Heat Acclimatization Tips: How to Prepare for Warm Weather Races and Outdoor Workouts


Heat acclimatization can seem a bit complex, but it’s really just the process in which your body adapts to the stress of heat. With the right training and exposure, the strain of high temperatures and humidity (that can send your heart rate through the roof and make your workout feel way harder) lessens. 

Properly acclimating to warm temps can be the difference between performing at your best and blasting past the competition in an endurance race and your mind and body shutting down mid-race. Take, for example, the Olympic trials that took place in downtown Los Angeles just a few weeks ago. Shalane Flanagan, though she landed a third-place finish, was incoherent as she fell to the ground with symptoms of heat exhaustion after she crossed the finish line. 

“The athletes were struggling because they weren’t properly prepared,” says Douglas Casa, Ph.D., ATC, CEO of the Korey Stringer Institute and Blueprint for Athletes Medical and Scientific Advisory Board member. “Race temps are usually mid 60s, but it was in the 70s at the start of the trials and rising into the 80s in the middle of the race; plus, nearly every athlete was coming from cool climates like Boulder, CO,” he adds.

Even if you’re not an Olympian or a professional athlete, it’s still smart to acclimate your body before diving in to training in the heat—Whether you’ve signed up for The Bermuda Triple Challenge in March, want to run an IRONMAN in a warm-weather climate like Puerto Rico, Mexico, or California, or just want to take your workouts outside after being holed up in the gym all winter. Sure 70 to 80 degree weather is a dream if you’re paddle boarding or walking along the beach, but training? That’s a different story.

For hot weather races, conditioning your body to the heat can mean a 5 percent difference in performance, and anywhere from a 2-3 percent difference in performance in warm weather climates. That’s significant if you’re running even a medium-distance race like a 10-K (If you typically run 6.2 miles in 60 minutes, for example, you could theoretically shave off 3 minutes by acclimating your body.)

“You can look at heat acclimatization as a natural blood doping,” Casa says. “You get an expansion of your plasma volume—about 3-4 percent—when you heat acclimatize so you have more blood that can be shared amongst your heart to maintain your power output, take away toxic waste, deliver oxygen to your muscles, and cool your body down,” he adds.  

So, ready to start training right?

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1. Still Train Outdoors (When You Can)

The nastiest winter weather—rain, sleet, and snow—may be behind us, but if you braved it, kudos. Though the freezing temps won’t do much for your training, it’s the changing landscape of running outdoors you’re after. “In general, you’re going to have better quality training outside than if you’re going to be on a treadmill,” Casa says. You need the challenge of uneven terrain, hills, and the strengthening of your small and large muscles that come with it. “Sometimes it’s just not feasible to safely train or bike outside when you have ice and snow,” Casa adds. That’s when you bring the workout indoors and employ the following heat acclimatization tips! Now that spring is in the air, there are fewer excuses to sleep in or hit the treadmill. 

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2. Work Out in the Heat

First, a disclaimer: Just be sure to talk to your doctor first if you have any concerns. You want to acclimate to heat, not induce heat stroke, the symptoms of which include a body temperature of 104 degrees Fahrenheit or higher, nausea, flushed skin, rapid breathing, and altered mental state. Stop immediately if you experience any of these symptoms and always buddy up for safety.

Consider taking Bikram yoga classes to ease your body into the stress of heat, Casa says; though he adds that it’s more effective to do your normal activity or the one you’re training for (running, cycling, whatever) in heat. To get that effect, Casa has high-level athletes create a heat chamber in their home. “[They] utilize a small, enclosed space like a laundry room or walk-in closet, get two or three space heaters, and put their exercise bike or treadmill in the middle,” Casa says. This technique is really only necessary for athletes who have to leave moderate temperature climates to compete in warm or even hot destination races. So, this isn’t necessarily a “try this at home” kind of tip (and could get you in trouble with your woman if you take over her laundry room or closet.) 

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3. Jump in a Hot Tub or Sauna

“You can get partial heat acclimatization benefits by going in hot tubs or saunas and getting your body temperature up,” Casa says. If you have a hot tub to utilize, make a point to schedule in about 5-6 sessions, soaking in 104 degree Fahrenheit water for 30-40 minutes, the week before the event. If you’re gym has a sauna, sweat it out for 20 minutes 5-6 times the week before an event (the temperature will probably be fixed). Just prepping for spring and summer outdoor workouts? The same prescription applies. Pencil in 5-6 sessions within 10 days of each other to get the acclimatization effect. “It’s certainly a good move to make in May to get ready for the heat of training in the summer,” Casa adds. If you do try it, heed the tips in slide two about staying safe!

