Training in the Heat: All About Heat Acclimation, Nutrition & Exercise Tips
by, Dr. Josh Axe, Abe Ankers, Tom Koscher, and Tina Sturm-Ornezeder
For most people, the end of winter and the warmer days of spring can feel like a sigh of relief. Instead of dark mornings, cold weather, and icy paths, the sun’s heat brightens our path and improves our mood dramatically.
While warmer weather inspires outdoor workouts, it is important to take the right precautions when running or training in the heat. Sweat safely! Here’s a guide
Frequently asked questions
How does your body react to heat?
Physical activity at temperatures above 85°F/30°C noticeably strains your body and cardiovascular system. The heat also causes core body temperature to rise. The body reacts by producing more sweat, increasing heart rate, and dilating blood vessels.
Here’s what you can do to best support your body when exercising in the heat:
1. Start slowly when training in the heat
Give the body time to adjust to higher temperatures. Avoid intense training sessions during the first few really hot days of summer and begin slowly. Gradually increase your workout intensity and let your body acclimate.
Listen to your body:
Be flexible with your running schedule and allow yourself the chance to adapt your speed and distance to the conditions. Give yourself a realistic timeframe and run according to how you feel. Mix up your pace and adjust your performance level to the heat.
2. Heat affects your heart
The heart rate is elevated during warmer weather. When running with a heart rate monitor, remember that higher temperatures also boost your heart rate even if you run at your usual pace. Therefore, it might be a good idea to take it a bit slower. The fitter you are, the better your body will cope with the heat, preventing your heart rate from skyrocketing.
Find out your ideal and maximum heart rate with this calculator:
3. Avoid midday heat
Choosing the right time of day for your training runs or races is vital during the summer months. Avoid running in the midday heat; head out in the morning or evening instead. Those times of day are not only cooler but there’s also less ozone in the atmosphere. High ozone values can irritate eyes and airways.
4. Select the right routes
With the sun burning in the sky, adjusting your route definitely makes sense. Asphalt and cement absorb and transfer heart. Hotter days offer a good opportunity to abandon usual road routes and hit the trails. A run or workout in the woods is a lot of fun, adds variety to training, and offers shade. Runners are slower on rough trail terrain, which gives the heart a break. If it’s still too hot (or there’s no forest nearby), you can keep fit and safe by running on a treadmill.
5. Choose the right outfit
The appropriate workout clothes can protect your skin from UV rays even better than some sunscreens. Go for a loose fit and moisture-wicking materials for both your shirt and shorts to prevent heat from building up under your clothes. Wearing cotton clothing while Running in summer is counterproductive: cotton absorbs your sweat without wicking it away and doesn’t dry quickly. Make sure you choose light colors. They reflect sunlight and do not store the heat. Running accessories matter in summertime as much as wintertime. A cap or light scarf can protect the head and shade the face. Last but not least, wear sunglasses with UV protection.
6. Protect your skin
Cover all skin that is exposed to the sun with waterproof sunscreen (sweat is 99% water, after all). The sun protection factor (SPF) tells you how long the sunscreen extends your skin’s own natural protection time. So, SPF 30 means that your skin will be protected 30 times longer than without sunscreen. The higher the SPF, the longer you’ll be protected– if the sunscreen does not slide off in sweat, water, or wear. How much sunscreen you need depends on your skin type, the time of day, and current UV levels. Your level of intense activity and time doing that activity should also be taken into account. Don’t forget to rub some on your neck, the back of your knees, and your ears! Re-apply regularly for the strongest coverage.
Good to know:
The purpose of sweat is to cool your body. When sweat evaporates, it cools your blood vessels and your skin. Greasy sunscreen clogs your pores and make it harder for your body to sweat.
