6 ms·

Sauna effect on heart rate

448 points by kyriakosel 6mo ago

kyriakosel 6mo ago
Author here. Methodology upfront because I'd ask the same things: Data: daily records from wearable users who logged sauna sessions via connected apps. Within-person design — each user is their own control, comparing their own sauna-day nights against their own non-sauna-day nights. No cross-user comparisons. Stats: paired t-tests, FDR-corrected p < 0.05, Cohen's d > 0.2 threshold for "meaningful effect." Anything below d=0.2 we don't report as a finding. What we measured: minimum nighttime HR, max and average HR, HRV, activity minutes and distance, menstrual cycle phase (for female subset). What we found: - On sauna days, minimum nighttime HR drops ~3 bpm (~5%) vs. the same user's non-sauna days. - Effect survives controlling for activity level. It's not "sauna users just exercised more that day." - Strongest hypothesis: elevated parasympathetic tone from the post-sauna cooling phase carries into sleep. Consistent with heat-stress physiology literature. - Sex difference: for women, the nighttime HR effect only crosses the d > 0.2 threshold during the luteal phase. No meaningful effect during the follicular phase. We didn't expect this; worth replicating. What we can't control for: - Sauna type (dry / infrared / steam), duration, temperature. Not captured. - Dose-response. We don't know session length per user. - Timing of sauna relative to sleep. - Reverse causation: people may sauna on days they already feel recovered. - Selection: wearable users who bother logging sauna are a health-conscious cohort. What surprised us: the effect is larger than what we see for comparable-intensity exercise days. If you treat nighttime HR as a parasympathetic recovery signal, sauna beats a moderate workout on the same user. Not what I'd have predicted.
- itsthecourier 6mo ago
  how does this reduction in heartbeat at night affect the body?
- croemer 6mo ago
  Why didn't you put the methodology in the post? Also, which devices were used to record? How do you know people went to sauna?
- bluGill 6mo ago
  The most important thing you didn't measure: does this affect long term health in the same way exercise it known to. That is can I put a TV in my sauna and watch that for an hour every day instead of getting out and exercising - yet get the same better long term health outcomes? My current guess is no. That is this improves a marker for good health without improving health. However this is a guess by someone who isn't in the medical field and so could be wrong.
  - testing22321 6mo ago
    I don’t think the TV in the sauna will have long term health outcomes.
    - Filligree 6mo ago
      It will certainly affect the health of the TV.
  - kyriakosel 6mo ago
    Agreed - one is muscular/metabolic demand, the other (sauna) is thermoregulation. Agreed on the long-term effect too: doing a study on long term health is a completely different story
  - nsbk 6mo ago
    I recently listened to a podcast about the benefits of sauna or deliberate heat exposure and the gist is that if you get your core temperature at about 39 degrees celsius your cardiovascular system is working comparably hard to light exercise. My take is that your heart and lungs are working out, even if your body is not. Do you get the same benefits as going for a run or bike ride for a comparable amount of time? no, since your limbs don't get fit, but your heart and lungs do.
    - mminer237 6mo ago
      Edit: I posted this accidentally when editing without noticing. Hypertrophy isn't necessarily a bad thing. I thought I was discarding the comment cuz I realized I was out of my depth. whoops Please ignore my comment, though I will leave it to make the below comments less confusing. Original: You don't want to "work out" your heart though. Cardiac hypertrophy is a bad thing. The benefit of exercise is that your muscles become more oxygen-efficient. Your heart endures some stress now, so that it can work less in the future.
- gamerslexus 6mo ago
  It would be very interesting if lowering night heart rate only happens with certain sauna type. > What we can't control for: - Sauna type (dry / infrared / steam), duration, temperature. Not captured Could probably capture humidity/duration/temperature using a sensor in wearable device...
  - kyriakosel 6mo ago
    we agree - but thats not that simple :)
    - methyl 6mo ago
      > who logged sauna sessions via connected apps It seems you ask participants to log if they went to sauna. Out of curiosity, why is it not simple to also ask for a type?
      - kyriakosel 6mo ago
        i was mostly refering to humidity/duration/temperature given that most devices do not report back these values
        austinthetaco 6mo ago
        I'm equally confused as the other person above. Why not just ask participants to report what type of sauna they used? Sure humidity/duration/temp would be awesome to have, but at the very minimum knowing if a dry sauna would get the same results as a traditional steam sauna.
        gamerslexus 6mo ago
        What if they jumped between saunas? And with self-reporting, the more you ask I guess the less precise the result... Sensors, however...
        PaulDavisThe1st 6mo ago
- lccerina 6mo ago
  If this was a peer-reviewed paper, it won't pass. - Is the wearable accurate enough to be sure that 3bpm is not a measurement fluke? - Why did you use the minimum heart rate value (which could be a measurement glitch) and did not compare a percentile (e.g., 2.5th lowest percentile)? - Were all assumptions for paired t-testing valid? How did you account for likely temporal correlations in the data (e.g., sauna could have an effect also on a night 2 days after it, same for exercise)? - How can you define a "comparable-intensity exercise day" if you don't know the characteristics of the sauna?
  - joelthelion 6mo ago
    > Is the wearable accurate enough to be sure that 3bpm is not a measurement fluke If the statistical tests show significance (and are valid), the answer to this question is yes. If you have enough data you can make strong conclusions even witwith imperfect hardware.
    - gjulianm 6mo ago
      Unless the effect they're measuring is that the wearable measures differently in sauna days.
    - ranguna 6mo ago
      Strong conclusion that the hardware is precisely imperfect?
