Harnessing Heat: The Enduring Benefits of Sauna Use for Athletes
Dr. Rhonda Patrick on how deliberate heat acclimation reshapes endurance, muscle repair, and brain chemistry — delivering the gains of growth hormone therapy without the longevity cost.
Video·FoundMyFitness·14 min read·June 2026
Dr. Rhonda Patrick on how deliberate heat exposure reshapes endurance, muscle repair, and brain chemistry — without the risks of hormone therapy.
The Case for Hyperthermic Conditioning
Growth hormone and IGF-1 sit at the center of one of performance science's sharpest tensions. As a downstream mediator of growth hormone, IGF-1 activity supports the biological markers athletes value most: reduced body fat, increased lean muscle, sharpened verbal memory, accelerated neurogenesis, and faster tissue repair. These are not peripheral effects — they represent the core physiology of youth, recovery, and peak performance. Yet organisms engineered to sustain elevated growth hormone or IGF-1 — mice, worms, flies — show substantially shortened lifespans. The same signals that build the body can, at chronically elevated levels, accelerate its decline.
Hyperthermic conditioning navigates this trade-off with uncommon precision. By systematically acclimating the body to heat through deliberate sauna use — calibrated by temperature, duration, and frequency — you can achieve many of the same physiological adaptations associated with IGF-1 activity, without triggering the supra-physiological growth hormone levels that accompany exogenous therapy. The body treats heat as it treats exercise: as a stressor to adapt to, a demand to grow stronger from. Each session is a signal; the accumulated response is adaptation.
The adaptations span three distinct domains. Endurance performance improves as heat acclimation reshapes cardiovascular efficiency, nutrient delivery, and the body's thermoregulatory capacity under sustained physical load. Muscle hypertrophy advances through three separate biological pathways, each addressing the degradation side of the protein synthesis equation and tipping the balance toward net growth. In the brain and neuroendocrine system, heat drives changes that sharpen focus and alertness, stimulate new neuron growth, and amplify the post-workout high beyond what exercise alone can produce.
This reframes the sauna as something more demanding and more rewarding than passive recovery. Deliberate heat exposure induces physiological stress in order to build physiological tolerance — that is, by definition, training. Athletes who approach each sauna session with the same intentionality they apply to progressive overload or tempo runs will find that the heat responds accordingly, producing adaptations that extend and deepen the work already done. The sanctuary, it turns out, is also a laboratory.
The research behind these claims has accumulated across exercise physiology, endocrinology, and neuroscience — drawing on studies in both humans and animal models that isolate heat as the active variable. What that body of evidence reveals is a tool with quantifiable returns spanning performance, recovery, and longevity. Understanding the mechanisms makes it possible to deploy that tool with precision and to calibrate protocols that compound over time.
Dr Ronda Patrick here in my last video and accompanying article I discussed growth hormone and igf-1 and their performance longevity trade-off on the one hand as a downstream mediator of growth hormone igf-1 has many positive effects associated with youth such as decreasing fat while increasing lean muscle mass increasing verbal memory and increasing neurogenesis the growth of new brain cells and also promoting muscle repair on the other hand mice worms and flies that are genetically engineer to have high levels of growth hormone or igf-1 have substantially shortened lifespans hence the trade-off heat acclamation through sauna use a term that I call hypothermic conditioning can help achieve and give you many of those positive effects associated with igf-1 without the risk of high levels of growth hormone or Supra physiological levels of growth hormone that's associated with growth hormone therapy today I'm going to discuss how acclimating your body to
heat through using something like the sauna either in conjunction with or independent of exercise can induce physiological adaptations that can help improve your endurance performance and the acquisition of muscle mass in addition I'm going to discuss how heat acclimation actually has very interesting and positive effects on the hypothalamus and neuroendocrine system many of these impacting brain function including neurogenesis lastly I will discuss how heat acclamation or modulating your core body temperature may also be responsible for the term known as the runner's high so let's begin with the endurance enhancements first heat acclamation increases the blood flow to your skeletal muscles this increases glucose esterified fatty acids and oxygen to your skeletal muscles often times during
