Transcription
[Music] medcra.com. Welcome to another MedCram lecture. Today, we're going to talk about hot tubs, traditional saunas, and infrared saunas. And specifically, we're going to look at a study that compared these three modalities in terms of how well they could raise core body temperature and have some of the endstream effects that we see from core body temperature, like for instance, the effect on cardiac output and also cytoines.
I realize that that's not the reason why we always do these modalities, but it's one of the big areas that we like to see in terms of the end effect, like what effect does it have on core body temperature? And we've talked about that here on MedCram. We had a number of videos. Probably one of the most prominent was this one called interferon COVID and hydrotherapy with new studies. We showed that as the core body temperature goes up, there's a huge increase in interferon. We'll actually be talking about some of the end organ effects of cytoines. Interestingly, interferon was not tested in this study, but a number of other ones were. We also talked about the use of heating up core body temperature, not just in terms of the history of it, but also the history in terms of the last pandemic and how it was found to be beneficial and at least some observational studies. So, it's actually an important topic, especially if you're doing sauna, infrared sauna or hot tubs for health purposes.
There is a number of studies that have come out showing that interferon response is actually mitigated and controlled by a number of enzymes and proteins, all of which get upregulated right when you hit 38° C. All of these red arrows here are all regulated by enzymes that go up. And in fact, it was temperature alone that was sufficient to increase phosphorilation, activation of stat 2, stat 3 in these in vitro cells which led to an increase in interferon and its binding to the receptor. This is a really good topic to review and this is one of the few where I've seen actually a head-to-head trial with really good controls. We'll talk more about that, but first just want to remind you, join us at medcram.com for continuing medical education for providers, but also for patients, people who want to know more about their body in terms of ECG interpretation, looking at your chemistries on your my chart, medical acid base, looking at chest X-rays and interpretation, acute renal failure, sleep apnea, and the list goes on and on and on. This education is not pharma sponsored and so if you want to sponsor this type of educational experience, please support us by joining us at medcram.com.
Let's jump into the study. This was published in the American Journal of Physiology, Regulatory, Integrative, and Comparative Physiology. The title of the study was comparison of thermo regulatory cardiovascular and immune responses to different passive heat therapy modalities. And specifically, they looked at hot water immersion. As you can see, there's HWI. This is like the hot tub. There is traditional sauna, which is abbreviated as TR R A D or TRAD. And then there's far infrared sauna, which is abbreviated as FIR. And some of the things that they looked at was core body temperature, skin temperature, sweat loss, heart rate, mean arterial pressure, cardiac output, stroke volume, systemic vascular resistance, and whether or not there were cytoines that increased. Now notice that interferon is not one of these, but there are some other ones that we will talk about here.
This is a busy page. Let's go over it very carefully. This was a visit to the laboratory. Each subject was a control for all of these different modalities. So each subject came back and did a hot water immersion, a traditional sauna, and a far infrared sauna. So that way if there was any differences between the subjects, it wasn't going to matter because all of the data was pulled. Furthermore, each of the data was separated by a week and it was in random order. So when they came in, they rested on their back. There was blood that was drawn 5 minutes before either the sauna or the hot tub or the infrared sauna was started. And then they started it at 0 minutes.
So what did they do for the hot water? They just submerged them for 45 minutes in water that was 40.5 C or 104.9° F and it was constant across the board. They were up to their mid sternum. One of their arms was out of the water and that's what they checked the blood pressure on. The upper extremity was out. Sometimes people ask, you know, how deep that they go. That was what it was.
For the traditional sauna, they started there 10 minutes at 80° C or 176 degrees Fahrenheit. The 176 was not the measured temperature, but it was the set temperature on the actual sauna. They went in there for 10 minutes and then they came out after 10 minutes and rested for 5 minutes at 22° C or 71.6° F. They put two ladles of water on at the beginning to increase the humidity to 40%. After that five minute break, they went back in again for 10 minutes, rested for five, back in again for 10 minutes, and rested for five. So that's basically 15* 3. When I do traditional sauna, I usually don't spend just 10 minutes. I usually spend about 20 minutes before getting out and doing a break or a rest or a cold plunge or something like that. When I looked this up, it could be anywhere between 5 and 20 minutes. This is in the mid-range of this. I think what they were trying to do is to just see minute form minute based on how people do these modalities how well would it have worked. I know that there's going to be some criticism on how they did the protocol for the traditional sauna but nevertheless that's what they did. They measured at 0 minutes at 22 minutes and then again at 45 minutes in terms of cardiovascular output and then at 65 minutes post 20 minutes after they got out at 45 they did another blood test. They did another blood test 24 hours later and another blood test 48 hours later.
