With training, our bodies can adapt to hotter and hotter conditions — but there’s a limit.
This summer’s Olympic Games could be the warmest in decades. Tokyo, where the Games will be held, may see dangerously high temperatures, in excess of 90 degrees.
The athletes will likely be prepared. Scientists like Oliver Gibson, an exercise physiologist at Brunel University in the UK, have spent decades studying how athletes can adapt to extreme heat conditions. He says that with training, the human body has a remarkable capacity for cooling itself when the temperature rises.
These days, though, Gibson is less worried about the athletes. While running a marathon in 90-degree heat can be dangerous, even with preparation, there’s a much larger threat for everyday people coping with the new realities of climate change. “A lot of what we’re doing now is taking the decades’ worth of insight that we’ve gathered from the athletes and starting to apply it to the general population,” Gibson says.
Coping with heat stress is a growing issue that “will affect more than just your dozen or so Olympic finalists,” he says. “Millions, billions of people are undoubtedly going to be affected by climate change.” Heat emergencies are already the deadliest weather events, and are likely to keep getting worse. To beat the heat, we’ll need to confront it, Gibson says. He believes that research into elite athletes could help make our bodies more resilient in a warming world.
This conversation has been edited for length and clarity.
Brian Resnick
Can anyone adapt to the heat, or is this just top athletes?
Oliver Gibson
Yes, anybody can adapt to heat. We’ve recently published work on elderly UK residents who had very little heat exposure. We asked them to do exercise on the treadmill for a short period of time. And then [they sat] in a warm bath, to keep their body temperature high. What we’ve shown is, within five days, they can adapt to the heat [under the supervision of medical professionals].
Brian Resnick
When you say “adapt to the heat,” what do you mean?
Oliver Gibson
What we look to do with heat adaptation is improve the baseline of the body. If an athlete trains in the heat for two weeks, we know that their core body temperature will be reduced by perhaps about 0.5 degrees Celsius, as an average. Some a little more, some a little less.
What that’s doing is dropping the existing body temperature so that when they invariably heat up, they’ve got a bigger window. They can exercise for however much longer it takes for them to increase by that amount.
And then, a body will start to sweat sooner. Only a small change in temperature will start the sweating. And the signal to sweat will also come with a greater magnitude. So it won’t be to sweat minimally later; it will be to sweat maximally sooner. The rates of dehydration will be higher and quicker.
Brian Resnick
Are athletes better at adapting to the heat?
Oliver Gibson
Athletes have earned their advantage by years and decades’ worth of training. They have more blood, so they can pump that blood around the body more effectively. So they’re not limited in that regard; they have a larger heart that will generally beat more frequently, so that their cardiac output can respond to the heat.
For the general public, it takes perhaps three or four exposures to the heat to even really start to see the signs that they’re adapting. Whereas an athlete who exercises regularly, the adaptation is right there.
People with prior exposure to heat stress are able to more rapidly induce the same amount of adaptation. So if they already resided in a warm environment, they’ll adapt a little bit more quickly.
Brian Resnick
I’m curious to learn some of the basics here. How does the human body usually cope with heat?
Oliver Gibson
The human body is really effective at dissipating heat. We are the very best mammals — the best beings — for sweating on the planet. So if someone’s exercising in very cool conditions, or even temperate conditions, they can sweat sufficiently to lose any heat. As long as they’re not exposed for too long or become very dehydrated.
Brian Resnick
What happens if they are exposed for too long?
Oliver Gibson
Once body temperature starts to increase, what we then see is a greater distribution of blood to the skin. Blood vessels open up. When someone’s getting warm, you see that red flushing of the skin.
And as a sweat droplet evaporates off the skin, the space underneath, the blood, is then cooled. Cooler blood circulates and cools down in the body.
Brian Resnick
But that system sometimes fails.
Oliver Gibson
We don’t have this infinite capacity to increase our cardiac output or the amount of blood pumped by the heart. We get to a point where there’s just an insufficient cardiovascular response to cool us down optimally. And it’s at that point where the body temperature is going to start to rise.
For lots of people, the challenge comes when both exercise and heat combine. The challenge of exercise is you’ve got competing demands for that blood supply: from the skin from cooling down, but also from the muscles for that activity in the movement.
It gets worse when the environment is warm and humid, such that when the sweat leaves the body, it’s leaving at a slower rate, so there’s not as much cooling. If the area is 100 percent saturated, if the humidity is very high, then all that sweat drips on the floor and doesn’t provide that evaporative cooling.
Brian Resnick
What’s the worst case?
Oliver Gibson
A clinical diagnosis of hyperthermia comes from high body temperature and neurological dysfunction — effectively, the brain becoming too warm. We have this region of the brain, the hypothalamus, which is our thermostat. And the high temperature can actually disrupt that processing system, so actually our bodies would go in reverse and we would actually stop sweating. The signal is confused by extreme heat. That is a near-fatal condition.
Brian Resnick
Something I’m hearing here is maybe: Good cardiovascular health will be important for people adapting to a warming world, to deal with worse heat waves.
Oliver Gibson
Absolutely. Someone — particularly in a mid- to late stage of life — who has a more robust cardiovascular system will have a generally more robust body, whether that’s to the challenge of temperature or any other thing that’s thrown at it.
Brian Resnick
Often during a heat emergency, the public health message is that we need to stay inside as much as possible. And I imagine that’s helpful because a lot of people aren’t adapted to the heat.
But seeing how heat waves are becoming more common, might we benefit from confronting it a bit more, trying to adapt?
Oliver Gibson
I think my philosophy is that the body can respond to heat stress. So as long as we embrace it in a measured way and we’re clever with how we approach the heat, we shouldn’t be in a situation to just avoid. To embrace the stress is absolutely the right approach.
Brian Resnick
Could it be dangerous to try to get adapted to the heat? There’s a bit of a conundrum here: To get better at dealing with heat, we need to train in the heat, but the heat is dangerous if we’re not trained.
Oliver Gibson
If you are looking to adapt to the heat, it’s important to listen to your body, to do things progressively and slowly. We would never say that you shouldn’t try and adapt to the heat. But to go out and be a bit gung-ho or blasé about it, I think, would put you at great risk. So what we always suggest is to do things in a measured way. If you aren’t exercising already, regularly, probably that’s the very first step before you start adding heat into the mix.
But if someone’s used to exercising — even if that’s brisk walking — doing that in a warmer environment shouldn’t come with any great risk, as long as you listen to your body. And the moment you start to feel like you’re overheating — if you feel any lightheadedness, if you start to feel unwell in any regard — then dial it back immediately, seek shade, make sure you’re hydrated.
We’d be comfortable with saying for recreational athletes, perhaps go for the same duration of running in the heat, but dial back the intensity a little bit. Recalibrate your expectations, until you start to see the adaptations. So once you start to see that you’re sweating more — and if you’re measuring your heart rate, when that’s looking like it might look in the cooler conditions — that’s a good cue that your body started to respond. You can push a little bit harder.
Brian Resnick
Do you have any general tips for helping people cope with the heat, perhaps when they’re less than well adapted to it?
Oliver Gibson
Drink frequently. Have a planned drinking strategy and a cool drink with you. Then the other thing is to make the skin cool. To do that, of course, you can seek shade and air conditioning. Even if that’s not available, don’t be afraid to rub exposed parts of the body — the arms, legs, face — with very cold water. That’s something incredibly simple.
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