endurance training your skeletal muscles will deplete these nutrients and then they have to rely on local glycogen stores anecdotally endurance athletes often talk about hitting a wall while this in biological terms is referring to when your muscles have depleted local glycogen stores in fact it's been shown that heat acclamation reduces the need to to rely on glycogen stores between 40 and 50% as compared to not being heat acclimated second heat acclamation increases blood flow to the heart this lowers cardiovascular strain and lowers the heart rate for the same given exercise workload these things allow physical activity to be maintained for a longer period of time as compared to not being heat acclimated third is heat acclimation increases blood flow to the skin and it activates the sympathetic nervous system which allows sweating to occur at a lower core body temperature and to be maintained for a longer period
therefore lowering your core body temperature it also releases nor epinephrine which is a vasodilator among other things and allows for heat to be dissipated more efficent efficiently also lowering the core body temperature so let's take a step back from these nuts and bolts and talk about what kind of endurance gains you can expect from heat acclamation through sauna use in one study male Runners engaged in a 30 minute sauna session two times a week after their workout these Runners were able to increase their running until exhaustion by 32% and they experienced an accompanied 7% increase in plasma volume and 3.55% increase in red blood cell count it's thought that the increase in red blood cell count was due to a compensatory mechanism for the increased plasma volume and possibly through arotin heat acclamation through SAA use can also have positive effects on muscle hypertrophy tropy that is gaining muscle
mass muscle hypertrophy mostly relies on the increasing the size of muscle cells which depends on increasing protein synthesis exercise is a well-known inducer of muscle hypertrophy because it increases net protein synthesis but unfortunately it also has to combat the effects of oxidative stress which increases protein degradation at the same time so anything that can combat oxidative stress during exercise will result in a net increase in protein synthesis and thus muscle hypertrophy there are three ways that being heat acclimated can increase muscle hypertrophy first is through the induction of heat chock proteins second is by boosting growth hormone levels and third is by improving insulin sensitivity heat shock proteins as their name implies are induced by heat this robust induction of heat chog proteins upon Heat exposure is a prime example of
hormesis heat shock proteins are able to repair damaged proteins and prevent protein oxidation by Scavenging free radicals and by increasing endogenous antioxidants in our body such as glutathione and this is how they are able to cause a net increase in protein synthesis acclimating your body to heat can also result in higher basil expression of heat shock proteins as well as a more robust induction during later elevations in Core Body temperatur such as during physical exercise in one study in rats hypothermic conditioning resulted in a robust induction of heat chock proteins and this correlated with 30% more muscle regrowth compared to controls after 7 Days of immobilization the second way heat acclimation affects muscle hypertrophy is through the release of growth hormone the anabolic effects of growth hormone are well known for example Le growth
hormone Administration to endurance athletes for 4 weeks resulted in 50% less protein oxidation and degradation thereby increasing muscle hypertrophy but what's not well known is that the sauna also affects growth hormone levels these effects depend on the temperature time spent and the frequency of sauna use for example two 20 minute sauna sessions a day at 80° C can result in a two-fold increase in growth hormone levels over Baseline but perhaps what's more surprising is the profound effects that frequency of SAA use can have on growth hormone levels and this really highlights the physiological adaptations that occur as a consequence to hypothermically conditioning your body to heat two 1H hour a day sauna sessions at 80° C for 7 days in a row resulted in a 16-fold increase in growth hormone levels over Baseline in men that's pretty huge
the third way in which heat acclamation can promote muscle growth is by improving insulin sensitivity insulin is anabolic because it decreases protein degradation much like heat shock proteins and growth hormone whole body hypothermia has been shown to reduce insulin resistance and improve insulin sensitivity and an OB diabetic Mouse model what's also interesting is that heat stress which is known to boost growth hormone levels in humans has been shown in flies and worms to cause about a 15% increase in lifespan now this is countered to what you might expect if you watched my last video on the performance longevity tradeoff the reason for this is that heat stress induces hormesis and that causes the increase in expression in genes and protein proteins such as heat chock
