Heat illness warning signs for runners: when to stop
Short answer: stop at the first sign of heat exhaustion: heavy sweating, weakness, dizziness, nausea, headache, or chills in the heat. Get into shade, cool down, sip water. Confusion, slurred speech or collapse is heat stroke: call 911 and start cooling the person immediately.
Heat cramps #
Signs: painful spasms in the calves, thighs or stomach, with heavy sweating.
Do: stop, get out of the sun, stretch gently, drink water or a sports drink. Cramps can mean heat exhaustion is next.
Heat exhaustion #
Signs: heavy sweating; weakness; cool, pale, clammy skin; fast, weak pulse; cramps; dizziness; nausea or vomiting; headache; fainting. Chills or goosebumps while hot.
Do:
- Stop. Get to shade or air conditioning.
- Loosen or remove extra clothing.
- Cool the skin: cold wet cloths, a cold shower or a cool bath.
- Sip water or a sports drink.
- Get medical help if you vomit, it gets worse, or it lasts over an hour.
Heat stroke: an emergency #
Signs: confusion, slurred speech, odd behavior, stumbling, collapse or seizures; throbbing headache; body temperature above about 103°F; hot, red skin that may still be sweaty; rapid, strong pulse. Don't wait for dry skin: during exercise, people with heat stroke often still sweat.
Do:
- Call 911. Delay can be fatal.
- Cool them now. Best: immerse the body in cold or ice water up to the neck. Otherwise: shade, soak them with cold water, and put ice or cold wet towels on the neck, armpits and groin, swapping them as they warm.
- No fluids if they're confused or unconscious.
- Fanning helps in moderate heat; above a heat index in the high 90s it can blow hotter air onto them.
Too much water: hyponatremia #
Signs: worsening headache, nausea, bloating or swollen hands and feet, confusion, seizures, usually after hours of drinking plain water. It's an emergency, and more water makes it worse. Prevent it: drink to thirst and take salt past an hour.
Higher risk #
- Your first hot weeks, or a trip somewhere hotter.
- Races and hard workouts, which make far more heat than easy runs.
- Recent illness, short sleep, alcohol.
- Some blood pressure, allergy and mood medications. Ask a pharmacist.
Prevention is mostly pacing: how to run in the heat and how much to slow down.
Questions #
What are the first signs of heat exhaustion while running?
Heavy sweating, weakness, dizziness, nausea, headache, and cool, clammy skin. Chills or goosebumps in the heat are a warning too.
How do you tell heat exhaustion from heat stroke?
Confusion. Heat exhaustion leaves you clear-headed; heat stroke causes confusion, slurred speech, odd behavior or collapse, with a body temperature above about 103°F. The skin may still be sweaty.
What do you do for heat stroke?
Call 911 and cool the person immediately: cold-water immersion if possible, otherwise soak them and put ice or cold wet towels on the neck, armpits and groin. No fluids if they're confused.
Can you drink too much water on a run?
Yes. Far more plain water than you sweat can dilute blood sodium (hyponatremia): worsening headache, nausea, swelling, confusion. It's an emergency; don't give more water.
Sources #
Related guides
ArcPace scores every hour of your forecast 0–100, with the pace cost at your easy pace and what to wear. Free for iPhone. Get it on the App Store