    - lccerina 6mo ago
      Not at all, if you have a lot of data coming from imperfect hardware (which can mean both a fixed bias and unknown variance), and you don't know the variance for plenty of practical reasons, you are left with a result that is statistically significant, but wrong
- jtanderson 6mo ago
  Just as a discussion point: how do you think these effects would translate (if at all) to regularly practicing hot yoga, say around 100-105F? Intuitively, it would combine the effort + recovery, but probably not enough time elapsed in the same session for the sweat benefit during muscle repair?
- Glemllksdf 6mo ago
  Or the sauna is a relaxing thing like a happy place and that reduces heart rate?
- gjulianm 6mo ago
  > Effect survives controlling for activity level. How did you control for activity level? Do you have similar BPM plots for the different situations (sauna+exercise, sauna+no exercise, no sauna + exercise, no sauna + no exercise) for a visual representation? > minimum nighttime HR drops ~3 bpm (~5%) What wearables were used? These devices don't usually have enough precision to reliably detect ~3bpm changes. Also, the measurements are sensitive to skin, blood flow changes and temperature. How do you know the difference doesn't come from different sensor behavior after sauna?
  - jampekka 6mo ago
    > What wearables were used? These devices don't usually have enough precision to reliably detect ~3bpm changes. For large sample averages this doesn't really matter.
    - gjulianm 6mo ago
      It does, specially if the error bars from multiple measurements show higher precision than what would be expected.
      - jampekka 6mo ago
        I don't understand what you mean by that. Precision (inverse of variance) of estimate of mean increases directly proportional to number of samples (given some assumptions that very likely hold here). If you have measurement standard deviation of say 10 bpm, with 100 measurements you have mean estimate standard deviation of 10/sqrt(100) = 1 bpm.
        gjulianm 6mo ago
        > of estimate of mean But you can't really assume that the estimate of the mean represents the real value. For example, if the sensor is equally likely to show 80 or 81 BPM when the real heartrate is 80.7, the mean estimator will be biased. > with 100 measurements Also, wearables aren't taking 100 measurements of the BPM at a given point in time. I think the highest frequency they usually have is 1 second measurement interval. So they don't really have a lot of measurements for each point in time. > mean estimate standard deviation That's the standard deviation of the mean of the values. Doesn't imply that the standard deviation of the values themselves will go to zero. > I don't understand what you mean by that. That as a rule of thumb, you should not assume that repeating measurements will give you more precision than what the tool can offer. E.g., trying to measure down to milimeters with a ruler that has only 1cm marks will not really work well.
- al_borland 6mo ago
  How would this play out over time? Will sauna see a 3bpm drop below baseline on days it’s used, while keeping the same baseline? Exercise, over time, should lower the baseline (to a point). I’d think this would have the more desirable long term benefits. One can do both, of course, but when people see headlines like this they often jump to the conclusion that sauna can replace exercise, because that’s what they want to believe.
  - verst 6mo ago
    Due to lots of long distance running my rest heart rate is below 40. I am highly skeptical I would experience a 3bpm lower heart rate after sauna. Maybe this benefit applies after infrequent activity or less intense activity only.
- jampekka 6mo ago
  I'd like to see a bit more detailed methods. - How was the controlling for the other factors done? A linear model? - What were the sauna vs non-sauna baseline HRs in fig 1? Could you plot raw averages? - Was the min HR explicitly computed during the night (in Fig 2), or was it assumed min HR occurs during the night? - Reporting only significant results is not prudent even with multiple comparisons corrections, please report all tests made
- lazyant 6mo ago
  Would a hot tub session (say at 100 - 105 F) be comparable or yield similar results?
  - pstuart 6mo ago
    Dr. Rhonda Patrick has been beating the drum for saunas for a long time, and she's reported that a hot tub can be equivalent or better: https://x.com/foundmyfitness/status/1955294334535995850?lang=en https://x.com/foundmyfitness/status/1955294334535995850?lang...
    - PaulDavisThe1st 6mo ago
      David Roche, a notable running coach (and runner), and his co-coaching wife (and runner) Dr. Megan Roche (MD/PhD) seem to think that hot tubs need to be at least 106F to generate much of a heat shock response, which is normally what one is looking for in the context of post-exercise heat exposure. I should note, however, that they are mostly reading the same research papers as everybody else, not doing primary studies themselves.
      - pstuart 6mo ago
        Being that the recommended max temperature for hot tubs is 104F that could be an issue. Hot tubs are definitely more pleasurable than saunas, and if it comes "close enough" I'd be fine with that.
  - Tor3 6mo ago
    As someone with access to both Japanese ofuro and sauna, they are quite different in some respects. And similar in others. One thing which a sauna could do for me when the ofuro could not, was to fix a problem I had with coughing. Something which plauged me for a long time, and which the doctors couldn't find any reason for, but I had such painful daily coughs that it really bothered me. Couldn't sleep on my back either. Then I noticed that if I used the sauna daily, and carefully breathed hot air, the symptoms lessened. And after going for the daily sauna regime (instead of occasionally) for some time, the coughing problem I had for years finally disappeared. The hot baths did nothing for this (but was good for other things, e.g. muscle pains. And essential for being able to sleep at cold winter nights in non-insulated Japanese homes.. heating up the body with a very long very hot bath does wonders)
- Noaidi 6mo ago
  Just because your heart rate is lower does it mean you’re any healthier however. This is just ridiculous measurement it means nothing. The sauna might be acting like any other drug. There are a lot of drugs that will lower nighttime heart rate. Does that mean those drugs are healthier for you?
