24 Tips for Exercising in the HeatA Realistic Guide |
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I know what you're thinking: not another one of these. Well this page is different. While there are plenty of articles about exercising in the heat, they are mostly not particularly useful, incomplete, and out of touch with the reality of human nature and complications of life. As of September 2020, this is my 19th summer of living in the Coachella Valley (Palm Springs area), and these tips are based on my personal experiences of exercising in the heat. Some tips are also based on exercise physiology research. I am not a doctor, and this should not be considered medical advice. However, I have more experience exercising in the heat than most doctors and most journalists. So here's how to do it. You can click on each tip below to read more details. |
Tip #1: Don't do it.Seriously. Do you want kidney stones or loss of short-term memory? Think about what your family will go through if you die. Try to go around sunrise, or go up into the mountains, or exercise indoors on a treadmill or exercise bike (with a fan). Exercising in the heat is not a good way to improve fitness or burn fat, and everyone has a physical limit that cannot be overcome by mental determination, even if you're tough as nails and extremely fit. Slogans like "no pain, no gain" and "mind over matter" are just silly words when it comes to extreme heat. While exercising in the heat might build mental determination, there are other ways to do this. Weather-related death statistics in the US:
That said, there are other reasons why people exercise in the heat such as medical issues and time issues with work and family. A person who works swing shifts, doesn't own a car or has a limited budget for gas or gym memberships, has morning digestive issues, has insomnia, or takes meds that increase hours of sleep may end up exercising in the heat because it may be very difficult to exercise another way in the summer. Whatever the reasons are, there are people doing it who can't be persuaded otherwise. It's the reality for some people, so this page has tips on how to actually do it and decrease risk. |
Tip #2: It takes about 2 weeks to acclimatize to exercising in hot weather.This makes a big difference and reduces risk. People who live in the desert gradually do this in late spring and early summer. For someone visiting or just moving to a new area, it's important to start small and slowly build up heat tolerance. |
Tip #3: Know your personal limits for dry heat and humid heat, through recent experience.This varies greatly from person to person, and children generally have more difficulty with heat than adults. I do okay running on flat ground until about 105 °F in dry heat and full sun. For most people this dry limit is a lot lower, even 80 °F for some people. Don't be fooled by hearing about the Badwater Ultra in Death Valley because those runners have access to water during the hottest part of the day, from their support vehicles. That completely changes the nature of the event. To go solo in those temps, they would need to carry a significant amount of ice, like half their body weight or something crazy like that. Accounting for humidity is complicated. Here are 3 ways to do this: wet bulb globe temperature (most advanced), heat index + sunshine, and wet bulb temperature (simplest). Exercise recommendations based on wet bulb globe temperature:
Recommendations from the National Weather Service based on heat index which is for shaded conditions:
Recommendations for children:
The wet bulb temperature is a simple way to compare different levels of humidity and temperature. Unfortunately, this value is not published on weather web sites, but it can be found with online calculators or by waving a wet cloth around and putting a thermometer inside it. It's always somewhere between the dew point and the air temperature. It's a mistake to use dew point alone without also considering temperature. At extremely high temperatures and low humidity, evaporation rate may exceed sweat production rate (translation: your skin may be dry), so unless you're wearing a soaking wet shirt and hat or your body can produce a tremendous amount of sweat, it could be more dangerous than the tables say. |
Tip #4: Some types of exercise are easier than others.The type of activity influences how hot a person will feel and whether the body can regulate temperature properly. Going downhill is cooler than uphill, and traveling on flat ground is between the two. Cycling is cooler than running. Walking/hiking is cooler than running. Even walking can be warmer than working a job outdoors, if the temperature and humidity are the same in both cases and the job is not constantly physical. Some people can work outdoors when it's 120 °F (almost 50 °C), although I have to wonder what kind of health issues that could be causing, such as damage to the kidneys or brain. When it's 120 °F, you won't see somebody running long distance unless they have access to a garden hose or bucket of water. |
Tip #5: It takes time to warm up, about 15 minutes.Just because you can walk across a parking lot when it's 115 °F doesn't necessarily mean you can hike trails when it's 95 °F. Maybe, maybe not. One time I saw people doing very short walks during their lunch break when it was 122 °F (50 °C) officially. There's no way any of them could have done a real hike in that temperature, although probably all of them were locals living in the desert. Appearances can be deceiving. |
