Safely Running In the Heat

By Rick Morris

If you are running in the heat, you must take steps to avoid heat related medical conditions. There are a number of serious conditions that can result from running in the heat, including heat exhaustion, heat stroke, dehydration and hyponatremia. These dangerous conditions can rear their ugly head at any time, but are especially dangerous when racing and your effort level is high.

Take steps to avoid these heat related illnesses and you will safely enjoy your running throughout the hot summer months.

The symptoms of hyponatremia include: nausea, muscle cramps, confusion, slurred speech, unsteady stride and disorientation. Because these symptoms mimic those of heat exhaustion, many runners make the mistake of increasing water consumption, which make the condition even worse. To avoid this, drink only sports drinks during events lasting longer that 1 hour.

Avoiding Trouble When Running in the Heat

  • If high temperatures are expected to be high, try to plan your workout for early in the morning when temperatures are at their lowest.
  • Drink a lot of fluid. Take in at least 6 to 12 oz. of fluid every 15 minutes. If your workout or race is going to last longer than 1 hour, drink a sports drink containing sodium, instead of water.
  • Wear a hat. A hat with a brim will keep much of the sun off of your head and face.
  • Wear sunscreen. Make sure you use a brand that is sweat proof.
  • Wear loose fitting, light colored clothing. Light colors will reflect some of the heat. There are a number of high-tech fabrics available that will wick the moisture away from your body and aid in cooling.
  • Warm up, rest and cool down in the shade. Direct sunlight can cause a rise in body temperature.
  • If you are planning a race in hot weather, try to get in at least two weeks of training in similar weather. This will help acclimate your body to the higher temperatures.
  • Check your urine color. If your urine becomes dark, you are dehydrated.


Dehydration is the most common heat related illness. Many individuals are in a constant state of dehydration because they simply do not drink enough water during the day. Drinking coffee, soft drinks, tea and alcohol can also contribute to dehydration. Dehydration is not limited to hot weather. You can become dehydrated at anytime of the year, but it is most common during warm weather.

The warning signs of dehydration include: dark yellow urine, decreased urination, loss of appetite and muscle cramps. More sever dehydration can result in nausea, dizziness or feeling lightheaded, fatigue, irritability and lack of concentration.

The average person needs 8 to 12 eight ounce cups of water per day. An athlete needs more. An active runner should be drinking at least 80 to 100 ounces of water per day. Runners need to drink fluids all day, not just during their workout or race. Thirst is not a good indicator of hydration levels. If you wait until you are thirsty to drink, you are probably already dehydrated!

To ensure proper hydration, drink 2 to 3 cups of fluids up until ½ hour before your race or workout. Drink another 8 to 12 ounces immediately before you start the activity. During your race or workout, drink 6 to 12 ounces of water or sports drink every 15 minutes. If your activity is going to last more than 1 hour, drink a sports drink instead of water. While you must maintain a proper hydration level be careful not to over hydrate.

It is important to replace lost fluids immediately following your activity. Research has indicated that you should drink at least 20 to 24 ounces of fluid for every pound of body weight that was lost. Most of us won’t have a scale available, so as a rule of thumb, drink 16 to 24 ounces for every 30 minutes of your activity. Sports drinks are a better choice than water for after-exercise hydration. The sports drinks contain both carbohydrates and sodium, which will aid in your recovery and in restoring lost electrolytes.

Heat Related Illness

There are three primary heat related illnesses. They are, in order of seriousness: heat cramps, heat exhaustion and heat stroke.

Heat Cramps

Heat cramps are cause by dehydration and a loss of minerals. This is not a life threatening illness, but can be very painful. The symptoms are cramping muscles, usually in the calf muscles, but can occur in other muscles. By the time heat cramps occur, you are already dehydrated. You should not continue to run because you will not be able to rehydrate yourself during your run. Drink a lot of sports drinks immediately. Massage the cramping muscles. Try to find some cool water or cool towels to cool your body and move out of the sun to a shaded or air conditioned location.

Heat Exhaustion

This condition is potentially very serious. Left untreated it could lead to heat stroke. Symptoms include nausea, dizziness, goose bumps, extreme fatigue, weakness, weak and rapid pulse, heavy sweating, uncoordinated stride or vomiting. If you suspect heat exhaustion you must stop running and seek medical attention. Lie down in a cool and shaded spot with your feet elevated. Drink a lot of sports fluids. Try to cool your body with cold water or cold towels.

Heat Stroke

The most dangerous hazard when running in the heat is heat stroke. Heat stroke is extremely serious and can even be fatal. If the symptoms of heat exhaustion are ignored, heat stroke is very often the next step. This condition involves a breakdown of the system that regulates your body temperature. Symptoms include all of the symptoms of heat exhaustion plus: disorientation, lack of consciousness, coma, high body temperature and bizarre behavior. Heavy sweating may be present, but usually heat stroke is accompanied by lack of sweating.

Heat stroke requires immediate medical attention. The runner suffering from heat stroke many times will be mentally incapacitated or unconscious, so many times, bystanders must assist the ill runner. A person suffering from heat stroke should be moved to a cool, shady spot and cooled with towels soaked in cold water or ice until medical help arrives. If the runner is conscious, large amounts of sports fluids should be consumed. Medical personnel will probably administer fluids intravenously.


Hyponatremia is literally water poisoning. Running in the heat requires hydration, but not over hydration. Most runners are not aware that they can drink too much water. Not only can you drink too much water, but it can also cause a very serious condition and has even caused some fatalities.

A low level of sodium in the blood causes Hyponatremia. When you sweat you lose approximately 2.25 to 3.4 grams of sodium per liter of sweat. During a race, you will average around 1 liter of sweat loss per hour. If you drink only water during your race, you will dilute your blood even more, which can result in hyponatremia. This condition is usually only a problem in activities lasting more than one hour, but can occur in shorter activities.

Hyponatremia can be a serious condition. If you believe you may be suffering from this illness, seek medical attention. Drinking sports drinks and eating salty foods can treat minor symptoms.

Aspirin, ibuprofen and other anti-inflammatory drugs can contribute to the development of hyponatremia. Because of the popularity of these medications among runners, this condition is becoming more prevalent, especially in the longer distances such as marathons, ultra-marathons and triathlons.

To avoid hyponatremia when running in the heat, follow these suggestions.

  • Drink sports drinks during events lasting longer than 1 hour.
  • Avoid anti-inflammatory medications.
  • Take in at least 1 gram of sodium per hour.
  • Drink at least 6 to 12 ounces of sports drinks every 15 minutes.
  • Increase you salt intake before your race.