What did they do for infrared? Set it to 46 increasing to 65 by the end of the heating for 45 minutes. Started at 114.8 and went up to 149. This would be on the plug-in device that comes with the infrared sauna. That's not what it was actually measured. I'll show you that. What did they do again? They took blood tests before and they took measurements of cardiac output during blood tests at 65 minutes, 24 hours, 48 hours during the spine recovery.
How did they actually measure? There's things that you need to understand in terms of temperature. There is the mean temperature which is a combination of skin temperature and core temperature. So core temperature is in the middle and it is usually measured by either a rectal probe which six subjects decided to do or by an oral telemetry pill which actually can transmit the temperature from literally inside the body. 14 decided to go with that one.
There was 10 males and 10 females. Let's go back and take a look at that and see who the participants were. On average they were 24 years old. So these are young. There was 10 females. There were 10 males. You can see what their height was in centimeters and what their weight was in kilograms and what their body mass index was. It was a little bit overweight, greater than 25. The heart rate resting was 70. Systolic blood pressure on average was 117 over 75. So not hypertensive.
What's interesting about this and which may cause some issues and I didn't know that this was an issue to be is that in the traditional sauna when they actually set the temperature to 78° Celsius 172° F this was the factory setting mean during the study when they actually measured it with an independent thermometer the mean was actually more like 66° C or 150° F. So, that's a significant departure and actually cooler than what we should be getting or what we thought we would be getting just using the thermometer that comes with the traditional sauna. Same thing happened, by the way, for the infrared sauna. They set it for 57° C, which is 134.6 Fahrenheit. The mean when it was actually measured was 45° C and just 113° F. I don't know if this is a thing with the industry where they are overestimating the temperature or overmeasuring the temperature in these saunas. I guess one recommendation is if you have a infrared sauna or a traditional sauna, make sure you're independently assessing the temperature where you are sitting in that box and seeing what the actual temperature is.
Let's take a look at data and see what happened in terms of the different endpoints. Let's look at core body temperature. This is the temperature specifically of the internal organs. They are strictly regulated. And as you can see here with the open circles. This is the hot water immersion or the hot tub. And you can see that it had the most change going up well above fever which is 38.0. And I might add, as we showed at the beginning, well above the threshold where we would see an increase in the regulatory enzymes for interferon. None of the other modalities actually reached that standard. You can see here that the traditional sauna did go up more than the infrared sauna, but not as much as the hot water immersion. So based on this and the protocols that they came up with, the most effective way of raising core body temperature is going to be hot water immersion. And you can see they're right at the 45minute mark and how things started to come down after that. Interesting in the infrared sauna, things started to still increase. Again, I'll say this over and over again. The purpose of infrared sauna is not just elevating body temperature. Of course, as we've talked about extensively on our channel, there are benefits to infrared light on the human body. Unfortunately, really nothing in this study actually looks at any of those end points, oxidative stress. This is looking at cytoines as a result of elevated body temperature.
That was core body temperature. Let's go to the other extreme, which is skin temperature, which is measured on the outside of the body. traditional sauna and the steam up to 40% there on those three 10-minute spots. You can see here it starts at baseline, goes to about 10 minutes right there, and then they cool off for 5 minutes as it comes back down, goes back in for 5 minutes, and then back down, goes back in for five, 10 minutes, and then back down again. So, you can see that there's a lot of variation in terms of skin temperature in the traditional sauna. When we look at the infrared sauna, it just goes up and even though it hits 45 and then starts to come down, comes down there after recovery. When we look at hot water immersion, it jumps up pretty quickly within 5 minutes and then slowly starts to go up again. If we look at this in terms of skin temperature, it seems as though if you were to stay in a traditional sauna and not get out for 10 minutes, you probably would get better skin temperature in a sauna than you would in a infrared sauna or hot water immersion.