  - PaulDavisThe1st 6mo ago
    If your resting heart rate is lower without any drugs, it indicates that your heart can cause sufficient oxygen to be delivered to your organs with less effort than if it were higher. That can be caused by a variety of things (including stroke volume, capillary dilation and general obstruction (or not) of blood vessels). These are all good proxies for general health. Drugs lowering your resting heart rate do not indicate this in the same way.
    - Noaidi 6mo ago
      You think being n a Sauna is not a drug (effectively)?
- oidar 6mo ago
  Also not controlled: Maybe on Sauna days they drank more water before bed? Or less alcohol?
- p1anecrazy 6mo ago
  Appreciate it as a regular sauna-goer. I am also struggling to wake up after sauna evenings and maybe you research explains why
- vinni2 6mo ago
  A lot of people go to sauna after workout. I rarely go to sauna without workout so not sure if the combination is helping me or exercise or the sauna. How to control for that?
  - marcosdumay 6mo ago
    You are replying to a comment that said they log and control for time of activity.
- socalgal2 6mo ago
  > Sauna days are more active, which fits how people actually use saunas, often as a post‑workout routine WAT? As far I as know there is no such connection between workouts and saunas in Finland, nor in Japan
- Tor3 6mo ago
  From the article: "..promotes sweating and therefore the elimination of toxins,.." That false statement really makes me unsure about the quality of the article. And I'm saying this as someone who uses sauna daily, when possible (I have one at home, and I grew up with saunas). "De-toxification" by sweating is a myth. Sweat glands are very simple organs (think salt on one side, which results in pressure, i.e. osmosis) and can't do anything of the sort. You'll be much better off peeing. Saunas probably have good health effects. I'm certainly happy as a sauna user. But there's no de-toxification in this.
  - Ey7NFZ3P0nzAe 6mo ago
    > You'll be much better off peeing. Actually, the rate of blood filtration by kidney glomerulae is pretty constant and independent of the amount of urine in your bladder. Except if you overflow to the point of drowning your kidney of course.
    - Tor3 6mo ago
      Yes.. my point was only that to get rid of more than water you're better peeing than sweating. In any case, the liver is the only toxin-handling organ in the body (and a complex one).
  - majkinetor 6mo ago
    Actually, this is why one shouldn't believe HN comments about medicine. The quality is this low. This is simply laughable and very easily checked out. Here is one random study: https://link.springer.com/article/10.1007/s00244-010-9611-5 https://link.springer.com/article/10.1007/s00244-010-9611-5 > Many toxic elements appeared to be preferentially excreted through sweat Here is another quick one https://onlinelibrary.wiley.com/doi/full/10.1155/2012/184745 https://onlinelibrary.wiley.com/doi/full/10.1155/2012/184745 > Sweating deserves consideration for toxic element detoxification. Its even observable directly - just go next to the heavy smoker during exercise. While it might be less than dedicated organs, the skin is the largest organ by far. Ofc, the topic is debated like every single thing in medicine, but calling it a myth is nonsence.
- deleted 6mo ago
  [deleted]
- alfiedotwtf 6mo ago
  Time of day could make a huge difference - if they did this close to sleeping, their body would be hot while winding down, and so would use less layers. If they fell asleep with only a sheet compared to multi-layered thick covers, their temperature would be lower for the whole night. I know n=1, but when I started sleeping with only a sheet, my heart rate was at my lowest - my Apple Watch would ping multiple times a night because it was below 40. Can’t comment about being cold anymore because these days I sleep on top of a spiked mat which makes my back feel like it’s on fire for the whole night.
stevekemp 6mo ago
[flagged]
- KeplerBoy 6mo ago
  There are different kinds of saunas. Nobody gets into a 90c humid sauna, that would just kill you.
  - preya2k 6mo ago
    Oh I can assure you, millions people in the northern europe do exactly this ;) EDIT: I guess it depends on your definition of "humid". But 90C and regular water infusions are pretty common sauna conditions.
    - renewiltord 6mo ago
      I mean yes it depends on your definition of humid but if your definition of humid is under 20% RH then that's not in agreement with any other humans on the planet and if it's over 50% RH then no, millions of people are not doing this because they would die. Our bedroom is at 50% RH because under that our baby's skin dries out. There's no way anyone is sitting in a 90 C 50% RH sauna for any appreciable amount of time. They would die.
  - hilariously 6mo ago
    I guess I am a revenant - I get into one regularly in my basement.
  - victorbjorklund 6mo ago
    Haha no, I been in 90c saunas many times. Can I stay there for a long time? Heck no. But some people can and it doesn’t kill you (maybe if you have some preexisting condition)
    - KeplerBoy 6mo ago
      the point is the humidity. hot saunas need to be relatively dry otherwise your sweat won't evaporate.
ckrapu 6mo ago
I can tell you wrote the article with ChatGPT. I’m out as soon as I pick up the smell. I don’t dislike the usage of AI, I just don’t trust. It if you haven’t written it yourself.
- flippyhead 6mo ago
  I feel like we need an acronym for this kind of comment. I am pretty sure approximately 100% of HN posts now include at least one comment where someone, somehow, knows that an article is written by AI and resents it. For Claude we have the ever present "you are absolutely right" and this is like it's human mirror. Something like TLDR; but meaning "uhg, written by AI".
  - thundergolfer 6mo ago
    This article is a brilliant skewering of the 'em dash means LLM' heuristic as a broken trick deployed by those too-clever-by-half. 1. https://www.scottsmitelli.com/articles/em-dash-tool/ https://www.scottsmitelli.com/articles/em-dash-tool/
    - flippyhead 6mo ago
      Thank you for this. This is like finding a book where someone has written down what I've been thinking, but better than I ever could.
    - joks 6mo ago
      In fairness it's more than the em dash with this article. Read the first 3 bullet points.
