So engaging in deliberate heat exposure from something like a sauna, or even hot tub, hot bath, there's a lot of physiological adaptations and effects that happen that are very similar to aerobic exercise. And those things are like increased heart rate. You're getting increased plasma volume, you're getting increased stroke volume, you are getting hot, your core body temperature is elevating. So you sweat to cool yourself down. There's a lot of similarities between deliberate heat exposure from the sauna and more moderate-intensity exercise, I would say. Your heart rate can go up to about 120 beats per minute. Some people can get it up a little bit higher, particularly if they go in right after a workout.

But there's been head-to-head comparisons of moderate-intensity exercise and sauna use. It's really like the studies have shown they're pretty comparable. When you're doing the activity, heart rate goes up, your blood pressure goes up while you're doing the activity, but then after the activity, whether it's exercise or sauna, you're getting blood pressure improvements, your resting heart rate is improved, and these things are comparable. Really, in some way, I would say engaging in deliberate heat exposure from the sauna is mimicking moderate-intensity aerobic exercise.

There have been observational studies and some intervention studies we'll talk about in a second, but observational studies, Looking at people that are— and this is in Finland where saunas are pretty ubiquitous and most people are using them. So people in Finland that have sauna or using sauna and they exercise have a better cardiorespiratory fitness than people that exercise alone. And we're talking about, you know, same volume of exercise. And these people are the ones that do that, but also sauna, had a better cardiorespiratory fitness than people that only engaged in exercise. And then there's been intervention studies by Dr. Jari Laukkanen that have shown— so he's taken untrained people and put them on an exercise protocol. It was a stationary bike.

And then he had 2 groups, one that just did the stationary bike with passive recovery and the other ones that did the stationary bike, but then they went right into the sauna for 15 minutes. And he looked at a variety of parameters, one of them being VO2 max. So what he found was that those people that did the the exercise bike and the sauna had a better VO2 max than the ones that only did the exercise bike. And to me, that makes sense because again, it's almost like extending the workout. You're extending it just a little bit more. There were also better improvements in blood pressure and other lipid parameters as well in the group that also added a sauna plus the exercise. So I think there's benefits to deliberate heat exposure for people that are physically active.

But also, you know, people that are not, people that are disabled, people that can't get on a bike, people that can't go for a run, people that can't do a burpee, they can get into a sauna and get somewhat of that cardiovascular benefit. And there's all sorts of observational data out there looking at people that use the sauna 4 to 7 times a week. They have a 50% lower cardiovascular-related mortality, 40% lower all-cause mortality, and it goes on and on. So I think there's a lot of utility there for people that really just can't go and work out as well. So another really important adaptation that happens when you are engaging in deliberate heat exposure for something like the sauna, also a hot bath, is the increase in something called heat shock proteins.

And these are— this is an adaptive response. So as you're elevating your core body temperature, you're getting hotter, these heat shock proteins are activated and they are— the main role that they— the main function they serve is to prevent proteins from aggregating and forming plaques in your cardiovascular system, in your brain. In fact, there's been multiple animal studies showing that if you give a mouse like an amyloid beta plaque, sort of what we get with humans in Alzheimer's disease, and you express the heat shock proteins, make them highly expressed, that they don't get the Alzheimer's-like symptoms and it helps with the plaque aggregates and stuff. So heat shock proteins play an important role in preventing protein aggregation. They have somewhat of an antioxidant effect.

They're also very important for slowing muscle atrophy. And this is, again, has to do with a variety of mechanisms. There's been a lot of animal studies on this, but there's now been some human data where people, you know, there's intervention trials where they're, you know, engaged, they basically immobilize one of their limbs for a period of weeks and then did some local heat exposure. And the local heat exposure prevented the disuse atrophy by like 40%. So, you know, I think that's a very relative, again, a very relevant way for people that are injured or again, people that are older and, They're experiencing a lot of muscle atrophy as well.

But there was also a very recent study, and this is small, so it needs to be repeated, but people that were engaging in resistance training either just alone or then went into the sauna right after the resistance training, they had greater gains in muscle mass if they went to the sauna right after the resistance training compared to resistance training alone. Well, they actually— it was biomarkers of it. So, they didn't directly measure muscle mass. It was biomarkers. But anyways, I think it's an encouraging and promising area that, of course, I'm excited about. I'm glad people are out there researching. But it's another possibility for a synergy between resistance training, between vigorous intensity exercise, your exercise program, and then engaging in deliberate heat exposure as well.

