You’re running at a steady pace, you have just hit your stride and you’re feeling limitless -- then you get the chills. Your instincts tell you that you’re cold, but it’s warm out. These “runner’s chills” are your body’s natural defense against overheating. Continuing to push through them can be dangerous. Once chills develop, there are immediate steps you should take to prevent heat stroke and/or dehydration.
Causes of Runner's Chills
Chills occur while running in high temperatures and humid weather. According to researchers with Runner’s World, your sweat evaporates and, subsequently, regulates your core body temperature; however, when dehydration, climate or other factors interfere with your body's natural perspiration response, you experience a state of stress similar to having a fever. As your core temperature continues to rise, you will begin to notice goose bumps and chills.
Chills are a warning sign from your body, and if you're experiencing these chills it's best to stop running immediately. According to Dr. Cathy Fieseler from Runner's World, walking is acceptable as an active cool-down, as long as no other symptoms of heat injury, such as dizziness or vomiting, occur. If you are still experiencing chills or other symptoms while you walk, you should find a safe, shady place to sit down and drink plenty of water or electrolyte-infused drinks. Finally, you should wait until the symptoms subside before attempting to venture back into the sun, and call off the rest of your run for the day.
When to See Your Doctor
Heat injuries, such as heat exhaustion or heat stroke, can be life threatening. If you frequently experience chills while running, then it's time to talk with your doctor about the safety of continuing to pursue that activity. It may also be necessary to seek medical attention if your chills are accompanied by other signs of heat injury, like confusion, dry skin, dizziness, cramping, nausea and/or headaches.
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Wearing light-weight clothing helps you remain cool during runs. Plan your route ahead of time so you pass community water fountains, or use a hydration belt on hot days. For runs longer than five miles, you should drink 15 ounces of water prior to running and again every 20 minutes while running to help prevent dehydration. Finally, choose to run early in the morning or late in the evening during warmer weather. Take precautions to guard against heat stroke and heed your body’s warning signal -- the chills. Taking action if the chills do set in can help prevent more serious issues from occurring.
Ari Reid has a bachelor's degree in biology (behavior) and a master's in wildlife ecology. When Reid is not training to run marathons, she is operating a non-profit animal rescue organization. Reid has been writing web content for science, health and fitness blogs since 2008.