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Some elements about running are rather universal amongst runners: The euphoric feeling of achieving a major personal record, the excitement felt when opening a new pair of your favorite running shoes, the lead-like weight of your legs over the last lap of a mile race or at the end of your hardest workout, and the joy that is going for a run on the most picture-perfect spring or fall day when the weather is just glorious and ideal for miles and miles of comfortable running. While all of us can probably conjure up a fond memory of one of those perfect weather days where we felt nearly weightless and invincible on our run, as if our ear-to-ear grin spread throughout our entire body, we all can probably recall a run where the blazing summer sun and heavy, humid air had us so overheated and parched that it felt like we were trudging through sludge and may never make it home. Though we all may wish to forget those sticky, summer runs where you struggle so much that you question your level of fitness, they can be somewhat inevitable, depending on where you live and the typical climate.
With some acclimating, purposeful dressing, additional hydration, and careful route planning, summer running can be totally workable and completely safe; however, an unfortunately high percentage of runners experience heat exhaustion at least once. Unlike just the typical minor discomfort and perhaps dip in running performance you might experience on any run in the heat, heat exhaustion is an adverse medical condition that develops when your body is unable to effectively cool down, causing your body temperature rises to unhealthy levels. If not treated and reversed quickly, it can escalate to heat stroke, which is a medical emergency.
While we all like to regale stories of challenging runs, there’s absolutely no glory to seek or rite of passage earned by battling heat exhaustion on the run. It’s important to know how to run safely in heat, the warning signs of heat illnesses, and how to treat heat exhaustion and heat stroke should you or one of your running buddies start to suffer.
Why Are Runners Prone to Heat Exhaustion?
Heat exhaustion is a condition where the core temperature gets too high, resulting in heavy sweating, a rapid heart rate, dizziness, and other symptoms. Though heat exhaustion and more serious heat illnesses can occur anytime you’re subjected to extreme heat and/or humidity, the risk of heat exhaustion increases when running in the heat, due to the natural increase in core body temperature that occurs when exercising. One of the primary ways the body normally cools down is by increasing blood flow to the relatively cooler skin. When you run, your body generates additional heat, and instead of diverting as much as possible to the skin, blood flow is mostly routed to your working muscles, which can cause the body to overheat.
Dr. Cordelia W. Carter, MD, associate professor of orthopedic surgery and director of women’s sports at NYU Langone Health adds that runners are more prone to heat exhaustion while running because they can become dehydrated. “Typically, long periods of exertion (particularly in hot, humid, sunny conditions) may lead to significant losses of water and electrolytes through sweat,” she says. Dehydration contributes to developing heat exhaustion, which is why staying properly hydrated before and during your run is key.
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Symptoms of Heat Exhaustion in Runners
Knowing the signs and symptoms of heat exhaustion can save you and your running companions from more dire situations and severe heat illnesses. It’s important to note that you certainly don’t need to be presenting with all of the listed symptoms to be suffering from heat exhaustion; each runner may present with heat exhaustion differently. It’s always best to err on the side of caution, immediately stop running, and begin taking steps to lower the body temperature. The defining symptom of heat exhaustion is a body temperature of 101°F (38.3°C) to 104°F (40°C). However, since it’s unlikely you have a thermometer tucked alongside your gel packet in the pocket of your running shorts, the following are additional signs and symptoms of heat exhaustion:
- Rapid heart rate
- Rapid breath rate
- Excessive sweating
- Muscle cramps
- Clammy or damp skin
- Excessive thirst
- Difficulty coordinating body movements
- Low blood pressure
As may be evident from this list, identifying heat exhaustion symptoms in runners can be confounded by the normal physiological responses to running in general. For example, we all know running increases heart rate, breath rate, and sweating, so teasing out the “normal” increases when you’re running versus a distress sign of heat exhaustion can be difficult. In general, proceed cautiously if you think your body’s responses seem at all exaggerated (like you’re sweating more than normal in that weather, or your heart seems to be beating faster than seems warranted at that effort and pace), begin treating the situation as if it’s definitely a heat illness.
Lastly, it’s important to note that someone experiencing heat exhaustion typically does not experience significant cognitive symptoms, though some mild confusion may be present. However, any signs of mental distress should be taken as extreme warning signs for the more serious heat illness: heat stroke. Heat stroke, which is defined as a body temperature greater than 104°F, is a medical emergency and requires immediate emergency medical care. With heat stroke, there might be further confusion, delirium, difficulty thinking and concentrating, agitation, memory issues, loss of consciousness, and even coma. Additionally, while most of the rest of the symptoms of heat stroke overlap with those of heat exhaustion, there is usually a stark absence of sweating, accompanied by red, hot skin with heat stroke whereas someone with heat exhaustion is still sweating.
Risk Factors for Developing Heat Exhaustion
Of course, the risk of developing heat exhaustion when running is correlated with increasing temperature, but it’s actually the heat index—or the “feels like” temperature, which considers both the air temperature and the relative humidity together—that matters most. For example, if it’s 85 degrees with 60 percent humidity, the heat index is 90 degrees. That same temperature with humidity at 90 percent has a heat index of 101 degrees. Online charts can show you the calculated heat index along with the graded risk level for developing a heat-related illness.
Besides the typical environmental conditions like high temperatures, high humidity, and/or direct sunlight, there are a several factors that can increase the risk of developing heat exhaustion when running, including the following:
- Dehydration and not drinking enough fluid before and during your run.
- Wearing too many clothes, fabrics that don’t breathe, or dark colors.
- Drinking alcohol before running.
- Having a chronic illness or certain medical conditions.
- Not being acclimated to running in the heat and humidity.
- Being in poor physical shape.