Mean temperature is this equation, which is a weighted average more towards core with about 20% variation for skin. And you can see here that the mean temperature is going to be somewhere of a tie between hot water immersion and traditional sauna. Again, we're not seeing a huge increase there in terms of the infrared sauna.
Let's take a look at sweat. They measured each of these subjects completely nude before and after so they could see exactly how much sweat they lost cuz it's almost impossible to tell when you're submerged in water. As it turns out, there was the most amount of weight loss when there was hot water immersion followed by traditional sauna and then ending up at infrared sauna. You can see that pretty clearly.
In terms of heart rate, what's going to happen when you have heat is you're going to have vasoddilation. And when you have vasoddilation, that means the tubes that your heart is pumping the blood around in are going to get bigger and the heart is going to have to pump faster and harder. And so, it's no surprise that we would expect to see the heart rates go up. And in this case, because core body temperature is going up the most, we're going to see the biggest increase in the hot water immersion, followed by the traditional, which jumps around a little bit more, followed by the infrared sauna.
When that heart rate jumps up, it's because the blood pressure is dropping because vasoddilation globally because of heat temperature. And so the modality that's going to have the biggest temperature jump is going to cause the vasoddilation maximum. And that's why we see here that the mean arterial pressure drops the most with hot water immersion. So with that vaso dilation, you would expect to see a larger cardiac output in hot water immersion. And that's exactly what we see. We see also the stroke volume going up. So the heart is pumping more strongly and bigger proportions of volume. And then the resistance because of the vasoddilation, it's going to drop and it's going to be the lowest. That's exactly what we're seeing.
So let's talk a little bit about the effect of this elevated temperature on the cytoines of the human body. And again unfortunately they did not look at the effect of heat on interferon. They looked at IL6 which is a inflammatory cytoine also tumor necrosis factor alpha and then IL1. So IL1 IL6 tumor necrosis factor alpha. And the take-home here is that there was no statistical significance anywhere for any of these saunas, traditional or otherwise. The only statistical significant difference that they saw was at baseline versus post in IL6. And that is it.
In terms of cells, CD4 counts went down with hot water immersion, but no statistical significant differences with traditional sauna or infrared sauna. there was an increase in CD8 positive cells which are responsible for killing cells that are infected. You can see that there no statistical significance with either traditional sauna or infrared sauna. And also the percentage of CD16 positive and CD56 positive was statistically significantly increased going from baseline to 24 hours. But again, no difference in terms of the sauna.
I don't want to seem to be ragging here on sauna, but there could be different endpoints that are more beneficial. In this case, what we're looking for is core body temperature change and downstream effects of that core body temperature change and increase in regulation of these cytoines.
So, I want to read some of the conclusions and perspectives from this study. They say here, it is well known that heat therapy in the form of hot water emerging can lead to beneficial adaptations in cardiovascular health by lowering blood pressure. as we talked about here, improving conduit and microvascular endothelial function. So this is really important and reducing arterial stiffness. In addition, repeated exposure to far infrared saunas in the form of weon therapy as well as traditional saunas have been shown to reduce all cause mortality and improve cardiovascular function, endothelial function and peripheral artery disease. The present study found that a single bout of hot water immersion leads to the greatest physiological challenge compared to both sauna modalities. So, we're not saying that sauna doesn't work. We're saying that in terms of the extreme and core body temperature, it seems as though 45 minutes submerged in a hot tub at 104.9° F is more beneficial than if you just set your sauna to particular degrees and hope that it actually is there.
So there's a number of interesting caveats here and they say that the caveat, however, is that we focused on the acute effect of heating in a young healthy population that was recreationally active. Individuals who regularly engage in endurance exercise and thus have higher aerobic fitness exhibit an enhanced heat loss capacity via adaptations for exercise training. For a comprehensive review on the effect of endurance exercise on thermmorreulatory adaption, readers are directed to review by period at all. And that's reference 88. By the way, we'll give you a link to this study in the description below.
