Benefits of Sauna Use

Sauna Benefits

  • Potential to increase longevity through a lower risk of cardiovascular related mortality and all cause mortality
  • Improves heart health through the lowering of blood pressure and increasing stroke volume (plasma volume and blood flow increases to the heart, making the heart do less work for each beat)
  • Activates stress response proteins known as heat shock proteins, which assist in maintaining protein structure and prevent accumulation of damaged proteins
  • Reduce risk of developing Alzheimer’s and dementia through the benefits of heat shock proteins.
  • Improves mood through the release of norepinephrine.
  • Reduce muscle atrophy through the release of growth hormone, which increases IGF-1, which is known to support muscle growth
  1. Potential to increase longevity through a lower risk of cardiovascular-related mortality and all-cause mortality
  • In a published study found here, it was found that:
    • Fatal cardiovascular disease was 27% lower for men who used the sauna 2 to 3 times a week and 50% lower for men who used the sauna 4 to 7 times a week compared with men who just used the sauna once per week.
    • Sauna use lowered all-cause mortality. Using the sauna 2-3 times per week was associated with 24% lower all-cause mortality and 4-7 times per week lowered all-cause mortality by 40%.
      • What it means: The people in the study had 40% less mortality than those of a similar age not being subjected to these same conditions and this reduction in mortality wasn’t strictly tied to heart disease
    • This study also adjusted for other lifestyle factors that may affect the data including body mass, serum cholesterol, blood pressure, smoking, alcohol consumption, type 2 diabetes, physical activity, and socioeconomic status
      • The study recruited over 2000 middle-aged men
      • Location: Finland
      • Goal: Determine how frequency of sauna use relates to sudden cardiac death, fatal coronary heart disease, fatal cardiovascular disease, and all-cause mortality including cancer
      • Lasted: 20 years
  1. Improves heart health through the lowering of blood pressure and increased stroke volume (plasma volume and blood flow increases to the heart, making the heart do less work for each beat)
  • Sauna use has similar benefits seen with regular physical exercise
    • Heart rate can increase up to 100 beats per min during moderate sauna bathing sessions and up to 150 beats per min during more intense warm sauna use.
    • Heat stress from sauna use also increases plasma volume and blood flow to the heart, known as stroke volume. This results in reduced cardiovascular strain so your heart has to do less work for each beat that it does to pump oxygen-rich blood to your tissues and brain.
    • Long-term sauna use has been shown to generally improve blood pressure, endothelial function, and left ventricular function.
  1. Activates Stress Response Proteins known as heat shock proteins. They help maintain protein structure and prevent the accumulation of damage protein.
  • Lower Alzheimer’s and Dementia risk through heat shock proteins
    • Heat-shock proteins are produced by our cells in response to heat stress (and cold stress). Sauna use robustly activates a class of stress response proteins known as heat shock proteins, and heat shock proteins have been implicated in aging, The increased expression of HSPs, it shown to have an association with longevity. HSPs help all other proteins maintain their proper 3-dimensional structure in the cell which is important for each protein in order for it to be able to perform its function. We have various interactions with our environment that can disrupt the structure of proteins in our body, denaturing it for example. This prevents the protein from doing its function and changing the half-life of it. Damaging products get created from normal immune system function and metabolism. These damaging molecules, produced at a low level every day even in the best of circumstances but made worse by poor lifestyle choices, damage proteins and disrupt their structure. Moreover, once a protein’s structure is damaged it can then misfold, preventing degradation and can lead to the accumulation of toxic protein aggregates that can themselves damage cells as well.
    • Protein aggregates, something heat shock proteins specifically helps prevent the accumulation of, are associated with neurodegenerative diseases such as Alzheimer’s disease and Parkinson’s disease and Huntington’s disease. When you take normal mice that have been engineered to accumulate amyloid-beta plaques (characteristic of Alzheimer’s), they do begin to manifest a pathology in the brain that is similar to what we might call Alzheimer’s in humans/ However, if you engineer these same mice to over-produce one of the more well-known heat shock proteins, HSP70, it reduces the severity of this condition, including reducing the associated loss of neurons and synapses.
    • We know that heat shock proteins are produced in response to heat stress, and they seem to help prevent symptoms of Alzheimer’s in mice by reducing protein aggregation and by helping keep proteins from losing their structure in the first place. What if, by naturally increasing our heat shock protein expression, we could reduce the risk of Alzheimer’s? The same group that studied over 2000 male sauna goers found a very interesting association from the same cohort that they later published in another paper: they found that men that used the sauna 2-3 times per week had a 22% lower risk of dementia and a 20% lower risk of Alzheimer’s disease compared to men that only used the sauna one time per week. Men that used the sauna 4-7 times per week had a 66% lower risk of dementia and a 65% lower risk of Alzheimer’s disease compared to men that used the sauna once a week.
    • The other molecular pathway of interest that may help to explain some of what’s going on with this association between longevity and sauna use is a pathway known as the FOXO3 pathway.There is some evidence that part of the natural cellular stress response, when confronted with heat, is an activation of this pathway. FOXO3 is one of the big aging genes involved in longevity: humans with a polymorphism that makes more FOXO3 have up to a 2.7-fold increased chance of living to be a centenarian and in mice, having more of their homologous version of this same gene can extend their lifespan by up to 30 percent! As a pattern of aging, our FOXO3 activation trends downward… decreasing in expression with age, FOXO3 is a master regulator is involved in: autophagy, DNA repair, metabolism, endogenous antioxidant production, stem cell function and immune function.

