Thermal Stress Is a Signal, Not a Shortcut
Saunas and ice baths sit at the center of modern recovery culture. The better question is not whether they are fashionable. It is whether heat and cold give the body a meaningful signal to adapt.
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Can Sauna & Cold Exposure Offer Similar Benefits to Exercise? | Sharon Bergquist | EP # 365: Full Transcript
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Sauners and ice baths all the rage right now. Yes. I love that you're coming at this from a scientific perspective. What do we need to understand here about exposing oursel to hot and cold? What's happening at a cellular level? And how do you want people to think about this and and consider it in their own life? Yeah. So I again view this from the perspective of hormesis and heat and cold are thermal stressors. They throw our bodies out of balance. So our body has a natural temperature that's roughly 98. 6 ° F or 37 ° C. When we are exposed to cold, our core body temperature drops. When we're exposed to heat, our core body temperature goes up. And that kicks in all these feedback mechanisms that our body uses to reestablish that homeostatic temperature where our enzymes function optimally. In that process of our body kicking in these um responses, we activate these cellular stress responses that start the repair processes, the um uh clearance of damage from our bodies. They reduce inflammation, reduce oxidative um damage. So these protocols for heat and cold are helping us at a cellular level um achieve a lot of these repair and regenerative functions. Um so I I think that they're promising from that standpoint. Um they're also physiologic benefits to each of them. Uh, for example, with cold exposure, um, our body responds to cold by turning on this internal space heater we have called brown fat. And brown fat is very
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brown fat. And brown fat is very metabolically active. And what's really kind of fascinating is whereas white fat stores energy, brown fat is trying to break it down, it's utilizing fats and glucose to generate heat. Um, so there's a lot of interest in can we use brown fat to improve our metabolic health kind of breaking down our stores just as fasting or exercise would do. Um, and um, I think that's hugely interesting. Most of the increase in our metabolism that happens through cold exposure happens from muscle shivering. we simply just have so much more muscle mass than we do brown fat that a lot of the improvements to our metabolism are coming from the muscle shivering as opposed to non-shivering thermogenesis. Um but nonetheless I think um this is a really exciting area. Um and I think we're going to see a lot more studies right now. There's a lot of association studies that people who have more brown fat tend to have lower BMIs. their um association studies as well with different lipid parameters, but I think we're going to um use potentially see more as brown fat as something that can be used in different capacities to help our metabolic health. Heat I think we have stronger data on than we do with cold. Um part of that is because with heat um the protocols are much more consistent. Um they're generally sauna protocols um with longitudinal data. With cold there are usually smaller studies, many different protocols, it's very hard to make strong generalizations. With heat, um it mimics exercise. Um when our bodies are trying to dissipate heat, sweating is our internal air conditioner. and our body is trying to shunt blood to our skin where we can evaporate the heat. In that process, our
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evaporate the heat. In that process, our heart rate goes up and we can mimic really moderate to high intensity exercise. So our heart rate can be anywhere from 20 to 150 beats per minute from sauna exposure. And that process creates a shearing force on our blood vessels. And that sheer stress from the blood being shunted towards the periphery um improves our endothelial function. The endothelium is that lining between the blood and our blood vessel wall. And we have like 60, 000 miles of endothelium. And as those um endothelial cells experience the sheer force, they release more nitric oxide. Nitric oxide is a vasoddilator. It reduces clotting ability in our um blood vessels. It reduces oxidative stress. It reduces inflammation. So it essentially is making our endothelial lining healthier which reduces our risk of cardiovascular disease. Um so there there's I think a lot of benefit to using thermal stress. Um I would say it's an adjunct again to diet and exercise. there's not a substitute, but I think a very overlooked way that we can improve our health. So perhaps first getting the phytochemicals into the diet, thinking about a 10-hour eating window, getting the highintensity exercise, and then from there, when those are in play and consistent with those, thinking about this thermal exposure. I can see people now, Sharon, thinking, "Okay, I'm going too fast. I'm going to wake up. I'm going to do my cardio. I'm going to go straight from my cardio into a sauna. And maybe before I hop in the sauna, I'll grab a broccoli sprout juice and stack stack all of these things together. You know, again, I think there's merit to each of these, but um you kind of
