signs of dehydration, so if you begin to experience these symptoms, stop running and begin rehydrating immediately. Take slow, small sips of water and do not resume exercise for the remainder of the day.

Heat exhaustion and heat stroke are two dangerous conditions that can set in anytime your body overheats, even if you are well hydrated. It's tough to notice many of the usual symptoms (such as profuse sweating or cold, pale skin) when you're running, so be on the lookout for lightheadedness or nausea.

If you experience any of these indicators, you need to stop running immediately and cool your body's core temperature. Move into the shade or indoors, sit down and sip water slowly. If your heart rate doesn't return to normal within a few minutes, or if you vomit or feel faint, the condition is serious enough to warrant a call for immediate medical attention.

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About the Author

Rashelle Brown

Rashelle Brown is a Certified Personal Trainer and health coach who has been writing about health and fitness since 2010. Her work has appeared in IDEA Fitness Journal and on the popular health websites livestrong.com and eHow.com. She is a regular contributor for ACTIVE.com and nextavenue.org. Her first book, Reboot Your Body: Unlocking the Genetic Secrets to Permanent Weight Loss, is due out Aug. 25. Learn more at wellcuratedife.com.
Rashelle Brown is a Certified Personal Trainer and health coach who has been writing about health and fitness since 2010. Her work has appeared in IDEA Fitness Journal and on the popular health websites livestrong.com and eHow.com. She is a regular contributor for ACTIVE.com and nextavenue.org. Her first book, Reboot Your Body: Unlocking the Genetic Secrets to Permanent Weight Loss, is due out Aug. 25. Learn more at wellcuratedife.com.

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