  - eudamoniac 6mo ago
    AI;DR
  - WaltPurvis 6mo ago
    We don't need an acronym; people just need to stop posting these utterly worthless comments.
deleted 6mo ago
[deleted]
sva_ 6mo ago
> Motivated to understand the immediate physiological response to saunas, we looked at the same-day effects across ~59,000 daily records from 256 users. Editorialized title is wrong. n=256
- kyriakosel 6mo ago
  Fair flag: 256 users, 59k days
- deviation 6mo ago
  @dang can fix this right up, I believe
Aurornis 6mo ago
n= traditionally refers to the number of participants, not the number of data points. The headline claim is very misleading for anyone who thought there were 59,000 people in this data set. The absolute difference is also small. Small enough that the effect might be attributable to something secondary, such as sauna users consuming more water in recovery and being more hydrated. Heart rate has a relationship with hydration status.
amazingamazing 6mo ago
N=256
iwontberude 6mo ago
Website doesn’t load, it times out. Anyone have tl;dr?
- kyriakosel 6mo ago
  it works for me - what browser are you using?
  - cpncrunch 6mo ago
    Its a cloudflare gateway timeout, so not working for anyone on any browser right now. Seems like a contradiction if cloudflare cant cache what is presumably a static site.
    - kyriakosel 6mo ago
      indeed - fixed now, let me know if you can see it!
      - cpncrunch 6mo ago
        Yes working now.
        kyriakosel 6mo ago
        great
gcanyon 6mo ago
N=1, but I started rowing (indoor, on an erg) an hour a day -- not hard, generally 120-140 bpm -- every day starting February 28, after rowing inconsistently for a year or more before that. My resting (not sleep) pulse has dropped by 10% over the past ~7 weeks, from 60 to 54.
- PaulDavisThe1st 6mo ago
  General advice: citing absolute HR numbers is pretty meaningless for a broad audience, because they are not intepretable. Express them as percentages of your current max HR to be meaningful to others.
  - gcanyon 6mo ago
    As I said, N=1 so the post was meaningless before I said another word :-) For your benefit: my max is somewhere around 175, maybe 180, which is high for my age. I'm also unusual in that even my max heart rate doesn't lead to lactic acid buildup, for what it's worth.
strangescript 6mo ago
Anecdotal, of course, but the biggest change I ever made in my life was right before bed: take a screaming hot shower with dim lighting. I'd say 95% of the time, I get in bed and just pass out and have no real memory of time passing before falling asleep.
- Arch485 6mo ago
  Increasing skin temperature is known to induce sleep (can't find a source currently, sorry). Something about your skin being warmer allowing your body to cool more effectively, I think. So a hot shower before bed is actually great for sleep, because you get the increased skin temp, relaxed muscles from the warm water, and general relaxation because showers are (for many people) relaxing.
  - something765478 6mo ago
    That's funny, I find it much easier to fall asleep in a cold environment. Then again, I also like to use a heavy blanket, so maybe it's the weight more than the cold that's helping me.
    - WastedCucumber 6mo ago
      I think that's also consistent with the idea behind a hot shower. The shower doesn't help by increasing your body temperature, in fact it does the opposite. The hot shower induces the body to try to cool down, so near-skin blood vessels swell, and that dumps heat into the cold air, which reduces your core temperature, and a reduced core temperature helps you fall asleep. I think where I read about this was Why We Sleep from Matthew Walker. But he suggests just washing your face with warm water, as opposed to a shower.
  - pawelduda 6mo ago
    Hot shower heats up your body, which causes it to direct blood away from the core to cool it down so it doesn't overheat. Dropping core temp triggers the brain to ramp up melatonin production. Or so I heard. Conversely, when the temperature drops, your body directs blood away from your hands and legs because core has higher priority for survival
SCdF 6mo ago
Not to be glib, but being dead lowers your night time heart rate more then exercise as well. Is having a lower night time heart rate the core goal of exercise? Is it even a goal at all? Or is it just an indicator of other goals being reached? I'm genuinely curious, I wasn't aware that the number mattered, more than what that number actually represents.
- SJMG 6mo ago
  It's just another measure. It's not ceteris paribus better to have a lower one. From the author, "Strongest hypothesis: elevated parasympathetic tone from the post-sauna cooling phase carries into sleep" AKA, they use it as a proxy to infer a deeper state of rest and improved recovery state. Says nothing about the fatigue generated from using a sauna.
- nonameiguess 6mo ago
  No, immediately lowering heart rate isn't a goal of exercise. The reason it's a meaningful measure at all is because a lower resting heart rate, not overnight in response to a stimulus, but a permanently lower resting heart rate, is a sign that your overall cardiorespiratory system has become more efficient in terms of how much blood it can deliver per beat, how much oxygen it can deliver per unit of blood, and how much energy can be generated per unit of oxygen in your mitochondria. When those efficiencies improve, fewer beats per minute results in the same level of work done in your cells. Thus, resting heart acts as a proxy measure of aerobic fitness, not a goal in and of itself. All of those are long-term adaptations. Conversely, there are many ways to acutely lower heart rate that are clearly not healthy. Death, obviously, but taking opioids or many other kinds of depressants, not moving ever, sleeping 23 hours a day, will all lower your average heart rate immediately without making you fitter or healthier.