proteins that are known to improve longevity intermittent heat exposure and heat acclamation also have positive benefits on the brain these positive benefits include increased neurogenesis improved learning in memory and improved Focus SAA induced hypothermia also has a profound effect on noro epinephrine and prolactin levels in one study individuals that stayed in the sauna until exhaustion had a 310% increase in norepinephrine and a 10-fold increase in prolactin levels norepinephrine helps with focus and attention and prolactin is important for myelin growth milin increases the efficiency of the electrical activity in your brain and is also important for repairing nerve cell damage in addition to increasing norepinephrine heat acclamation also increases the biological capacity to store neuro epinephrine for later release this is very relevant for disorders such as ADHD which is is often treated with nor epinephine reuptake
Inhibitors and is associated with decreased nor epinephine release during exercise heat stress also increases neurogenesis hypothermia in conjunction with exercise increases the expression of brain derived neurotrophic Factor bdnf even more so than exercise alone bdnf is often referred to as a Miracle Grow for brain cells because it increases the grow grow of new brain cells and it promotes the survival of already existing neurons bdnf also increases neuronal plasticity which is important to learn new information as well as to remember and retain that new information BNF has also been shown to decrease depression and anxiety associated with early life stressful events and if that weren't enough bdnf can also be released from your muscle cells where it promotes muscle repair and the growth of new muscle Tiss tissue
all I can say is wow a couple of other interesting facts about physiological effects of heat stress ever wonder what's responsible for the runner's high or the post exercise high in general you may think it's due to the release of endorphins but that's not the whole story endorphins also known as beta endorphins are part of the body's natural mu opioid painkiller system this is the same system that potent narcotics like morphine interact with what you may not be familiar is the counterpart to this the Kappa opioid system dorphin is responsible for that feeling of dysphoria it is the opposite of endorphin the discomfort experienced from intense exercise heat stress or even eating spicy foods is due to the release of that dysphoric opioid dorphin it is the release of dorphin that caus causes your mu opioid receptors to
become sensitized to that feel-good opioid endorphin hypothermia from sauna use increases dorphin levels and subsequently endorphin levels even more than exercise alone did you retain all that awesomeness I just threw at you okay let's have a quick recap heat acclamation through Sona use a term I call hypothermic conditioning has been shown to improve endurance by increasing nutrient delivery to your muscles and thereby reducing the need for glycogen stores by improving cardiovascular mechanisms and reducing heart rate and also by improving therm regulatory mechanisms and lowering core body temperature it's been shown to improve muscle hypertrophy by the by preventing protein degradation and thereby causing a net increase in protein synthesis from the following three mechanisms one by inducing the expression of heat chock proteins which also are induced from a
hormetic response that has been shown to improve longevity in lower organisms secondly by increasing the release of growth hormone and thirdly by improving insulin sensitivity hypmic conditioning through SAA use also has important positive effects on the brain it increases the release and the storage of norepinephrine which is important for focus and attention it increases prolactin which helps your brain function faster through myelination which is Al important for repairing uh damaged nerve cells in addition increases bdnf which increases the growth of new brain cells it is important for learning in memory and also helps decrease depression and anxiety that's associated with early stressful events lastly it also increases the expression of dorphin which sensitizes your body to the Feelgood endorphin I believe that hypmic conditioning in general is worth a closer look as a tool in the tool bit of athletes Beyond its more traditional
role as a means of relaxation because hypothermic conditioning works by inducing stress in order to build stress tolerance it should definitely be used with some level of caution and Common Sense particularly with regards to your own unique body chemistry here's one more thing for you CrossFit people out there heat stress has been shown to increase the expression of heem oxygenase one which as it turns out is also known as heat shock protein 32 and has been shown to protect against the toxic effects of rabdomiolisis and rodents I'm Dr Ronda Patrick and I'll catch you next time
Transcript auto-generated by YouTube. Verbatim — duplicates intentionally preserved.
