You Can Get Used to Working Out in the Heat
Nobody likes to feel sluggish and sweaty, so when the sun sets to get hot, I understand that you prefer to work out in an air-conditioned gym. But the human body can actually adapt to exercise in the heat! In a few weeks, these temperatures will become your new normal—and research shows you may enjoy a slight boost in productivity when the weather cools down again.
Hot workouts can be dangerous, so I hope you have some common sense about running in the heat. Among the most important: drink to stay thirsty (or a little more), stop and get help if you start to feel symptoms of heat illness, such as nausea, dizziness or weakness. And while working on your ability to run in the heat is great, don’t do anything stupid—stay home if the temperature is hotter than you can handle , and keep an eye on smog and ozone levels (which get worse on hot days). ) if you live in an urban area.
Why does working out in the heat seem so unpleasant?
Running is poor and the heat is poor, so running in the heat is poor. But that’s not all: working out in the heat feels even worse than you’d expect when you add those two factors together.
When it’s hot, your brain processes effort differently, so even before you overheat, you feel sluggish. In a study published in the European Journal of Physiology , cyclists who trained in a laboratory at 95 degrees were slower than when they performed the same time trial at 59 degrees. This makes sense, but here’s the weird part: they didn’t overheat and then slow down. They were slower from the start . It seems that on hot days our brains actively slow down our bodies to conserve energy.
As we continue to exercise, our bodies heat up. In another study published in the Journal of Applied Physiology , when participants were asked to cycle to the point of exhaustion, they defecated when their core temperature reached 104 degrees, regardless of what temperature they started at. The athletes who took longer to reach this temperature were those who wore fancy water-cooled jackets. You can imitate this effect in your workouts by drinking ice-cold drinks and dousing your head with water . The longer you can keep your body cool, the longer you will be able to withstand heavy efforts.
It’s heat and humidity
But cooling the body is not a complete solution. Pouring a cup of ice water over the head or injecting it into the abdomen provides only short-term relief, and water-cooled jackets are impractical outside of physiology laboratories. So let’s see what happens in the real world.
Your body tries to cool itself, in part by sweating. When moisture evaporates from your skin, it takes some body heat with it. However, in humid weather, sweat does not evaporate as easily because the air is already full of water vapor. So when we talk about “warmth,” we actually mean something like “sensed heat,” which is a combination of heat and moisture. This heat index chart shows the relationship:
In the heat (and humidity) you will run slower. While you can find charts like this that predict how much slower you’ll run over a distance, the truth is that the effect the heat will have on your running depends on whether you’re used to the heat, as well as your body size.
That’s right – not your fitness level, but your actual physical size. Larger people have more muscle, fat, or both. Muscle generates heat and fat acts as an insulator. On the other hand, smaller people generate less heat, but they have more skin through which that heat is dissipated—the old surface area to volume ratio . This is why petite runners perform better in races on hot days.
Some people think that being more fit allows you to handle the heat better, but this is only partly true: the fitter you are, the more heat you produce, simply because you’re so good at working hard. Short of changing your body shape (which is possible, but hardly a short-term solution), what can you do to better handle training in the heat? The answer is simple: spend more time exercising in hot weather.
Why You Should Start a Thermal Adaptation Protocol
Running in the heat makes you a better runner in the heat—and it makes you a better person, period.
Let’s say you do all your workouts outdoors this summer, while your equally fit twin does the same workout on a treadmill in an air-conditioned gym. Who do you think will finish first in a 5K race on a hot August weekend? That’s right, you will do it.
But even if the weather is unseasonably cool that August day, your heat training will still help you beat your twin. Part of the magic of heat training is that it increases the amount of blood in the veins (routinely directing it to the skin for cooling, but still having enough blood to feed the muscles). The effect has been compared to a mild, completely legal version of blood doping. Scientists are still debating exactly how this effect works and whether it always happens when people try to adapt to heat, but overall the evidence is pretty strong and I think we should all try to get some of these adaptations if we we can do it safely. .
Here’s the bad news: Adapting to the heat takes work. It is not enough to sit under the air conditioner all summer and go outside only occasionally to exercise. A study published in the European Journal of Applied Physiology found that people who did not exert much effort to exercise in the heat did not have better heat tolerance in the fall than in the spring. If you want the benefits of heat training, you’ll have to work for them.
How to adapt to training in the heat
Option 1: Train as usual, but without avoiding the heat, for two weeks.
In scientific studies, heat acclimatization protocols for athletes typically involve 7–10 days of consecutive heat training for 60–90 minutes each day. A simpler method that can be done by entire teams or individuals is to simply do normal training in the heat for about two weeks.
Calm down first. Remember that your body is still trying to convince you that you are very tired and need to slow down. Safety guidelines for workers provide a reality check. On the first day of a heat wave, the Occupational Safety and Health Administration (OSHA) recommends giving workers only 20% of their normal workload. They should slowly increase to 100% over the course of a week.
Option 2: Spend two hours in the heat every day, whether you’re exercising or not.
This US Army training protocol is a good outline for heat adaptation: it says spend at least two hours in the heat every day and include cardiovascular exercise (such as running, biking, or something increases heart rate). as part of it. If you can’t make it two hours without experiencing symptoms like nausea or dizziness, do your best and consider the two-hour target as a goal to work towards.
You can expect better heat adaptation after about two weeks of spending two hours a day in the heat, although you may start to see results in just a few days.
Option 3: Visit the sauna after every workout.
A way to combine the above protocols without relying on the weather is to step into a sauna or hot tub after your workout. If your gym has a sauna, this is a great way to take advantage of it. Going to the sauna after your workout will help you acclimate to the heat, and you can do this even if your workout was not very hot. The time spent in the sauna can range from 15 to 30 minutes, ranging from shorter to longer.
How to Maintain Thermal Adaptation Even in Cool Weather
To remain adapted to the heat, you will have to continue to spend time in it. You can take a few days off, but if you take a week off, you’ll start to lose your hot weather super powers. This adds up quickly: the Army estimates that after three weeks you will have lost about 75% of your adaptations.
To continue your workout in cooler weather, you can try wearing long sleeves and tights, as elite runner Kara Goucher did while training for the world title race in sweltering Osaka. (She won the bronze medal, becoming the first American woman to do so.) She also spent several weeks in Osaka before the race began; Traveling to experience the heat may be an option worth considering if you’re an avid athlete with time to spare.
You can also try the opposite of this advice to keep cool and choose to run during the hottest part of the day on paved roads without shade. Or return to the sauna after your cool-weather workouts. Whatever you do, stay safe and enjoy your new superpowers.