- asdfman123 6mo ago
  The goal is improving cardiovascular fitness, and a low heart rate means your cardiovascular system is operating efficiently.
shevy-java 6mo ago
Well ... Finland life expectancy for 2023 was 81.69. Norway life expectancy for 2025 was 83.23. Japan life expectancy for 2025 was 85.27. Sumo wrestlers in Japan have a life expectancy between 60-65 years or so - significantly lower than the other japanese. I am not saying that sauna has no positive effect at all, but I would reason that the number one risk factor is ... weight. And I'd also still say that exercise is correlated here, if only secondary, e. g. you may be able to maintain better bodily functions if you exercise, if you can avoid injury. I do not think that going into the sauna rather than e. g. light running for 5 to 10 minutes or so, is anywhere near on the same level.
- chasebank 6mo ago
  News at 9, shorter people on average live longer than taller people...
  - movie_fan25 6mo ago
    Unless you are from Norway or Finland, evidently.
dukeofdoom 6mo ago
Seems to me what we now know about neural networks, we should maybe weighted sum of inputs, that fire off the desired output. The human body/brain process all kinds of stimulus at once, and might only react to a combination of inputs.
YmiYugy 6mo ago
I know that for myself exercise increases my resting heart rate in the short term. It only decreases after a day or two, sometimes more depending on how fatigued I am. I thought that was common, with recovery times obviously decreasing the fitter ones gets.
storus 6mo ago
Can anyone suggest why after covid I can't do Finnish sauna anymore? Prior to that I used to do 1-2x a week a sequence of 5x(10 minutes in sauna + 5 minutes cold water immersion + 10 minutes rest) which was absolutely great for both stress reduction and blood flow. Now if I do 5 minutes in sauna I feel like my skin was burning and I am about to die, and I need to recover for 1 hour from that to be able to just walk away from sauna.
- mcv 6mo ago
  No idea. How hot is and was your sauna? Is it possible that it's hotter than it used to be? Maybe try one that's slightly less hot? I've got the opposite problem: saunas don't seem to be able to make me sweat anymore, so I'm looking for the hottest saunas I can find.
  - storus 6mo ago
    The usual 95"C, nothing extraordinary. Sweating after covid got impaired, I might have some thermoregulation issue.
    - mcv 6mo ago
      95 is pretty hot. At commercial spas I see them start at 70, and rarely above 90.
      - storus 6mo ago
        95 is normal where I live for Finnish saunas. Then there are other types of saunas that start lower, but Finnish are always around 95.
        jampekka 6mo ago
        95 is high for Finnish saunas in Finland at least. Public saunas are very rarely so hot here, and few like it that hot. Edit: to put it into some numbers, per one study[1] Finnish sauna sessions were on average at 75.9°C with SD 9.9°C. If we assume normal distribution, that means that more than 97 % of sauna sessions are at < 95°C. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6262976/ https://pmc.ncbi.nlm.nih.gov/articles/PMC6262976/
nickburns 6mo ago
Why is this quackery front page?
redeux 6mo ago
I didn’t see a reference to the amount of time in the sauna required to receive this effect. Was that measured as part of this research?
eggy 6mo ago
A delta of 3 bpm on sauna days corresponds to around 4% delta if the baseline is 72 bpm. I've gone from a resting heart rate over a 7-day average of 64 bpm to 58 bpm by jumping 15 min. of rope a day, 4 times a week. I've lost weight, body fat, and I feel like my body is more efficient with corresponding lower heart rates throughout my active day. I like saunas for recovery and aches, they put me in a relaxed state after, and I believe the dilation is flushing my system. Like anything else, moderation. Perhaps I will add sauna to my weekly routine 1x per week or less.
- asdfman123 6mo ago
  PSA: if you like saunas but don't have easy access to one, those IR sauna bags you can buy online work great. Some people find it gross to basically sweat inside a powered sleeping bag, but if you don't mind that you can get the same effects of a sauna while lying on your (covered) couch and watching YouTube.
  - sd9 6mo ago
    Wow, they look really quite dangerous. I wouldn’t want to pass out in one. Yeah you can pass out in a sauna too, but it feels easier to lurch for the door than to fight with a sleeping bag.
    - asdfman123 6mo ago
      There's a timer shutoff. I know I can sit in mine for the full hour at the highest setting, so it's not anything my body can't handle. You can set it for less time at a lower heat setting, too.
- jrussino 6mo ago
  > I've gone from a resting heart rate over a 7-day average of 64 bpm to 58 bpm by jumping 15 min. of rope a day, 4 times a week. Over how long of a time period?
  - eggy 5mo ago
chris_va 6mo ago
This would not pass peer review for a journal as written. Maybe the conclusion is correct, or maybe not, but as written the methodology is under specified, statistics are not supported, and there too many confounders not addressed. One should not take anything from this without a better write up. Just misunderstanding what n= means is a huge flag. Since the author is here, I have to ask: Why a blog post and not an actual paper? Why spray this onto the internet without validating the work? Or, conversely, why not caveat the work as exploratory data science?
smm11 6mo ago
I feel better after sitting in a steam room two or three times a week. That's proof enough for me.
vitto_gioda 6mo ago
I also recommend reading about the effects on microplastics studied by Blueprint: https://cptsd.sites.umassd.edu/bryan-johnson-and-microplastics-reduced-plastics-by-93/ https://cptsd.sites.umassd.edu/bryan-johnson-and-microplasti...
MyHonestOpinon 6mo ago
I try to do 180 minutes a week of cardio. Mostly Zone 2. Biking, elliptical, tKD. But once in a while my legs feel too tired, so I complete my weekly minutes going to the steam room. It makes sense to me since it raises your heart rate. Also, my samsung watch can measure stress (whatever it means). It always shows the very, very minimal stress for me. The only time that I have been stressed was the day that I spent a bit too much on the steam room.
- asdfman123 6mo ago
  FWIW you should probably be doing some max intensity, or at least high intensity cardio. Zone 2 is great but the best health outcomes are from people who do high intensity exercise interspersed with zone 2 exercise.