Heat Acclimation and Endurance Performance
Endurance performance depends on how efficiently the body delivers and uses resources under load — and heat acclimation reshapes that efficiency across three distinct circulatory mechanisms. The first is increased blood flow to skeletal muscles. Greater circulation means more glucose, esterified fatty acids, and oxygen reach working tissue continuously, reducing the rate at which muscles must draw on local glycogen stores. Heat-acclimated athletes delay the onset of glycogen depletion by 40 to 50 percent compared to their non-acclimated counterparts — a physiological advantage that translates directly into sustained performance.
The second mechanism involves the heart itself. Heat acclimation increases blood flow to the cardiac muscle, which lowers cardiovascular strain at any given exercise workload. The heart beats less for the same output. For endurance athletes, that efficiency margin is the difference between fading in the final miles and finishing strong — because sustained cardiovascular output becomes less costly and, therefore, more available.
The third mechanism is thermoregulatory. Heat acclimation increases blood flow to the skin and activates the sympathetic nervous system in ways that allow sweating to begin at a lower core body temperature. Norepinephrine — released as part of this response — acts as a vasodilator, helping the body dissipate heat more efficiently and keeping core temperature from rising to performance-limiting levels. The result is enhanced clarity and endurance under thermal stress; the body runs cooler, and keeps running longer.
These three mechanisms work in concert, and their cumulative effect on endurance is measurable. In a controlled study, male runners completed 30-minute sauna sessions twice per week following their regular workouts. The outcome was notable: run time to exhaustion increased by 32 percent, accompanied by a 7 percent rise in plasma volume and a 3.5 percent increase in red blood cell count. The increase in red blood cells is understood as a compensatory response to expanded plasma volume — the body producing more oxygen-carrying capacity to match its enlarged circulatory system.
endurance athletes often talk about hitting a wall while this in biological terms is referring to when your muscles have depleted local glycogen stores
Plasma volume expansion and red blood cell growth represent two of the same adaptations that altitude training is designed to produce — yet here they emerged from seated, post-workout heat exposure. The sauna becomes a circulatory training tool, working the cardiovascular system through a different kind of demand and arriving at the same enhanced oxygen economy. Recovery and performance, in this protocol, are not separate activities. They are the same session.
What connects these mechanisms is the body's fundamental capacity to adapt when challenged with the right stimulus at the right intensity. Heat acclimation conditions the cardiovascular system to operate more efficiently under thermal and physical stress, raising the ceiling for what that system can sustain. Each sauna session is, in effect, a rehearsal — the body practicing the circulatory coordination it will need when the real demands arrive, and emerging from that rehearsal a little more capable than before.
Three Pathways to Muscle Growth
Muscle growth depends on net protein synthesis — the difference between how much protein the body builds and how much it breaks down. Exercise is the most familiar stimulus for growth, but it comes with a complication: intense physical work simultaneously increases oxidative stress, which accelerates protein degradation. The net gain depends on how well the body manages that oxidative burden. Heat acclimation addresses this problem through three distinct biological pathways, each one reducing degradation or enhancing synthesis, collectively tilting the balance toward growth.
The first pathway runs through heat shock proteins. These molecular chaperones are induced by heat in what is a prime example of hormesis — a beneficial adaptation triggered by controlled stress that drives the body toward greater resilience and recovery capacity. Heat shock proteins repair damaged proteins and prevent further oxidation by scavenging free radicals and elevating the body's production of endogenous antioxidants, including glutathione. In a study using rats, hyperthermic conditioning produced robust heat shock protein induction that correlated with 30 percent more muscle regrowth after seven days of immobilization, compared to controls. Protection against degradation — and the recovery it enables — begins at the molecular level.
Regular heat exposure also raises the basal expression of heat shock proteins, meaning the body holds a larger defensive reserve. When core temperature rises again — during the next training session, the next physical demand — the response is faster and more robust, delivering greater protection for muscle protein and accelerating recovery between efforts. The body becomes, over time, better at protecting itself. That upregulated baseline is one of the quieter but more durable benefits of consistent hyperthermic conditioning.