7. Stay hydrated
When running in the heat, your body tries to lower your core body temperature by sweating more. This causes you to lose fluids and minerals like magnesium and iron. Even a small change in your fluid balance can lead to major performance losses. The most important thing is to start off well hydrated. Drink regularly throughout the day and stick to diluted fruit juices, teas, and water (tap or mineral). If you’re going to be working out for more than an hour, make sure to have a water bottle with you and take a sip from time to time. Many cities also have public water fountains. If you don’t want to carry a water bottle with you, plan your runs on routes where water is available. Find out how much water you should drink a day:
Find out how much water you should drink a day with this calculator:
8. Eat adequate vitamins and minerals
Wholesome foods rich in vitamins and minerals should be a regular part of a healthy meal plan year-round. But when it’s hot outside, your body loses more minerals than usual due to sweating. Since the body can’t produce minerals and enough vitamins, they have to be obtained through food. Eat foods like bananas, dried apricots and whole grains before a workout to elevate mineral levels. Protein bars with added vitamins and minerals make nutrient-rich post-workout snacks.
9. Don’t be too ambitious
If you experience headaches, intense thirst, muscle cramps or dizziness, you should stop immediately, look for shade, and drink some water. Excessive confidence is often your worst enemy when running in the heat, so leave it at home. Your body also needs longer to recover when it is very hot. If you don’t feel well when the heat is bearing down with high humidity, then it’s probably a good idea to take a rest day or opt for a more refreshing training alternative like swimming.
10. Find great training alternatives
Pounding out kilometer after kilometer while drenched in sweat with a bright red face is not everyone’s idea of a fulfilling workout. It doesn’t have to be like that. When the pavement is scorching, trade your running shoes for a pair of wheels. Biking is a good way to cross-train and enjoy the cool breeze. Water aerobics or aqua jogging are also cooling ways to work the same muscles as dryland running.
What Is Heat Acclimation?
This technique for improving performance in the heat might just be the stuff of miracles. Cue the — quite frankly — revolutionary concept of hot water immersion.
…is the process of adaptation that occurs with repeated heat exposure. The theory is that once you’ve acclimatized to running in the heat, then both your hot-weather and cold-weather runs will get faster.(1),(2) Various methods have been tried and tested with some success(3) but for those of us not in lab coats, the idea of running to exhaustion in tropical heat with a rectal thermometer inserted is neither attractive nor realistic.
That’s where the experts at Bangor University in Wales come in: They have developed an ultra-simple, user-friendly way of adapting to the heat which you can do at home and can improve cardio performance such as running.(4)
Sounds too good to be true? It gets better. This technique costs next to nothing and is explained right in the following sections. First though, let’s look at what happens when we exercise in the heat.
Feeling the Heat
If you’ve ever felt the strain of intense heat or exercise, imagine what happens when the two are combined. Exercise in the heat is a double dose of stress. The muscles and skin compete for blood flow in an attempt to maintain oxygen supply and lose heat. It’s a classic catch-22 that leaves runners dehydrated and breathing hard even while exercising at lower intensities.
When our central nervous system…
…senses an increase in temperature, around 3 million sweat glands enable water to be released at the skin. This amazing heat loss mechanism keeps our bodies from overheating, but it also means we lose fluid. More than half of our blood is water, and this water is literally sweated out. In hot conditions, sweat rates of 1L per hour are common (3.7L per hour being the highest recorded(5), resulting in rapid fluid loss.
Ever felt a breathless, heart-thumping sensation when running in hot weather?
The net effect of this dehydration and increased blood flow toward the skin provides the muscles with less blood. The heart pumps extra hard in effort to make up the deficit.
Not surprisingly, all of this extra strain impacts performance.
…have shown that time to exhaustion in hot (>30°C) conditions is reduced by a whopping ~45% compared to lower temperatures.(6)
If your training performance has ever suffered in summer, then it’s time to consider heat acclimation. The good news: it’s easier than you may think.
Heat Acclimation by Hot Water Immersion
The hot water immersion (HWI) method of heat acclimation is quickly gaining popularity, challenging the traditional ice bath as the post-exercise treatment of choice.
Only attempt this heat acclimation strategy if you are healthy and do not have a heart condition. Ask your doctor if you are unsure. The beneficial effects of heat acclimation remain for up to two weeks,(7) so if you’re preparing for a specific event in the heat, schedule your heat acclimation strategy in the 14 days prior.