So what are the parameters in a lot of these studies? Well, a lot of the parameters in many of these studies are coming out of Finland. The temperature is about 174 degrees Fahrenheit, and the duration spent in the sauna is about 20 minutes. And that's important because people that spent less than 20 minutes, like let's say they were in there for 11 minutes, they didn't have the robust effects. So it really is a temperature-dependent, duration-dependent, but also frequency. So how many times a week, you know, people are getting in the sauna. For anything to occur, 2 times a week was like the minimum effective dose. So if people did something twice a week, it was more beneficial than once a week. But people that did 4 times a week, 4 to 7 was really the most robust effects.

So if you're looking for the most robust effect, the minimum time would be 4 times a week, you know, compared to 1 time a week. The humidity is usually around 10 to 20%. And the question a lot of people ask is, well, what about, you know, what kind of sauna? What if you don't have a 175-degree sauna? What if you have an infrared sauna that goes up to 145? Like, is that— can you get comparable effects? Again, temperature, duration dependent, right? So, you're not going to get the same effect in 20 minutes in a 145-degree sauna in terms of the heart rate and the cardiovascular adaptations as you're going to get in a 180-degree Fahrenheit sauna, right? So, you might have to stay in there twice as long. You might have to stay in there 45 minutes to an hour to start to get your heart rate up.

Again, you can wear some kind of heart, you know, wearable heart rate measure. device where you're looking at your heart rate and you can feel it, like, when it starts to go up. Sometimes it'll take a long time in an infrared sauna. There are studies out there that have compared regular hot saunas to infrared in terms of cardiovascular benefits, and if the same volume of time is spent in there, you're not going to get as robust of an effect on blood pressure improvements as you would with a regular sauna. So again, you might have to spend more time in there as well. Hot baths have also been shown to increase some of these biomarkers like heat shock proteins that sauna has.

And I really think that's a really good— the fact that it's able to increase some of the same biomarkers, to me, signals that maybe hot baths or any sort of modality that's really increasing your heart rate, that's making you hot, is something that's going to be beneficial as well. So I do think that people that don't have access to a sauna could do a hot bath, get one of those little pool devices that measure temperature, put it in your bath, and keep it up to 104 degrees Fahrenheit and be in there for 20 minutes, because that's what the studies have shown. 20 minutes at 104, shoulders submerged all the way down. And then the other question is, well, what about is more better? So here, I'll give you my take, then I'll tell you about one study.

I think that when it comes to the— we're stressing our body, and this kind of goes back to this lady's question as well. I mean, heat stress is a stress, right? I mean, hyperthermia is a real thing. Like, you can get damage from too much heat. So it's important to keep in mind that there's always like a window of you're engaging in this kind of stressful activity, like physical activity or deliberate heat exposure to have this response. It's an adaptation. Some people call it a hormetic response to have the anti-inflammatory benefits, the antioxidant benefits, all the adaptations that happen. But when you make that stress too high, then it's hard to counter that stress with our adaptations, right? So when you're going in a 200-degree Fahrenheit sauna or 215 or whatever, it is very hot.

And there are studies, animal studies and stuff, like when you get too hot, you can actually permeabilize the blood-brain barrier. And so I know it's like there's this go hard, there's always this push, like, and if you're that kind of person, you're like, well, I give it my all. There's one study, this was not out of Dr. Jari Laukkanen's lab, it was another study. I can't remember if it was Poland, might have still been Finland, it was Finland or Poland. But they were looking at a variety of temperatures and dementia risk and Alzheimer's disease risk in people that use the sauna. And it repeated what Dr. Laukonen had found.

So people that use the sauna frequently had a much lower risk of dementia and Alzheimer's disease, but only if they weren't getting in a sauna a sauna that was over 200 degrees Fahrenheit. If they were getting in a sauna that was over 200 degrees Fahrenheit, they were actually having the opposite effect. And I don't talk about that a lot because it's not really understood why, and I don't want to, like, people to get scared, but I do think it kind of highlights the role of, like, why do you need to go in a 215-degree— like, have you— it's so hot, you know, and your brain is in there. Like, so I don't think that going in a 200-degree Fahrenheit sauna is the way you have to do it.

I think you can get in 180, 185, if you really want to go 190, yeah, but maybe stop before it gets to 200 degrees Fahrenheit. So is it fair to say that 174-ish is like the sweet spot or is it very— Well, yeah. So the question is, is 174 degrees Fahrenheit the sweet spot? That is the average temperature that people in those studies were using. And I typically do around 175, 180, and I do put water on the rocks to make steam, which makes it hotter. And I usually do it after workout, so I'm already hot. I already have my heart rate elevated. So yeah, I mean, doing 30 minutes at 175 degrees Fahrenheit is nice. I think it's safer for the brain. I mean, you're getting a lot of the benefits. Studies have shown that 30 minutes at 163 degrees Fahrenheit increases heat shock proteins by 50% over baseline. So I don't know that you have to go to 200 degrees, and I don't know that you should, to be honest.