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4. Wear Extra Clothing

“The key with heat acclimatization is you’ve got to get your body temperature over 102 degrees, and you have to do this 6-8 times over the span of 10-12 days before a race to get yourself fully adjusted,” Casa says. One way to do this is to wear extra clothing during your cooler workouts to simulate the effect of the heat. Add on extra layers like compression wear and sweats on your run or during your workout to prep your body for those higher temperatures. “Just know it’s more successful if you’re indoors in a fitness center that’s already, say, 70 degrees,” Casa says, rather than outside if it’s still 40 degrees. And, of course, remember the aforementioned heat exhaustion warning signs and always listen to your body.

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5. Mentally Prepare for the Shift

Running in a tropical climate may seem like a coconut-scented, sunshine-drenched breeze, but it can be really grueling. “It’s very stressful and it gets exhausting so much faster when you’re not used to hot temperatures,” Casa says. If you’re thrust into high heat and humidity with no sort of conditioning, you won’t be able to maintain the same pace you normally do. That’s practically guaranteed. And it’s incredibly difficult to push past mental barriers when the physical ones are already taxing.

“Luckily, the mental process becomes a lot easier when you’ve done a lot of the hot workouts beforehand,” he adds. Once you heat acclimatize, you take away the stress of dealing with heat. Even if you’re competing in a much warmer climate, your body temperature is where it normally is, so you can focus on getting your headspace where it needs to be.

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6. Transition into Warm-Weather Workouts

As the heat creeps up on us, start slow and build up the number of outdoor workouts you complete. Try to get your hardest workouts in during the early morning hours or afternoon when the heat breaks. Don’t go out full-force either. Alternate between working out in the gym and working out outside for the first few weeks. Then you can plan some intense workouts in the heat; the goal here is not overloading your system all at once. 

“A world class national soccer team I worked with in the past, before the World Cup in southeast Asia, made the mistake of doing all their workouts three weeks before the World Cup in the heat,” Casa recalls. “They were completely exhausted…trying to do super hard workouts with the new stress of heat. They didn’t account for that being a factor that could tear their players down.” 

If you’re competing in a major endurance event like a triathlon or ultramarathon, you’ve got to be strategic about when you do your workouts, especially once you get to the destination. Complete your most difficult, high-quality workouts in the morning when it’s still cool out (70 degrees Fahrenheit) and plan your medium conditioning work when it’s hot (up to 90 degrees Fahrenheit). Another tip to take away from the heat-exhausted soccer players: Don’t work out every day initially. If you get to your warm-weather destination in advance, scale down your workouts so you have two days on, one day off. 


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7. Hydrate Before, During, and After

Weigh yourself before and after your workouts to get a sense of how much water you’re losing. It’s important to figure out what your fluid needs are in a simulated situation and get yourself used to drinking while working out,” Casa says. Not sure how much water you should be drinking before and after a workout? Check out The 6 Most Basic Hydration Rules Every Athlete Should Know.

While it’s important to drink more, keep in mind that this is a huge stress to your gastrointestinal system. If you’ve spent months, even years, training without hydrating during your workouts, then you might experience nausea, vomiting, and diarrhea when you get into a hot climate.

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8. Travel to Your Destination in Advance

“If you can get to a destination four days before and get in two to three workouts, especially if you’ve done some of the aforementioned acclimatization beforehand, you’ll get some great benefits,” Casa says. Just don’t do any full-out effort workouts. Three days prior to an event is too close to fit in any more heat acclimatization work. Ideally, and if you were a pro, you’d get to the race destination three weeks prior to the event. Most of us don’t have the luxury of taking that much time off. But if you do have some vacation time allocated for this very reason, all the more power to you! Elite athletes go to Kona, Hawaii three weeks before the marathon because it takes about two weeks to get 98 or 99 percent of heat acclimatization benefits, Casa says. Use the first two weeks to get good quality workouts in and elevate your body temperature; the third week should serve as a taper so you’re not doing too many hard workouts that are getting you hot and bothered (in the training sense). 

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