The real beauty of the HWI method is its simplicity. Go for a run, soak in a hot bath, repeat each day. In a recent study,(8) Mike Zurawlew and Neil Walsh demonstrated the effectiveness of post-run hot baths in promoting heat acclimation and enhancing performance. In this study, 5K run time in the heat (30°C) was improved by 4.9% after hot water immersion.
The Hot Water Immersion Method: How it Works
- Exercise at moderate intensity for ~40 min in temperate conditions; “you should feel warm, but comfortable.”
- Immediately take a bath at 40°C (104°F) for 40 min, immersed up to the neck.
- Increase bathing time by 5 min each day for a total of 6 days.
CAUTION! If you feel too hot, get out and cool down. Sit for a few minutes to recover.
Zurawlew and Walsh went one step further last year, showing that HWI can induce heat acclimation and improve performance in both highly trained and recreational individuals.(9) This is huge. It means whether you are an experienced marathoner or approaching your first 5K, HWI can work for you.
In both studies, six hot baths were enough to increase thermal comfort, lower core temperature, and quicken the onset of sweating. Other key hallmarks of heat acclimation include reductions in sweat electrolyte concentration and heart rate, and increases in total body water levels, blood plasma volume, and skin blood flow — all of which benefit your performance in the heat.(10)
Based on the findings of this landmark study, Professor Walsh, Director of the Extremes Research group at Bangor University, has developed a practical strategy for heat acclimation. This HWI method requires only 6 days to achieve significant results, with heat exposure gradually increased from 15 minutes on the first day to 40 minutes on the sixth day.
Altitude acclimatization is known by the phrase “live-high, train-low.” According to Professor Walsh, “the new mantra should be ‘Train-Cool, Bathe-Hot’.
So there it is; your weapon against the heat. Run, Soak, Repeat!
There is a lot of speculation about the positive effect of exercising in the heat. First the good news: yes, you burn more calories when you’re exercising in the heat. (Note: bodies also burn more calories when shivering from the cold. But few of us are likely to exercise in such cold conditions – and, it’s dangerous!)
Here are the facts that runners need to know about metabolism during hot workouts.
Fact 1: “The higher the body temperature, the more calories burned”
As the outdoor temperature rises, so does your body temperature. Your system then has to work harder to keep the body at a normal temperature. More strain is put on your lungs and heart as a result of the hot conditions, and since the body has to work harder, it burns more calories.(1)
Fact 2: “Changes in temperature affect calorie burn”
When you work out in the heat, your body tries to maintain an average temperature of 36°C.(2) With every variation in temperature, you burn more calories to compensate for the fluctuations. This energy is drawn from excess calories and fat reserves.
Fact 3: ”Your body sweats to cool off”
Your body’s natural cooling system kicks in when you work out at higher temperatures. You start producing more sweat to release the heat and reduce your body temperature. The sweat on your skin evaporates, which keeps your body temperature within a healthy range.
…increased sweat production does not necessarily mean higher calorie burn. If you don’t sweat very much, you still burn as many calories as your heavily sweating workout partner.
Most people don’t like to sweat, but without the body’s natural temperature regulation, our performance would drop even more. If you start sweating right at the beginning of your workout, it doesn’t always mean that you are out of shape. Your body has learned to start cooling down early. That’s why well-trained athletes start sweating faster than others.
Fact 4: ”Your basal metabolic rate influences your calorie burn”
You burn more energy through the combination of heat and exercise. That is the good news. But this is not just because of the temperature — your basal metabolic rate also plays a role here. This depends on factors like age, weight, and height and varies from person to person.
Good to know:
Did you know that the higher a person’s basal metabolic rate, the more calories they will burn?
Calculate your basal metabolic rate:
You can change your BMR by building muscle mass. A more muscular frame has a higher metabolism; muscles burn calories faster than any other bodily function. Functional bodyweight training is a great way to build muscle mass.
Most people naturally burn more calories in summertime because they’re more likely to partake in organic outdoor exercise.
Fact 5: “Exercising in the heat has risks”
Working out in the heat might get you a nice tan, but it also has some risks. Heat and humidity can make the body feel exhausted quickly.