  - PaulDavisThe1st 6mo ago
    This is contested by a significant number of contemporary running coaches (see, for example "Training for Uphill Athletes" by Steve Johnson or any of the life work of Phil Maffetone. HIIT is quite effective at something; it's not clear that it is effective at all possible exercise goals (including, but not limited to, endurance running). Johnson in particular says that unless you've already narrowed the gap between your "first" and "second" (anaerobic) threshold to 5%, HIIT really doesn't make much sense because you're "aerobically challenged" and need to work on that first, which he believes (with significant evidence) is best done almost entirely in zone 2. He also notes that someone like Eliud Kipchoge can spend 2 hours running 4:30 min/mile pace, so that is clearly within his aerobic range, but that Kipchoge would never and should never spend much time training at that pace because of the load it would put on his system. So the zones that are used for training purposes depend significantly on the current fitness level of the athlete. I have used HIIT effectively to get myself out of certain fitness/training "ruts", but I think that the zone 2 folks have somevery cogent and coherent observations and advice.
    - mchusma 6mo ago
      I think one issue I have with Zone 2 proponents is that it makes sense that if you can do a lot more stuff at Zone 2 than you can at less. For most endurance athletes, the volume of running beats everything else in terms of efficacy. However, most of us don't have unlimited time. For example, if I do a week of 3x30 minute swssions at Zone 2, my fitness is going to plummet. But if I do one at Zone 2, one at tempo, and one set of intervals, I'm at least maintaining fitness. Would 5 hours at zone 2 be better? Absolutely. But I dont always have the time.
atum47 6mo ago
Should I assume a steam room has the same effect? I prefer it over sauna
- dtran 6mo ago
  Potentially, but likely much less effective and less studied, and you likely need longer sessions for effective dosage. Most of the studies I've seen on improvements in blood plasma volume from passive heat are usually done with sessions in saunas with temperatures > 150 degrees F (60 C). Steam rooms usually only get up to 120F (~49C) even though the humidity probably makes it feel warmer. Copying and pasting some of my reply to another comment above
  - PaulDavisThe1st 6mo ago
    Sweating is one the main triggers for an increase in blood plasma volume, and the humidity level of a steam room causes vastly higher rates of sweating than most saunas do. You can lose significant body heat by sweating in a dry environment, but much less in high humidity. Consequently, your body needs to sweat much more rapidly even though the absolute temperature may be lower.
    - dtran 6mo ago
      To my understanding, while sweating is important to heat adaptation and blood plasma volume adaptations, thermal load and cardiovascular strain are likely bigger factors (and more important for the health benefits mentioned in this study). Overall thermal load is still higher in a hotter dry sauna than in a steam room
      - PaulDavisThe1st 6mo ago
        That's not my understanding, but my understanding is somehwere between 3rd and 6th hand, so it's likely not worth much.
- kyriakosel 6mo ago
  that would be interesting to study - let me follow up on this
kp988 6mo ago
I use the sauna every day and highly recommend it to everyone, it's great for your health and for stress
michaelteter 6mo ago
My anecdotal experience: TLDR: regular sauna seems to have no effect on my resting HR. Extended high HR cardio definitely does. I became a huge fan of sauna time (15-20 minutes at approx 175F/80C... I would prefer a bit warmer, but I had no control). It was like shower time, or meditation time (which I never took time for). Great thinking time. I'd use it after a workout, but I would also use it on days without a workout. I've been tracking some stats via my Garmin watch for a few years, and I've identified some patterns - particularly regarding resting HR. The most significant reducer of resting heart rate for me is running (5k). Periods where my training includes regular 5k runs cause my resting HR to drop by 5-8 bpm. Most of my training is resistance, although in the last 6 months I've added in a lot more cardio. Stairs and rowing do not seem to noticeably reduce my resting HR. Running definitely does. But to be fair, maybe it's not the running but rather the active HR I'm sustaining. Despite trying to stay in the aerobic zone, running always pushes me to zones 4 and 5. So 50% of my 30 minutes of exercise will be in my max zone. With stairs or rowing, I can keep my HR in aerobic and threshold. Some stats: When I'm off my fitness routine, living life as a typical person, my resting HR is 65. When I'm on a resistance fitness routine, my resting HR is 58. When I'm also running, the rHR is 51. If I eat a heavy meal too close to bedtime, my rHR is +15. If I drink a lot of alcohol before sleeping, rHR can be +20! Food + alcohol = WTF. Probably not good.
manapause 6mo ago
As an amateur sauna evangelist, I can say my experience sauna usage 1-2 times a week has greatly improved my life and quality of sleep!
deleted 6mo ago
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theshrike79 6mo ago
Correct me if I'm wrong, but I thought HRV (Heart Rate Variability) is a bigger positive correlation for health than low heart rate?