How much sauna is enough?

  • For the minimal benefits of lower cardiovascular disease mortality, lower all-cause mortality, and lower Alzheimer’s disease risk: 
    • 20 minutes at 174º F (or 79º C) 2-3 times per week.
    • 4-7 times a week, had an even more robust effect. 
  • The minimum effective dose for endurance appeared to be 30 minutes in a 194 fahrenheit (90C) sauna twice a week… a dose which, by the way, produced a maximum heart rate of 140 beats per minute.
  • For endocrine effects in the area of growth hormone multiple studies report ranges of 20-30 minutes and around 176°F (or 80°C ) in the neighborhood of 2-3 times a week.
  • Molecular evidence for heat-shock protein induction seems to indicate that healthy young men and women sitting in a 163°F (73 C) sauna for 30 minutes are able to increase their heat shock protein levels including, hsp72, by 49% and that the elevation in heat shock protein levels persist for 48 hours after the initial heat stress, suggesting 2-3 times per week is a good moderate frequency to hit a threshold for some sustained effects.

Areas where the science may be promising but maybe not quite as robust or otherwise confer itself well to talking about a minimum effective dose, including:

  • The possibility that that sauna use could play a role in mood and attention by increasing norepinephrine and affecting our sensitivity to and production of beta-endorphin, giving us a sort of runner’s high… the potential of which was something that initially appealed to me when experimenting with my own personal sauna use.
  • The possibility that sauna use may reduce muscle atrophy and then muscle regrowth — an effect which, while very interesting, is mostly shown in animal studies that might be hard to try to then apply back to humans.

What about Hot – then Cold?

Both heat stress from the sauna and even cold stress are both able to activate heat shock proteins. This is because heat shock proteins respond to cellular stress in general and not exclusively heat stress. Heat, as a cellular stress, does cause a more robust activation than cold though. One of the main reasons to expose yourself to the cold are the effects it seems to have on the brain, mood and possibly attention. One of the most likely candidates for eliciting an effect is norepinephrine, which is also the catecholamine that is actually responsible for triggering the browning of fat, making our fat more metabolically active. In fact, in terms of pathways or physiological responses to cold, the release of norepinephrine into the bloodstream, as well as in the locus coeruleus region of the brain, is one of the more profound. Guess what else increases norepinephrine release? Heat as from sauna use. So this is a second way in which both hot and cold, instead of having opposing effects where one cancels out the other, at the molecular level they are nudging some of the same pathways in the same direction. But, to elicit these overlapping stress responses, you actually have to get cold enough for that to happen. Otherwise, you’re actually just taking some of the heat burden you created on your own body and removing it. In the case of a 30-second cold shower that isn’t sufficient to even trigger momentary discomfort, it is probably not adding stress but in fact simply removing it. Studies have shown that people that immersed themselves in cold water at 40°F (4.4°C) for 20 seconds increased their norepinephrine 2 to 3-fold (200 to 300%) and this release of norepinephrine didn’t seem to be reduced with habituation to cold. Long durations of cold water exposure under more moderate temperature have a more potent effect on norepinephrine release. People that spent 1 hour in 57°F (14°C) water increased norepinephrine in their bloodstreams by 530% over baseline.

