Exercising outdoors packs many science-backed benefits: increased energy, improved mood, and reduced tension—but when temperatures soar, outdoor workouts can make you fizzle. In hot weather, your heart not only pumps blood to your working muscles but also sends blood to your skin so your body can release internal heat into the environment and help cool itself. This double duty puts added stress on your cardiovascular system, says Lawrence Armstrong, Ph.D., lead author of the American College of Sports Medicine’s position statement on heat and exercise. Staying in that state too long increases your risk for dehydration and heat-related illnesses. Not to worry, these strategies from top athletes and experts will help you beat the heat during your summer workouts.
Dial it Down
Your internal body temp rises as you exercise
harder and longer. So the best way to avoid overheating is to reduce your intensity or duration (or both), says Michael F. Bergeron, Ph.D., director of the National Youth Sports Health & Safety Institute. Your workout should feel just as difficult as it would on a normal day—not harder. Because heat and dehydration increase your heart rate faster, you’ll reach your usual intensity at a slower pace or after fewer repetitions, says Evan Johnson, a kinesiology doctoral candidate at the University of Connecticut.
Determining when and how much to cut back depends on the conditions (see “Weather Alert,” tip), your fitness level (new exercisers should stick to low-intensity workouts like walking), and how long you’ve been exposed to the heat (it usually takes two weeks to acclimate fully to hot temps). Listen to your body: If you’re hot or tired, take a break in the shade or wrap up early.
A 125-pound woman can sweat out up to two pounds of water
during a hot, hour-long run. “To sidestep fatigue during your workout, you should be consuming fluids throughout the day, not just before you exercise,” says sports nutritionist Nancy Clark, R.D., author of Nancy Clark Sports Nutrition Guidebook
. Then right before you head out, grab a salty snack, like a handful of pretzels. “Sodium holds fluids in the body, which slows the rate of dehydration,” she says.
If your run, walk, or bike ride will take less than an hour, it’s enough to sip water throughout your workout. For sessions that last 90 minutes or more, drink before you feel thirsty—say, four to eight ounces every 15 to 20 minutes. A sports drink can also help keep your carbs (for energy) and your sodium (to retain necessary water) in check.
Try precooling—think hanging out in front on an air conditioner for ten minutes or wearing an ice vest—to lower your core body temperature, which can help increase your endurance in the heat, says Bergeron. Reap a similar effect by taking a cold shower, or even slurping a slushy before your workout: Australian researchers found that drinking the icy beverage an hour before exercise extended runners’ duration.
Use the same trick mid-workout too: A 2011 study found that placing ice on the neck lowered athletes’ perceived thermal strain, meaning they didn’t feel as hot and could exercise longer. Or try this method: Fill a bag with ice and tuck it into your sports bra between your shoulder blades for a few moments.
In sweltering conditions, ignorance may indeed be bliss: In two new studies, cyclists could maintain their intensity or ride longer when they believed the temperature was lower than it actually was. Participants didn’t assume the heat would compromise their ride, so they didn’t feel as if they were working too hard, says Greg Chertok, M.Ed., director of sport psychology at The Physical Medicine & Rehabilitation Center in Englewood, New Jersey.
While it’s smart to check the forecast in the morning so you will know what you’re in for and can take the necessary precautions, obsessing over the heat can work against you. Anxiety can spike your heart rate and lead to rapid breathing and hyperventilation—making any workout feel immediately and immensely more difficult to sustain.
Shield Your Skin
Direct sun exposure on the skin not only increases body temperature but can also limit your body’s self-cooling abilities because sunburn impairs sweat glands, says Bergeron. (The risk for skin cancer is increased too.) Before you head out, cover every inch of your skin with sunscreen or clothing (in a wicking fabric that’s lightweight and light colored).
Early morning is the safest time to exercise outdoors in the heat of summer. Working out after the sun goes down can also reduce your risk (although in some Southern states, evening temps can be just as high as midday ones). These guidelines will help you adjust your workouts based on the conditions, no matter what time you head out the door.
Heat |70-89°F| & Mild Humidity |<60%|
The danger: Hot-weather workouts put extra stress on the body.
Dodge it: Cut down on intensity or duration. Take breaks (walk or sit in the shade) as needed to keep your body temperature and heart rate from skyrocketing.
High Heat |90°F|+ & Humidity |>70%|
The danger: Heat loss through the skin is compromised in really hot weather (heat is absorbed back into the body instead). Plus, sweating alone doesn’t cool the body—sweat evaporation (turning that water into vapor) does. Increased air moisture stifles the process, trapping heat inside the body.
Dodge it: Have a high-intensity workout scheduled? Take it inside or switch to a shorter, less intense workout. Save your tough session for another day.