448 points by kyriakosel 6mo ago

Author here. Methodology upfront because I'd ask the same things: Data: daily records from wearable users who logged sauna sessions via connected apps. Within-person design — each user is their own control, comparing their own sauna-day nights against their own non-sauna-day nights. No cross-user comparisons. Stats: paired t-tests, FDR-corrected p < 0.05, Cohen's d > 0.2 threshold for "meaningful effect." Anything below d=0.2 we don't report as a finding. What we measured: minimum nighttime HR, max and average HR, HRV, activity minutes and distance, menstrual cycle phase (for female subset). What we found: - On sauna days, minimum nighttime HR drops ~3 bpm (~5%) vs. the same user's non-sauna days. - Effect survives controlling for activity level. It's not "sauna users just exercised more that day." - Strongest hypothesis: elevated parasympathetic tone from the post-sauna cooling phase carries into sleep. Consistent with heat-stress physiology literature. - Sex difference: for women, the nighttime HR effect only crosses the d > 0.2 threshold during the luteal phase. No meaningful effect during the follicular phase. We didn't expect this; worth replicating. What we can't control for: - Sauna type (dry / infrared / steam), duration, temperature. Not captured. - Dose-response. We don't know session length per user. - Timing of sauna relative to sleep. - Reverse causation: people may sauna on days they already feel recovered. - Selection: wearable users who bother logging sauna are a health-conscious cohort. What surprised us: the effect is larger than what we see for comparable-intensity exercise days. If you treat nighttime HR as a parasympathetic recovery signal, sauna beats a moderate workout on the same user. Not what I'd have predicted.

itsthecourier 6mo ago
how does this reduction in heartbeat at night affect the body?
croemer 6mo ago
Why didn't you put the methodology in the post? Also, which devices were used to record? How do you know people went to sauna?
bluGill 6mo ago
The most important thing you didn't measure: does this affect long term health in the same way exercise it known to. That is can I put a TV in my sauna and watch that for an hour every day instead of getting out and exercising - yet get the same better long term health outcomes? My current guess is no. That is this improves a marker for good health without improving health. However this is a guess by someone who isn't in the medical field and so could be wrong.
- testing22321 6mo ago
  I don’t think the TV in the sauna will have long term health outcomes.
  - Filligree 6mo ago
    It will certainly affect the health of the TV.
- kyriakosel 6mo ago
  Agreed - one is muscular/metabolic demand, the other (sauna) is thermoregulation. Agreed on the long-term effect too: doing a study on long term health is a completely different story
- nsbk 6mo ago
  I recently listened to a podcast about the benefits of sauna or deliberate heat exposure and the gist is that if you get your core temperature at about 39 degrees celsius your cardiovascular system is working comparably hard to light exercise. My take is that your heart and lungs are working out, even if your body is not. Do you get the same benefits as going for a run or bike ride for a comparable amount of time? no, since your limbs don't get fit, but your heart and lungs do.
  - mminer237 6mo ago
    Edit: I posted this accidentally when editing without noticing. Hypertrophy isn't necessarily a bad thing. I thought I was discarding the comment cuz I realized I was out of my depth. whoops Please ignore my comment, though I will leave it to make the below comments less confusing. Original: You don't want to "work out" your heart though. Cardiac hypertrophy is a bad thing. The benefit of exercise is that your muscles become more oxygen-efficient. Your heart endures some stress now, so that it can work less in the future.
gamerslexus 6mo ago
It would be very interesting if lowering night heart rate only happens with certain sauna type. > What we can't control for: - Sauna type (dry / infrared / steam), duration, temperature. Not captured Could probably capture humidity/duration/temperature using a sensor in wearable device...
- kyriakosel 6mo ago
  we agree - but thats not that simple :)
  - methyl 6mo ago
    > who logged sauna sessions via connected apps It seems you ask participants to log if they went to sauna. Out of curiosity, why is it not simple to also ask for a type?
    - kyriakosel 6mo ago
      i was mostly refering to humidity/duration/temperature given that most devices do not report back these values
      - austinthetaco 6mo ago
        I'm equally confused as the other person above. Why not just ask participants to report what type of sauna they used? Sure humidity/duration/temp would be awesome to have, but at the very minimum knowing if a dry sauna would get the same results as a traditional steam sauna.
        gamerslexus 6mo ago
        What if they jumped between saunas? And with self-reporting, the more you ask I guess the less precise the result... Sensors, however...
        PaulDavisThe1st 6mo ago
lccerina 6mo ago
If this was a peer-reviewed paper, it won't pass. - Is the wearable accurate enough to be sure that 3bpm is not a measurement fluke? - Why did you use the minimum heart rate value (which could be a measurement glitch) and did not compare a percentile (e.g., 2.5th lowest percentile)? - Were all assumptions for paired t-testing valid? How did you account for likely temporal correlations in the data (e.g., sauna could have an effect also on a night 2 days after it, same for exercise)? - How can you define a "comparable-intensity exercise day" if you don't know the characteristics of the sauna?
- joelthelion 6mo ago
  > Is the wearable accurate enough to be sure that 3bpm is not a measurement fluke If the statistical tests show significance (and are valid), the answer to this question is yes. If you have enough data you can make strong conclusions even witwith imperfect hardware.
  - gjulianm 6mo ago
    Unless the effect they're measuring is that the wearable measures differently in sauna days.
  - ranguna 6mo ago
    Strong conclusion that the hardware is precisely imperfect?
  - lccerina 6mo ago
    Not at all, if you have a lot of data coming from imperfect hardware (which can mean both a fixed bias and unknown variance), and you don't know the variance for plenty of practical reasons, you are left with a result that is statistically significant, but wrong
jtanderson 6mo ago
Just as a discussion point: how do you think these effects would translate (if at all) to regularly practicing hot yoga, say around 100-105F? Intuitively, it would combine the effort + recovery, but probably not enough time elapsed in the same session for the sweat benefit during muscle repair?
Glemllksdf 6mo ago
Or the sauna is a relaxing thing like a happy place and that reduces heart rate?
gjulianm 6mo ago
> Effect survives controlling for activity level. How did you control for activity level? Do you have similar BPM plots for the different situations (sauna+exercise, sauna+no exercise, no sauna + exercise, no sauna + no exercise) for a visual representation? > minimum nighttime HR drops ~3 bpm (~5%) What wearables were used? These devices don't usually have enough precision to reliably detect ~3bpm changes. Also, the measurements are sensitive to skin, blood flow changes and temperature. How do you know the difference doesn't come from different sensor behavior after sauna?