Tip #6: Don't push 100% in hot weather. Listen to your body.Just because you can, doesn't mean you should. And even if you do, you'll still be slower than doing the same workout in cooler weather. Exertional heat stroke (EHS) is caused by physical activity and is more likely to lead to kidney failure than classical heat stroke which doesn't involve exercise. It's better to do hard workouts indoors or on cooler days. |
Tip #7: Estimate temperature changes and prepare for them. Plan your exit strategy.Temperature drops 3 to 5 degrees per 1,000 feet of climbing. Temperature also increases by a similar amount per hour in the morning in the desert, so how fast you climb affects the temperature change that you experience if you experience any change at all. On rare occasions it can heat up by 8 to 10 degrees in 1 hour, but I've never seen this rate sustained for more than an hour. If you ever have to decide an exit path, it's better to do this calculation ahead of time instead of deciding whether to climb or descend while you're experiencing dehydration, heat exhaustion, or low blood sugar which is not the best state of mind for making decisions. |
Tip #8: Sunlight makes a big difference.In the early evening, the temperature only drops a little compared to the afternoon, but the drop in sunlight helps to make it easier. In a low desert area in the summer, it is still less risky to exercise in early morning because of the lower air temperature, even if the sun is up. The National Weather Service says that full sunlight is equivalent to adding up to 15 °F to the heat index which is for shaded or evening conditions. |
Tip #9: Wind can help, but sometimes it's bad.Breezes can help with cooling a little. Ridges are generally cooler than canyons for this reason. But if the air temperature is above body temperature, the wind will not be helpful unless your skin is wet. That's because convection will actually drive heat into the body in this case. Only evaporation or ice can cool if the air temperature is above body temperature. This is the reality of thermodynamics. At extremely high temperatures, the wind can be dangerous by driving more heat into the body through convection than what is lost through evaporation. |
Tip #10: Bring more water than you think you'll need.It's easy for even experienced people to underestimate water consumption. The amount of water needed increases significantly with temperature and is best learned through experience of shorter workouts before attempting a longer workout. If you carry too much, it's just extra weight. If you carry too little, it can be deadly. If the humidity is low, some people can be outside in hot weather for a surprising amount of time. All is well until they run out of water. |
Tip #11: Keep all your water in the freezer the night before.
Ice water cools the body when you drink it. If it's not melting in time when you need to drink it, you can accelerate the melting and cool yourself by pressing ice against your body. I've been doing this for years and never got frostbite, although in theory it could happen if you don't move it and blood circulation is low, or if weather is not hot. With frozen water bottles, you can hold them under the arm pits. Water packs/bladders can be removed from insulation and placed against the chest or back. In the photo, I cut a melt-control flap that allows ice to be pressed against the back while inside the pack. An insulated drinking tube helps to keep the ice water cold when drinking. If you don't have an insulated tube, then it's a good idea to blow the water back into the pack and space out drinking longer so that more cold water is entering your mouth. |
Tip #12: Consider wearing an ice vest.I haven't tried a commercial one, but from my experiments with frozen water packs and frozen water bottles I can say that an ice vest would likely provide significant cooling. This requires experience to estimate how long the ice will last, and I'm not aware of a commercial product that allows the user to drink the melted ice. |
Tip #13: To spray or not to spray?Bring a spray bottle or mister, but save it for the end of the workout unless you're absolutely sure you brought plenty of water. You'll go through water faster by spraying it or pouring it on your head, so if you underestimate your water requirement and go through your supply, you'll wish that you had been drinking it instead. That said, the cooling effect of spraying/pouring is greater than just drinking it. With an unlimited water supply, such as running around the block of your neighborhood, spraying or dunking hat/shirt in a bucket of water is clearly the best choice. In most other cases, experience is very important in judging whether to drink or spray/pour. For a longer workout away from water sources, it's usually better to err on the side of drinking it. In high humidity, evaporation is less effective for cooling. |
Tip #14: Bring lots of salt in some form.It's easy to underestimate how much salt you need in the heat. Muscle cramps or dizziness can be signs of low sodium. Some people think it's gross to consume a salty drink, so for business reasons some sports drinks do not have enough salt. Salty foods are another option. The amount needed can vary from person to person, so you might not be able to estimate your own salt needs based on what another person is consuming. Hyponutremia (low sodium) can be deadly and progress quickly compared to other dangerous conditions. Drinking water without enough salt can rapidly lower sodium concentration. If you think you're low on sodium and run out of salt, it's better to pour water on your head instead of drinking it. |