- Being obese or significantly overweight.
- Taking certain medications like antihistamines and stimulants.
- Being very young or an older adult because thermoregulation isn’t as effective.
How to Prevent Heat Exhaustion When Running
Like many truths in life, prevention is ultimately the best management strategy for heat exhaustion. Fortunately, while facing hotter, humid runs is likely an inevitable part of summer running depending on where in the world you enjoy your weekly miles, there are several precautions you can take to help mitigate the risk of developing heat exhaustion when running.
Allow your body time to acclimate to the heat.
Most exercise physiologists agree that it takes about two weeks for your body to acclimate to running in a hotter environment. Be patient with yourself and adjust your workouts as needed while your body is adjusting to the added stress of running in the heat and humidity.
Adjust your goals.
It’s simply a scientific fact based on human physiology that your physical performance declines when it’s hot and humid. Accordingly, it’s unreasonable to expect yourself to nail split times and maintain the paces you can hit under more reasonable weather. This is another reason why focusing on effort is more important than running pace in the heat.
Run by effort, not by pace.
If you’re a runner who loves checking your watch and sets target paces for every run, you’re certainly not alone. As runners, we tend to love feeling like our training is precise as possible, and that often involves nailing certain paces and splits. However, summer running, or days when it feels like a greenhouse outside, are often better served by running by feel, using effort and not pace to guide your workout. Not only are you less likely to hit specific paces in the heat, but you’re also more likely to ignore heat exhaustion cues from your body. When you run by feel, you listen to your body, honoring its needs while still getting a quality workout.
Run before the sun rises or after it sets.
Though some summer days are hot and muggy from dusk through nightfall, avoiding sunlit hours will at least remove the additional heat from a scorching sun.
Hydrate enough before and during your run.
Staying well hydrated is crucial for staving off the dehydration that contributes to heat exhaustion when running. Depending on your sweat rate and the environmental conditions, aim to drink 4-8 fluid ounces of water or electrolyte-infused sports drink every 15-20 minutes during your run. The goal is to hydrate on pace with the fluid you lose through sweat such that your weight on the scale after you run is within a pound or two of your weight before you head out the door. If it’s not, adjust your hydration plan moving forward, keeping in mind that you need to drink an additional 16 ounces for every pound lost.
Find the shade.
Dark-colored asphalt radiates heat, adding to the cloud of hot air you’re running through. Trails are a great option for summer miles because they are usually shaded from the natural canopy of the trees. Bike paths and rail trails are often more sheltered from direct sunlight as well.
Wear light-colored, breathable clothing.
Anyone who’s dragged themselves out on a frigid winter morning with enough layers to outfit a small team, only to find yourself soaking wet and overheated knows that dressing appropriately is sometimes what differentiates a successful run and a miserable slog. The same principle applies to summer running, though obviously the inverse. Wear light-colored, lightweight, breathable fabrics for your hot-weather runs, and as little clothing as you’re comfortable wearing (or is appropriate). Remember that dark colors absorb heat from the sun. It’s also a good idea to wear a visor and running sunglasses to keep the sun off your face and out of your eyes while still permitting heat to escape from the top of your head.
Shift your training schedule.
If the long run or hard workout your training schedule calls for happens to land during a heat wave or dreadfully humid day, see if you can shuffle some workouts around so that your rest day coincides with the least favorable weather conditions and your tough workouts fall on tolerable days.
Douse yourself in water.
Do you remember the joy of running through a sprinkler when you were a kid? Relive those days by darting through sprinklers or pouring water over your head and inner wrists at every water fountain you pass. If your run takes you past a safe body of water you’re allowed to enter, jump in before or halfway through your run to lower your body temperature. Alternatively, soak a bandana in ice water at home and tie it around your neck before you head out for your run.
While you may be one of those runners who has dubbed the treadmill the “dreadmill,” taking your run indoors to an air conditioned space with a treadmill is advisable whenever the heat index is considered at an elevated risk for developing heat exhaustion. Hey, it beats canceling the run altogether.
How to Treat Heat Exhaustion When Running
Dr. Carter says that if despite your best efforts, you or one of the running buddies with you develops heat exhaustion while you are running, the immediate treatment goals are to cool and hydrate the affected runner. “If the runner is conscious and able to drink (not too disoriented or vomiting), then first steps are: Find shade and/or air-conditioning; shed extra layers of clothing; consider a cool bath (this is first-line treatment for heat stroke); sit and/or lie down and elevate the feet; and drink fluids (water and/or electrolyte-replacement drinks like popular sports drinks or coconut water),” she says. “If symptoms are more severe (the runner is extremely disoriented, unconscious, seizing, or vomiting uncontrollably), this raises concern for more severe heat illness and emergency medical services should be contacted.”
Dr. Carter further explains that if indeed a more severe heat illness, such as heat stroke, is suspected, it’s crucial to escalate your treatment efforts while waiting for the ambulance to arrive. “While waiting for EMS to arrive, cooling as quickly as possible with an ice bath or cold towels is essential, and having runners lie down with the feet up and turning vomiting runners on their sides to prevent aspiration [should] also be done.”
You don’t have to know the specific classification of the heat illness in the moment to determine if medical attention is necessary; simply pay attention to certain warning signs. “Runners who are disoriented and remain so despite moving to a cool area and attempting hydration; those who are unable to keep fluids down due to vomiting; those who are unconscious and/or seizing, and those who have a temperature greater than 104 degrees F (if you have a thermometer handy) require immediate attempts at cooling and rapid medical attention,” says Dr. Carter.
As much as we all love running, when it comes to the dog days of summer, it’s always smarter to modify your training and ease up in the heat than find yourself rapidly spiraling into heat exhaustion.
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