How regular hyperthermic conditioning and hypothermic stress relate to muscle hypertrophy and strength training?

There are a couple of main mechanisms that hyperthermic conditioning through using the sauna may plausibly affect muscle hypertrophy. First, is through the robust activation of heat shock proteins. I mentioned earlier how heat shock proteins play a role in preventing neurodegenerative diseases such as Alzheimer’s disease by helping proteins maintain their proper 3-dimensional structure. Not only does this have a role in preventing the aggregation of proteins but it may also plays a role in muscle hypertrophy.

Muscle hypertrophy is ultimately the delta between protein degradation and new protein synthesis. When we train for muscle hypertrophy we often put a lot of thought into how to increase muscle protein synthesis… but if we reduce protein degradation, which is an effect heat shock proteins have, we are still increasing our net protein synthesis by increasing the difference between the amount of new synthesis of muscle protein versus the amount of degradation that is happening. This type of effect has been shown in rats where it was shown that a 30-minute heat treatment at a temperature of 106°F (41°C ) given every 48 hours over a 7 day period caused a sustained increase in heat shock proteins during that time frame, but more importantly, this actually correlated with a whopping 30% more muscle regrowth than a control group during the seven days after immobilization.

The other way that hyperthermic conditioning through using the sauna could plausibly affect hypertrophy is by robustly increasing growth hormone. For example, two 20-minute sauna sessions at 176°F (80°C) separated by a 30-minute cooling period elevated growth hormone levels two-fold over baseline. An even more robust effect was found with men using higher sauna temperatures. Two 15-minute sauna sessions at 212°F (100°C) separated by a 30-minute cooling period resulted in a five-fold increase in growth hormone. The boost in growth hormone levels is transient and only lasts a couple of hours.  Many of the effects of growth hormone are mediated through another hormone known as IGF-1 or insulin-like growth factor-1. IGF-1 activates another pathway in skeletal muscle known as mTOR, which is responsible for new protein synthesis. Muscle cells require amino acids for both growth and repair so if we can also plausibly activate mTOR we’re now sort of completing the circle. With heat shock protein induction we reduce protein degradation and through these endocrine effects, actually increasing protein synthesis; by increasing net protein synthesis, we effectively increase hypertrophy.

In fact, if you sort of reverse engineer the habits of bodybuilders: IGF-1 is actually one of the major pathways most robustly activated by dietary protein intake. So the next time you’re shoveling down protein powder or essential amino acids like leucine… you can be aware that part of what you are doing in the first place is robustly activating the production and release of IGF-1 and thus mTOR. Protein (and specifically essential amino acids) are the major dietary regulators of IGF-1. IGF-1 plays a very important role in muscle growth and repair.

When we train, as a result of the mechanical work being done we produce metabolic byproducts like reactive oxygen species and we also activate inflammatory cytokines. This is actually necessary to activate genetic pathways that contribute to creating more mitochondria (mitochondrial biogenesis as we talked about) and also plays a role in muscle hypertrophy. In fact, it is inflammation that recruits immune cells such as macrophages to skeletal muscle in order to produce IGF-1 that helps induce acute muscle repair. There has been some experimental evidence that indicates that these specific immune cells are also likely involved in satellite cell migration, which is a type of muscle stem cell that serve as precursors to actual muscle cells and for which the raw number of are actually associated very closely with the amount of actual hypertrophy that occurs as a result of strength training.

