Over the past few years, there have been a lot of interesting developments in endurance training, like the progression of the minimal vs. maximal shoe debate, watches with greater power than the computers that sent humankind to the moon, and more thoughtful use of sprint work. Yet very few coaches and athletes have investigated heat training. Even if you’re aware that this is a thing, perhaps you haven’t had the time to look into best practices, or your athletes are pushing back. I caught up with Alex Hutchinson, author of the bestselling book Endure and creator of Outside’s Sweat Science human performance column, to find out what the latest science suggests, get a compare-and-contrast of altitude and heat training, and obtain some guidelines for getting started.
[disclaimer: make sure your athletes consult a doctor before beginning this type of training.]
What are some of the physiological adaptations that can result from heat training?
You’ll start sweating sooner, which is a good thing because that means you can keep your body temperature lower, as sweating is a way of getting rid of excess heat. Your perception of temperature will also change, so you won’t feel as overheated at a given level of heat. The perception of how hot or cool you are is important because it’s one of the things that’s going to influence what sort of pace you can sustain.
There are also some more subtle changes that will occur. One is that your plasma volume will increase. Endurance athletes tend to focus on their red blood cells, which carry oxygen from the lungs to the muscles. The other part of your blood is plasma, which carries these red blood cells around the body. Increasing the volume of plasma helps you ferry blood to the periphery, to your skin and away from the core of your body, which helps you stay cooler. It might also help deliver more oxygen to your muscles, though that’s still up for debate among researchers.
What are the differences between wearing extra clothing while you’re training and getting in a sauna or hot tub?
Using a sauna or hot tub to keep your core temperature high after your session is one way to avoid the negative effects of putting on a bunch of extra layers, like running more slowly and compromising the quality of your workout. A hybrid approach would involve going out for your run or ride and then getting in the heat for 20 to 30 minutes afterward. This way, you’re getting the best of both worlds—a high-quality training session and a sustained increase of your core temperature, ideally somewhere around 101 degrees.
Scientifically, what is the ideal protocol for this kind of heat training?
If you look back at the early studies, it was an hour a day or more for ten to 14 days, six or seven days a week. But now the realization is that, yes, that maxes out your heat adaptations, but at what cost? So people have been trying to find shorter or more intermittent protocols. The simple answer to your question is probably that more is better. But you have to balance against the extent to which more is worse and pick something sustainable based on what sort of thing you’re training for, what type of training you’re doing, and being cognizant of the fact that if you try to do all your training in a really uncomfortable heat state, you’re probably going to lose something – both logistically and from a training quality perspective.
What did the University of Oregon physiologist Chris Minson discover when he was training Dathan Ritzenhein for the Beijing Olympics marathon?
They were preparing with the expectation that it’d be really hot on the day of the marathon. This meant implementing a more precise and scientific version of the approach Benji Durden took to heat training in the 80s when he ran covered in garbage bags. But then a thought struck Minson: What if it was a cool day instead? Would all that heat training actually make Ritz’s performance worse? So he conducted a study with three colleagues, which was published in 2010. It concluded that runners who acclimatized with heat training still got a lot faster even when testing in cooler conditions. This kickstarted a whole new wave of heat training-focused research.
With this in mind, what would you recommend that coaches suggest to their athletes?
With the caveat that the exact protocol depends on a lot of factors, you could do your normal endurance training sessions and three times a week, get in a sauna or hot tub for 20 to 30 minutes afterward. Continue this for two weeks, building up the amount of time you spend in the heat without becoming too uncomfortable.
Should coaches have their athletes taper heat training before a competition?
The rate at which heat adaptations decay remains contested and uncertain. But if you’re going to finish your heat training block more than two weeks before a competition, then you would probably want to think about incorporating some maintenance, like doing a heat session once or twice a week, to make sure you don’t lose all of the adaptations before your race. Though, that depends, as athletes who are competing in a hot climate and arrive before the competition will still be exposing themselves to heat.
How did Bob Larsen’s training group utilize heat exposure with Meb Keflezighi, Deena Kastor, and other runners?
“What Larsen and the other coaches were aiming for was to help Meb and their other runners acclimatize to what they knew would be a hot, grueling Olympic marathon. He was also an early Western adopter of altitude training up in Mammoth. We can see from the result Meb had at the Olympics, and Deena achieved in some major marathons that his approach was successful, even though heat and altitude were merely two variables in a complex program developed by this experienced coaching staff.
That’s not to say this approach will work for every coach or athlete. It depends on what your goals are and what you’re willing to do to reach them. You also need to understand that for every factor you tweak, there will be both benefits and costs. It’s not a one-way street.”
What are the benefits of using a hybrid approach that combines regular training runs followed by heat exposure?
“The challenge with having runners wear all these layers is that it’s going to feel uncomfortable, they’re not going to be able to sustain close to their usual pace, and they won’t be able to go as long as they normally do over any given distance. What some of the research now tells us about heat exposure is that keeping core temperature elevated is one of the biggest factors in driving adaptation. You don’t have to bundle your athletes up in sweatpants, jackets, and hats to achieve this.
Rather, have them do their normal session and then get in the sauna afterward. This way, they keep the quality level of each run high while also raising their core temperature for long enough to get the desired impact. It’s a different way of trying to achieve the same goal and one that athletes might find more pleasurable than if they’re forced to put in mileage in multiple layers.”
Outside of the physiological advantages, like being able to better tolerate the heat for a summer race, are there some potential health benefits of heat exposure?
“Some Scandinavian studies suggest so. Most of the bang for your buck here is going to do with the way heat increases blood flow and circulation. We see in several long-term studies that participants who used the sauna four times a week or more reduced their risk of heart attack, stroke, hypertension, and other cardiovascular diseases. The heat promotes circulation, which is probably the root of the lower incidence of these types of illnesses.
Chris Minson also has a paper in which he looked at an acute heat exposure protocol and how it moved the needle in the right direction for blood pressure. But we need to be cautious in making too much of these kinds of studies or the 30-year Finnish ones because there’s no consensus.”
I’m guessing there were other lifestyle factors at play in the vitality of those Finnish folks, too, right?
“For sure. We can’t simply say, ‘They’re healthier just because they use the sauna.’ It’s likely something they tried, enjoyed, and made them feel good afterward, so they made it a part of their daily routine. It’s probably a social thing they do with their friends and family members as well, which we know can benefit your health. If you like getting in a sauna or hot tub, then by all means, make it a regular part of your life. In which case, there’s no need to taper off as we discussed earlier or to only view this as a training methodology that you’re going to pursue for two weeks and then stop.”
