How Can I Stay Cool When I'm Running in the Heat?

Take these steps to stay safe and healthy during your summer runs.

Monday, August 6, 2012, 12:00 am

I barely sweat, if at all. This summer will be my first summer of running and I’m concerned about overheating. I normally run in the evenings during the week and mornings on weekends. Should I adjust my running to compensate for my body’s lack of cool down capabilities?




Welcome to summer time running! You are smart to be concerned about running in the heat. Sweating is the body's way of cooling itself, so it is very important that runners are able to sweat. If your body cannot adequately cool itself down, you are at great risk for developing heat illness. While there certainly are some medical conditions that impair sweating, since you say that you can sweat some, it is possible that training in the summer heat will increase your sweating capabilities. In the summer, all runners should take precaution and adjust their training based on the weather. It's best to avoid training during the hottest part of the day and run when it's cooler, like early in the morning or later in the evening, and, if necessary, there's always running indoors on a treadmill.

We are designed to maintain a constant core body temperature that is ideal for the many biochemical reactions that must occur within our body to ensure survival. Most of the time, our body temperature changes very little throughout any given day. The biochemical reactions our body depends upon take place at certain rates and these rates are dependent upon normal enzyme functioning. So what happens when we go for a run?

In order to run, our skeletal muscles must contract. Muscle contractions produce heat and this heat increases the body's temperature. The amount of heat produced is directly related to the amount of muscular work being done. Simply put, this means that larger runners and faster runners produce more heat than smaller runners or slower runners. Also, the faster the pace, the more heat generated due to a larger number of muscle fibers being recruited. So a large, muscular runner running at a fast pace will produce more heat than a small, lightly muscled runner running at a very slow pace. However, whatever amount of heat is generated by the runner, is also the same amount of heat that must be lost from that runner, a perfect example of homeostasis at work!

So how do we lose the heat we generate? An increase in body temperature triggers the hypothalamus to signal the sweat glands and the blood vessels of the skin to promote heat loss. Blood flow is directed away from the body's core and sent to the skin's surface. At the skin's surface, blood passes through dilated blood vessels where the blood is able to dissipate its' heat to the skin and the blood cools down. As blood transfers its heat to the skin, the skin uses evaporation to cool off and so we sweat. As sweat evaporates, the body is cooled. While running in the heat, blood flow to the surface of the skin can be so high and blood vessels so dilated, that the skin can become blotchy or take on a reddish hue due to this change in circulation. Sweat production increases by volume and by rate. This is why proper hydration becomes critical. Drinking plenty of water and sports drink to replace fluids and electrolytes lost in sweating needs to become a daily routine in the summer.

High temperatures and high humidity are the worst conditions for a runner because this combination makes it difficult for the body to dissipate heat. As the temperatures and humidity climb throughout the summer, it becomes increasingly important to be prepared for tough conditions. While we cannot control the weather, we can control our hydration, electrolyte intake, and our training, so here are more tips for running in the heat.

Tips for Running in the Heat:

  1. Avoid the hottest part of the day. Train early morning or late in the day.
  2. Adjust your run pace based on weather conditions. The hotter it is, the more humid it is, the slower the run pace. Use perceived exertion and/or your heart rate as your guide, not your run pace.
  3. Increase fluid intake throughout the day, every day.
  4. Add sports drinks that contain electrolytes to your fluid intake. Avoid washing electrolytes out with more fluid intake.
  5. Find running routes with water sources.
  6. Wear light colored, loose fitting clothing.
  7. Be flexible with your workouts. Adjust the distance as necessary.
  8. Pay attention to how you feel. Watch for signs of heat illness like dizziness, nausea, or fatigue. Stop running and seek help.
  9. Run with a partner, if possible. If not, always let someone know your route and when you expect to return.
  10. Some medications are not compatible with running in the heat. If possible, time taking any medications around your run.


Proceed very cautiously with your training using these tips on running in the heat. Try some shorter runs to see if your body responds. Make sure you are well hydrated and that water is available during your run. If you find you are sweating some, gradually extend your distance. If your body does not respond well to heat acclimation, then consider running indoors on a treadmill to be safe. This will be important information for you to know about yourself as you pick and choose your races since favorable weather conditions will be of critical importance to you.

All the best!

Susan S. Paul, MS

Susan Paul has coached more than 2,000 runners and is an exercise physiologist and program director for the Orlando Trach Shack Foundation. For more information, visit

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