Tip #15: Bring lots of carbohydrates in some form.You'll need more carbos in the heat. Ignore all the low-carb advice out there because that's only related to appetite and weight loss and not beneficial for exercise. You won't find a professional marathon runner on a low carb diet because he or she would not be able to compete with the other runners. Some fast ultra runners may do some training low-carb, but they race with carbohydrates if they want to run fast. I think a moderate-carb diet is also okay for a lot of people and might be healthier for some than high-carb on a regular basis. However, I believe a lot of the low-carb advice is motivated by making money and not in the best interest of the person following it, even if they lose weight. The long-term effectiveness of any diet is related to the Satiety Index. Why don't you hear about this much? Because nobody can make money off that when the scientific answers are given away for free. The Glucose Index rates carbohydrates according to the blood sugar spike they produce. Eating carbohydrates during and after exercise is less likely to spike blood sugar than eating them at other times. Low blood sugar and heat exposure are both contributing factors in kidney failure. |
Tip #16: Avoid caffeine and other drugs.Obviously some drugs are a really bad idea to use in the heat, but caffeine is a sneaky one because it might seem like a good idea, but it causes blood vessels near the skin to constrict which reduces blood flow to the skin. This makes you feel hotter and reduces your body's ability to cool itself. |
Tip #17: Get a very short haircut.Sounds funny but this really makes a difference. Even 1/8" (3mm) hair feels cooler than 1/4" (6mm) hair. |
Tip #18: Ventilate your head.
If you wear a sun hat, it needs to have really good ventilation like a mesh that you can see through. Or you can wear a golf-style visor, or just cut holes in the top of the hat like I did in the photo. Otherwise it's cooler to just not wear a hat. I haven't gotten a sunburned scalp yet, but I may consider sunscreen on top just in case... |
Tip #19: Don't wear a shirt.I've found that even a synthetic white shirt with very thin breathable fabric is a little bit warmer than not wearing a shirt, although I can't speak for people with darker skin because the trade-off might work differently in full sunlight. Wearing no shirt is definitely cooler than wearing a dark cotton shirt. This is obvious when it's really hot. What's not obvious is that when it's "just warm" outside this will reduce your water requirement and make it less likely that you'll run out of water and can increase workout speed slightly. For women, this strategy is more complicated, but the same is generally true: less clothing is cooler than more, and light clothing is cooler than dark. |
Tip #20: Wear shorts instead of pants.This may seem obvious, but if there are bushes with thorns, it's tempting to wear pants for protection. Shorts + gaiters allow some ventilation which is better for conserving water and staying cool. I've seen some people choose to wear pants in warm weather. They usually aren't moving very fast, and it's usually not super hot. |
Tip #21: Carry a mylar emergency blanket or an umbrella.A mylar blanket can be used for shade, but don't wrap it tightly around your body as you would in cold weather. Your body needs airflow for cooling. I've seen Pacific Crest Trail hikers using silver umbrellas as they effortlessly descended into the desert on a hot afternoon. Other hikers were resting in the shade of boulders. They did not look good and were waiting for evening to start hiking again. |
Tip #22: Never sit down or lie down in full sunlight.The ground and rocks are at a much higher temperature than the air. Even the air near the ground is warmer than the air that is 4 to 6 feet off the ground, where official temperature measurements are made. Even if you really feel like sitting down, don't do this if you are experiencing heat exhaustion. Find some kind of shade first. If you do this, it's important to leave some bright piece of clothing out in the sun where searchers can see it. Otherwise they might never find you. This happens every once in awhile in Joshua Tree National Park. People can disappear for years before their remains are eventually found or not found. |
Tip #23: If you're about to die...As a last-ditch hail-mary effort, you can apply ice to the carotid arteries of the neck. This is a temporary and risky method because it cools the blood that enters the brain while it does little to cool the rest of the body. You may be tricked into exerting yourself more than you should, so it's important to slow down or rest with this method, even if you feel like you can go faster. I've done this once when I was getting dizzy right before the crest of a trail. It did work very well, and it wasn't too risky because after I reached the crest it was downhill the rest of the way back to my car. The descent was only 1,000 feet, so there wasn't a significant increase in air temperature compared to the cooler feeling of running downhill. |
Tip #24: Please refer to Tip #1Avoid exercising in the heat as much as possible. Notice that in all the other tips, experience is very important, and there are many subtleties. It's a delicate operation, and a mistake can be fatal. |
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Web site created by Perry Scanlon. |