As we can see, inflammation seems to play a pretty important role in the benefits of actual training. And this inflammation, as measured by an inflammatory cytokine known as IL-6, actually peaks during training and also right after but then falls by 50% of its initial peak after the first hour. So, in a way, if you’re going to try to pick a time to increase growth hormone or IGF-1 activity, it makes sense to probably do so in close proximity to when it’s actually peaking. In my mind, I interpret this to be pretty much immediately on the tail end of my work out. But this peak of inflammation potentiating IGF-1 synthesis that then goes on to play a role in hypertrophy may become especially relevant if we talk about the mixed research surrounding cold stress, such as ice baths or cryotherapy, especially when used in conjunction with working out.

Whereas the sauna seems to be just fine and maybe even beneficial to do immediately after exercise, cold water immersion and possibly other modalities of cold exposure are a bit more nuanced in the context of strength conditioning. Specifically, studies have shown mixed results when paired with strength training. For example, one 2015 study in the Journal of Physiology showed that a 10-minute cold-water immersion immediately following heavy leg training dramatically decreased hypertrophy by almost 2/3rds at 10-weeks follow-up. The active cold treatment group also had a reduction in muscle strength and showed smaller increases in type II muscle fibers which are required for very short-duration, high-intensity bursts of power and all of this coincided with a reduction in biomarkers that are usually associated with hypertrophy, including the activation of satellite cells. 

But maybe it shouldn’t be too surprising. Let’s unpack this anti-hypertrophy effect of cold a little bit. One of the reasons ice baths became popular in professional sports, for example, is because cold exposure blunts inflammation and, specifically, it’s been shown to dramatically decrease the production of what are known as E2 series prostaglandins, which are one of the factors that have specifically been shown to induce the synthesis of IGF-1 by macrophages, that growth factor mentioned earlier because it’s important for hypertrophy. In addition to this, cold exposure also causes vasoconstriction which may also acutely prevent immune cells from migrating to places like muscle tissue. Knowing how to reduce inflammation when needed is good, but only if we account for the various downstream effects that this may have.

This is not the only study (although it is the best one) that has shown that cold water immersion done immediately after strength training may blunt some hypertrophy. There are others but again all of those studies used cold exposure sometime immediately after strength training. So that leaves us with a few open questions, but the most important one is this: would we still have seen the blunted or reduced hypertrophy effects if cold-water immersion was done at literally any point other than immediately after strength training? I don’t think that, based on the current literature, that we can state this 100% certainty at this stage, but if we take into account this potentially inflammatory-mediated anabolic window that seems to peak especially in the first hour post-exercise, then it might help explain some of the mixed results we see surrounding the use of cold stress with various forms of strength training. Specifically, one 2013 study from the Scandinavian Journal of Medicine & Science in Sports showed the almost exact opposite effect — this study showed that whole body cryotherapy for a couple minutes done 1 hour after squat jumps and leg curls was actually associated with performance enhancements which included improvements in power at the start of the squat jump, and squat jump work-up and improved pain measures up to 72 hours after the cold treatment.

This isn’t the only study showing an enhancement in performance from cold either. We see in a study published in PloS one in 2011 that Elite runners that engaged in whole-body cryotherapy 1 hour, 24 hours, or 48 hours after doing some hill sprinting ultimately had a 20% increase in speed and power up to two days later. What’s interesting about the cold is that it may also be conducive to enhancing endurance-related activities in particular. Like fat, whereby cold can increase the number of mitochondria in white adipose tissue in order to transdifferentiate it into brown fat, a form of fat that is metabolically active, protective against obesity, and naturally declines as we age. Muscle also experiences an increase in mitochondria as a consequence of cold exposure. These mitochondria are the energy-producing machinery of our muscle cells. The density or number of them on a per cell basis affects our aerobic capacity. Mitochondria are what give us the ability to use oxygen in order to produce cellular energy, and if we have more of them, it can be said we may be more adapted to aerobic activity. Mitochondria are what give us the ability to use oxygen in order to produce cellular energy, and if we have more of them, it can be said we may be more adapted to aerobic activity.


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