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to each of these, but um you kind of have to experiment a little bit. Certainly, if you um do a nice cardio workout, then go into the sauna, you can extend some of the benefits from the cardio workout. Um and you know, certainly for people who can't exercise, um sauna has a lot of benefit. Um I think with the way to kind of look at how do you incorporate these good stressors is start with one. um kind of get to where you feel that you your health is optimized. Like kind of track how you feel with each one. You want to push past your comfort zone but not to the point of overwhelm. Take time for recovery. Then introduce the next and kind of in that fashion stack the habits. Um and I think that collectively you can create a very healthy lifestyle by doing it that way. Is sauna something that you use personally? And if so, what does that look like in terms of number of times a week or how long do you stay in there? Yeah. Um, so my access to sauna is my limitation. So I I wish I had one in my home, but I don't. So my limitation is I I have to go to a gym to access sauna. Um, what is more practical for my daytoday is hot baths. Um and and I would say that for anyone listening who doesn't have fancy equipment that this is also a way to practically incorporate these good stresses in your life. So a hot bath between 102 to 104 ° um has a lot of the benefits we're talking about. that can activate heat shock proteins which is one of the mechanisms by which we're get a lot of the benefits from heat and um I do that um a couple times a week um as time
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um a couple times a week um as time allows um close to bedtime so that I can naturally um allow my body to cool off and that cooling off process helps with getting better sleep at night. And just to be clear that's 102 to 4 ° F. Fahrenheit. Absolutely. Yes. For my Australian listeners out there. Yes. We don't want you to get into 102 to 104 ° C. No. I am absolutely excited to share an exclusive offer with the proof community. This is a limited time offer just for my audience and no doctor referral is needed. Function Health is a comprehensive at-ome blood testing service that gives you access to over 100 biomarkers covering everything from heart, liver, kidney, and metabolic health to hormone levels, inflammation, and nutrient status. That, my friends, is five times more testing than the average physical. I chose Function for my own blood work and to be a sponsor of this show because they are the best in the world when it comes to helping you understand and own your health. It's true. The depth and quality of their testing is unrivaled. And as regular listeners of this show will know, you cannot optimize what you don't measure. Don't guess, test. Use function to know exactly where your health is today. And then intervene with evidence-based medicine and lifestyle changes to feel your best and reduce your risk of chronic disease. With function, you get access to very important markers like LP little A, a genetically driven cardiovascular risk factor. Apo B, the most predictive marker of atherosclerosis, and LH and FSH, reproductive hormones typically missing from standard lab panels. It's not uncommon for these biomarkers and others to be elevated. For example, over 50% of function members have an APOB level and over 20% have an LPA little level that is above the optimal range. You can even
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Transcript auto-generated by YouTube. Verbatim — duplicates intentionally preserved.
In this conversation, Dr. Sharon Bergquist frames thermal exposure through hormesis: a controlled stress that briefly moves the body away from comfort, then asks it to restore equilibrium with more resilience.
Hormesis Begins With Temperature
Heat and cold are thermal stressors. Cold asks the body to defend core temperature. Heat asks the body to dissipate it. In both directions, the stress is temporary, but the response can be constructive.
At a cellular level, that response activates repair pathways, helps clear damage, and can reduce inflammatory and oxidative pressure. In plain language, the body learns from the challenge. The felt result is a stronger sense of capacity: more alertness after cold, more softness and release after heat.
Cold Turns on the Body’s Internal Heater
Cold exposure can activate brown fat, a metabolically active tissue that uses glucose and fat to generate heat. Bergquist also notes that much of the metabolic work comes from muscle shivering, simply because muscle makes up far more of the body than brown fat.
This matters because cold is not magic. It is a demand. The body responds by producing heat, sharpening attention, and recruiting systems that are designed to protect temperature and function.
Heat Carries the Stronger Evidence Base
Bergquist is careful about the evidence. Sauna (this topic in depth) research is more consistent than cold research because the protocols are easier to compare and the long-term data is stronger. Heat can mimic some effects of exercise by raising heart rate and moving blood toward the skin.
That increased blood flow creates shear stress along the blood vessels, encouraging nitric oxide release. Nitric oxide supports vasodilation and healthier endothelial function. You feel it as warmth, circulation, and a calm fatigue that can support sleep.
Stack Stress With Restraint
The temptation is to combine everything: exercise, sauna, cold, fasting, supplements, and intensity. Bergquist offers a quieter principle. Start with one practice, notice how the body responds, recover well, then add the next.
A good stressor becomes useful only when the body can absorb it. Push past comfort, not into overwhelm.
"A good stressor becomes useful only when the body can absorb it."
Practical Takeaways
Use heat and cold as adjuncts to nutrition, movement, and sleep, not as replacements.
Treat sauna as the more evidence-supported thermal practice, while recognizing cold as promising but more variable.
Build one stressor at a time so adaptation has room to happen.
Words Worth Hearing
Use heat and cold as adjuncts to nutrition, movement, and sleep, not as replacements. Treat sauna as the more evidence-supported thermal practice, while recognizing cold as promising but more variable. Build one stressor at a time so adaptation has room to happen.