The second pathway involves growth hormone. Two 20-minute sauna sessions per day at 80 degrees Celsius produce a two-fold increase in growth hormone levels over baseline. But the effect of frequency is what makes this finding particularly instructive: two one-hour sessions per day at the same temperature, maintained for seven consecutive days, produces a 16-fold increase in growth hormone levels over baseline. The degree of adaptation scales with the commitment to the protocol.
Growth hormone is anabolic in a highly practical sense — it reduces protein oxidation and degradation, directly protecting the muscle tissue that training builds. Research on endurance athletes receiving growth hormone administration demonstrated 50 percent less protein oxidation and degradation over a four-week period. The sauna drives growth hormone elevation through the body's own regulatory systems, achieving a meaningful version of that effect without exogenous intervention and without the lifespan trade-off that supra-physiological levels carry.
The third pathway is insulin sensitivity. Insulin is inherently anabolic: it slows protein breakdown, keeping the tissue that synthesis builds intact for longer. Whole-body heat exposure reduces insulin resistance and improves insulin sensitivity, creating a more favorable anabolic environment across the entire system. Each unit of insulin does more work; the net metabolic balance tips further toward growth and recovery. And in a parallel finding from lower organisms, heat-stress-driven expression of heat shock proteins has been linked to approximately 15 percent lifespan extension — a reminder that the adaptations heat induces are not only about performance, but about the enduring health of the systems doing the work.
The Brain, the High, and the Bigger Picture
The neurological effects of heat acclimation begin with norepinephrine — and they begin emphatically. Studies in which participants remained in the sauna until exhaustion recorded a 310 percent increase in norepinephrine levels. Norepinephrine is the neurotransmitter most closely associated with focus and attention; its elevation sharpens cognitive clarity and sustains directed effort in ways that carry well beyond the sauna session itself. Heat does not merely relax the mind — it primes it.
What makes this particularly relevant for athletes is not just the acute spike, but the adaptive response. Regular heat exposure increases the biological capacity to store norepinephrine for later release, building a deeper reservoir of attentional and cognitive resource — a measurable gain in focus and alertness that compounds with practice. This has direct implications for disorders such as ADHD, which is characterized by reduced norepinephrine release during exercise and typically treated with norepinephrine reuptake inhibitors. Hyperthermic conditioning builds the infrastructure for sustained mental clarity from the inside, through natural physiological adaptation.
The sauna also produces a 10-fold increase in prolactin. Prolactin drives the growth of myelin — the insulating sheath around nerve fibers that increases the speed and efficiency of electrical signaling in the brain, translating directly into sharper mental performance and clearer thinking under pressure. Greater myelination means faster neural processing; the mind keeps pace with the demands placed on it. Prolactin also plays a role in repairing damaged nerve cells, adding a neurological recovery dimension to heat exposure that extends its benefits well beyond muscle and cardiovascular adaptation.
BDNF — brain-derived neurotrophic factor — is amplified by heat stress beyond what exercise alone produces. BDNF stimulates neurogenesis, promotes the survival of existing neurons, and increases neuronal plasticity, which underpins the capacity to learn and retain new information. It also reduces depression and anxiety associated with early-life stress. The same session that builds cardiovascular efficiency and protects muscle protein is simultaneously doing maintenance and renovation on the neural architecture supporting everything the athlete does.
The post-sauna high is its own mechanism — and a more sophisticated one than it first appears. Intense heat produces discomfort, and that discomfort is generated by the release of dynorphin, which activates the kappa opioid system. Dynorphin sensitizes the mu-opioid receptors — the same receptors activated by endorphins — and when endorphins arrive in response, they find receptors primed to respond more powerfully. The result is an elevated sense of calm and wellbeing that surpasses what exercise alone delivers; the discomfort and the reward are two sides of the same protocol.
Hyperthermic conditioning belongs in a serious athlete's protocol — not as a luxury or a passive wind-down, but as a deliberate tool for building the physiological and neurological capacity that sustains long-term performance. The mechanisms are established; the adaptations are measurable; the returns compound with consistent practice. Approach each session with precision — calibrate temperature, duration, and frequency with the same care applied to any other training variable — and the heat will do its part. Every body is different, and awareness of individual chemistry is the steady companion to any protocol worth keeping.
