Most people think of summer heat as the enemy of a good workout. But Bill Gifford thinks we’ve got it all backwards.
Gifford spent years researching the science of heat and the human body for his new book, Hotwired. He explained the benefits of heat acclimation training on a recent episode of the mindbodygreen podcast, and what he says might give you a new perspective on every sweaty run, humid walk, and brutally hot afternoon ride you’ve suffered through.
What is heat acclimation training? Heat acclimation training may sound fancy, but it’s simply the practice of deliberately exercising in hot conditions so your body learns to handle heat more efficiently. It sounds straightforward, but what’s happening physiologically is anything but simple.
When you first exercise in the heat, your heart rate spikes, you fatigue faster, and even easy efforts feel hard. But you body starts to adapt in remarkable ways when you begin to do it consistently. “You begin to sweat sooner and you sweat more, and your sweat is less salty, so your sweat evaporates better,” Gifford says.
Additionally, the volume of your blood plasma expands. You also begin to make more red blood cells and your hemoglobin increases, allowing you to have a higher oxygen-carrying capacity. The process is akin to your body tuning up its cooling system.
The best part is that all of our bodies are able to adapt like this. “Think about how an 85-degree day feels in May versus how that same temperature might feel in August. In May, it’s brutal. In August, you’re like, oh, what a nice day. That’s because you’ve become heat adapted, just by being outside,” Gifford explains.
How elite athletes use it For athletes competing in hot climates, heat training isn’t optional. For example, riders in the Tour de France often have to complete the 21 day race in the summer heat. Without previous exposure to heat, the athletes may not be able to finish.
Other athletes have to prepare for varied climates on the day of their event, meaning heat training is an important aspect of a broader training program. Gifford points to the Boston Marathon as a perfect real-world example.
“It can either be 50 degrees or it can be 75 degrees, and those are two totally different situations. If you’ve been training all winter and suddenly it’s an 80-degree day that you’ve never experienced before in your training, you’re in trouble.”
But, if runners deliberately add heat sessions to their training block before race day, the heat on an 80-degree day is a known quantity rather than a shock to the system.
How you can use it Heat training for elite athletes may seem intense, but the resilience gained from heat adaptation can benefit people of all ages and fitness levels.
“Heat adaptation means that the next heat wave or hot spell is less taxing on you,” Gifford explains. “That becomes relevant for athletes, like football players, but also for older people, who are much more vulnerable—less thermally flexible, let’s say. But with a little bit of heat adaptation, they can handle those hot days better.”
The best part about heat training is that anyone can do it. If you have access to a sauna or steam room, that’s a great way to start. But you can also heat train by taking walks in the summer sun, wearing extra layers while working out, or even taking a hot bath.
When you are starting, be conservative about the amount of time you spend in the heat. Pay attention to how you feel, and build gradually. The adaptation begins within the first few sessions and compounds over time.
For those who want to be more intentional, Gifford suggests using a core temperature sensor. He said being able to check his body temperature and see that it was still in normal range made him feel safe when doing his own heat training.
The takeaway Heat training may sound miserable to some, but the goal isn’t to suffer. It’s to lean into discomfort long enough that your body stops treating it as a threat.
So don’t think of your hot summer workout as a compromise. It might be the best training you do all year.