Stop working out the moment you experience any dizziness, slowed reflexes and responses, or nausea. Look for a shady spot to rest and drink some water. Give your body time to adjust to training in the heat.
High temperatures mean that eating certain foods before and after runs can help you perform your best as the temperature starts to soar.
Summer Workout: Best 6 Drinks & Foods for Runners in the Summer
1. Coconut water
Known as nature’s sports drink, coconut water is ideal for rehydrating after summertime runs instead of artificially sweetened sports drinks or plain H2O. Read the nutrition facts carefully, though: many coconut waters are packed with added sugars.
Coconut water is loaded with potassium. Potassium is one of six key electrolytes (the nutrients that are critical to preventing dehydration). Potassium also helps to keep blood sugar levels stable and assists with muscle function and relaxation. If you’re counting macros, note that coconut water is lower in carbohydrates than normal sports drinks.
Avocados are incredibly nutrient-rich and full of vitamins and minerals, including vitamin B and vitamin C, which aren’t stored in the body and need to be replenished daily.
For runners, avocados are especially helpful: they’re full of heart-healthy monounsaturated fats which reduce cholesterol and lower blood pressure.(1) They are full of soluble fiber which helps keep you feeling full for longer — perfect for long run mornings.
Avocados have one more surprise benefit: they are actually one of the top plant-based protein foods! Regularly eating avocados in a balanced diet can contribute to the development of lean muscle mass. Try adding smashed avocado, herbs, and salt to a piece of whole-grain toast before heading out on a run.
These little nutrient-dense fruits are fantastic for runners. Blueberries have a high water content, so consuming them before working out in the heat will help you stay hydrated during extra steamy runs. They’re also high in antioxidants, protecting against numerous chronic diseases like heart disease.
In fact, one study found that when runners ate blueberries before a 5-kilometer run, their post-run “good” cholesterol levels increased while insulin levels decreased.(2) Luckily, blueberries are plentiful during the summer. Have a handful before heading out for a run, or try a smoothie with blueberries, Greek yogurt, and kale.
Did you know that kefir, a cultured dairy product, is one of the best sources of probiotics? Probiotics are beneficial gut bacteria that boost the immune system, help you maintain a healthy weight, and prevent the development of leaky gut syndrome. These are helpful benefits for any athletes, but when it comes to runners, kefir is great because of its ability to help improve allergies.
If you suffer from hay fever or other seasonal allergies, you might find that spending time running outside exacerbates your condition. Regularly consuming kefir, however, can help alleviate that, as the microorganisms found in kefir help the immune system naturally suppress allergic reactions.(3)
This seed’s popularity has skyrocketed in recent years and with good reason. It’s a complete protein source, meaning it provides all 20 amino acids the body needs, including the ten essential acids that our body doesn’t produce on its own. If you don’t eat meat or just want an extra protein boost, serving quinoa as a side dish or building a meal around it can help you boost your protein intake.
Quinoa is great in summertime because quinoa is also a complex carbohydrate, helping to sustain you during challenging runs while aiding in weight loss. Gluten free runners rejoice: Quinoa is a safe food for you! Enjoy it as an alternative to pasta the night before a big race or a longer run!
Spinach should also be on your shopping list when exercising in summer. Running or training in the heat can take a toll on your body. Luckily, this leafy green can help you reach peak performance.
One study discovered that nitrates, which are found in greens like spinach, can improve performance during short bouts of exercise, like sprints or interval running. In fact, after just five weeks of training, athletes given a nitrate supplement of 400 milligrams — the equivalent of about 2-3 cups of fresh spinach — improved their muscle fiber composition.(4) Improvements in muscle fiber allow athletes to train harder and boost performance. Enjoy spinach in a chia-seed smoothie before running or afterward in a Grecian spinach salad.
Choosing the right foods in the summer can make it easier to work out in the heat, both before and after your run. Integrate these nutrition tips into your summer diet to improve your running performance. Your body will thank you!
Are you ready to kick off your summer running? Download the adidas Running app and clock all your sessions to keep track of your training progress.