They say, "Therefore, further research should explore how various patient populations respond to different forms of passive heating, both acutely and chronically, specifically in populations that are unable or unwilling to exercise. This will help identify which modalities are most suitable for specific clinical populations, ultimately guiding clinicians to the potential prescription of heat therapy for the treatment of prevention of disease. I think this is really key here. This is really underrated. There is actually a lot of benefit. The first lowhanging fruit here is the understanding that perhaps Tylenol should not be given for every temperature greater than 100.4 or 38° C.
They say in addition, the optimal doses and durations of heat exposure for each modality remain unknown. Determining the heating intensity and duration required for each heating modality to induce significant changes in core temperature and cardiovascular strain similar to exercise is crucial given the distinct properties of different healing modalities such as the comparisons are challenging. In addition, socioeconomic and other societal considerations need to be evaluated. For instance, saunas are going to be a little bit more expensive and a little bit more challenging than a hot tub. So that needs to be taken into consideration. They say by way of example, access to saunas may be more challenging for many people throughout the world. Identifying the most effective dose for each modality will enable heat therapy to be more effectively utilized as an alternative to exercise, promoting health and reducing disease risk or severity.
In terms of conclusions, they say, "This study indicates that a single session of hot water immersion leads to the greatest physiological strain compared with both traditional and far infrared saunas. Due to the unique environmental challenge imparted by whole body water immersion, we know that water has a specific heat that is pretty large, which means that it's going to take a lot of energy to elevate the temperature of water. But also as the temperature of water decreases it gives off a significant amount of heat. Heat that can actually increase the body temperature of the human body. They say here that the large increase in core temperature elicited by hot water immersion results in cardiovascular strain and imunological alterations which may lead to beneficial health adaptations with repeated exposures. All physiological responses were far less robust with saunas in a commercially available sauna unit. Further research is needed to determine whether these findings hold true in clinically relevant populations.
So in terms of grants, there was no agenda here. There was not funded by the hot tub association of America. No disclosures that were relevant.
Let's talk about infrared light. This is not a defeat for infrared light saunas. The point of those infrared saunas is not necessarily to get your body temperature up, although it can do that. There is a benefit from looking at near infrared light and their effect on the mitochondria in terms of reducing oxidative stress, increasing ATP. We do see an increase in carbon dioxide production and a reduction in glucose. We did not see any kind of end points in this study related to infrared light. If we had measured things like glutathione or F2 isoprostane, these are things that are involved with oxidative stress, this may be a different story in terms of output. But that's not to say that just core body temperature is not important. As we've shown multiple times, elevating core body temperature seemed to have a benefit, at least observationally, as pointed out by Dr. Rubble at the New England Sanitarium on the East Coast around Boston. By the way, a Nobel Prize in medicine in 1927 was awarded because of just such properties of increasing body temperature. This time in patients who were given malaria that actually cured people of their neurosyphilis and this was awarded by Wagner Yore in 1927. But you got to realize that it's labor intensive.
Here's another modality that was not even tested in this study looking at the ability of hot fermentations. This is basically hot towels that are soaked in water and heated up and then applied to the patient as to not burn them but to elevate their body temperature. And you can see here that labor intensity is there. Quite frankly, it's easier to give a pill if there is one available. And the key there is if there is one available.
There you have it. Those are the three modalities. Some might say for the hot tub at 104.9 that it is very difficult in the United States to get saunas up to anything greater than 104 since that's sort of the maximum. There are ways of doing that. There are ways of modifying to do that and there are a number of YouTube videos that you can search out in terms of how to do that. I think it would be really important if you've got a sauna to make sure that the temperature that you're setting it to is the actual temperature that you're getting. And that's as simple as just purchasing a relatively up-to-date and appropriate thermometer.
Well, I hope you've enjoyed this video where we have reviewed some of the data that has been obtained from the comparison between hot water immersion, traditional sauna, and infrared sauna. If you found this helpful, there is more continuing medical education at medcram.com. Please join us there, subscribe, and support this type of education. Thanks for joining us. [Music]