- jampekka 6mo ago
  > What wearables were used? These devices don't usually have enough precision to reliably detect ~3bpm changes. For large sample averages this doesn't really matter.
  - gjulianm 6mo ago
    It does, specially if the error bars from multiple measurements show higher precision than what would be expected.
    - jampekka 6mo ago
      I don't understand what you mean by that. Precision (inverse of variance) of estimate of mean increases directly proportional to number of samples (given some assumptions that very likely hold here). If you have measurement standard deviation of say 10 bpm, with 100 measurements you have mean estimate standard deviation of 10/sqrt(100) = 1 bpm.
      - gjulianm 6mo ago
        > of estimate of mean But you can't really assume that the estimate of the mean represents the real value. For example, if the sensor is equally likely to show 80 or 81 BPM when the real heartrate is 80.7, the mean estimator will be biased. > with 100 measurements Also, wearables aren't taking 100 measurements of the BPM at a given point in time. I think the highest frequency they usually have is 1 second measurement interval. So they don't really have a lot of measurements for each point in time. > mean estimate standard deviation That's the standard deviation of the mean of the values. Doesn't imply that the standard deviation of the values themselves will go to zero. > I don't understand what you mean by that. That as a rule of thumb, you should not assume that repeating measurements will give you more precision than what the tool can offer. E.g., trying to measure down to milimeters with a ruler that has only 1cm marks will not really work well.
al_borland 6mo ago
How would this play out over time? Will sauna see a 3bpm drop below baseline on days it’s used, while keeping the same baseline? Exercise, over time, should lower the baseline (to a point). I’d think this would have the more desirable long term benefits. One can do both, of course, but when people see headlines like this they often jump to the conclusion that sauna can replace exercise, because that’s what they want to believe.
- verst 6mo ago
  Due to lots of long distance running my rest heart rate is below 40. I am highly skeptical I would experience a 3bpm lower heart rate after sauna. Maybe this benefit applies after infrequent activity or less intense activity only.
jampekka 6mo ago
I'd like to see a bit more detailed methods. - How was the controlling for the other factors done? A linear model? - What were the sauna vs non-sauna baseline HRs in fig 1? Could you plot raw averages? - Was the min HR explicitly computed during the night (in Fig 2), or was it assumed min HR occurs during the night? - Reporting only significant results is not prudent even with multiple comparisons corrections, please report all tests made
lazyant 6mo ago
Would a hot tub session (say at 100 - 105 F) be comparable or yield similar results?
- pstuart 6mo ago
  Dr. Rhonda Patrick has been beating the drum for saunas for a long time, and she's reported that a hot tub can be equivalent or better: https://x.com/foundmyfitness/status/1955294334535995850?lang=en https://x.com/foundmyfitness/status/1955294334535995850?lang...
  - PaulDavisThe1st 6mo ago
    David Roche, a notable running coach (and runner), and his co-coaching wife (and runner) Dr. Megan Roche (MD/PhD) seem to think that hot tubs need to be at least 106F to generate much of a heat shock response, which is normally what one is looking for in the context of post-exercise heat exposure. I should note, however, that they are mostly reading the same research papers as everybody else, not doing primary studies themselves.
    - pstuart 6mo ago
      Being that the recommended max temperature for hot tubs is 104F that could be an issue. Hot tubs are definitely more pleasurable than saunas, and if it comes "close enough" I'd be fine with that.
- Tor3 6mo ago
  As someone with access to both Japanese ofuro and sauna, they are quite different in some respects. And similar in others. One thing which a sauna could do for me when the ofuro could not, was to fix a problem I had with coughing. Something which plauged me for a long time, and which the doctors couldn't find any reason for, but I had such painful daily coughs that it really bothered me. Couldn't sleep on my back either. Then I noticed that if I used the sauna daily, and carefully breathed hot air, the symptoms lessened. And after going for the daily sauna regime (instead of occasionally) for some time, the coughing problem I had for years finally disappeared. The hot baths did nothing for this (but was good for other things, e.g. muscle pains. And essential for being able to sleep at cold winter nights in non-insulated Japanese homes.. heating up the body with a very long very hot bath does wonders)
Noaidi 6mo ago
Just because your heart rate is lower does it mean you’re any healthier however. This is just ridiculous measurement it means nothing. The sauna might be acting like any other drug. There are a lot of drugs that will lower nighttime heart rate. Does that mean those drugs are healthier for you?
- PaulDavisThe1st 6mo ago
  If your resting heart rate is lower without any drugs, it indicates that your heart can cause sufficient oxygen to be delivered to your organs with less effort than if it were higher. That can be caused by a variety of things (including stroke volume, capillary dilation and general obstruction (or not) of blood vessels). These are all good proxies for general health. Drugs lowering your resting heart rate do not indicate this in the same way.
  - Noaidi 6mo ago
    You think being n a Sauna is not a drug (effectively)?
oidar 6mo ago
Also not controlled: Maybe on Sauna days they drank more water before bed? Or less alcohol?
p1anecrazy 6mo ago
Appreciate it as a regular sauna-goer. I am also struggling to wake up after sauna evenings and maybe you research explains why
vinni2 6mo ago
A lot of people go to sauna after workout. I rarely go to sauna without workout so not sure if the combination is helping me or exercise or the sauna. How to control for that?
- marcosdumay 6mo ago
  You are replying to a comment that said they log and control for time of activity.
socalgal2 6mo ago
> Sauna days are more active, which fits how people actually use saunas, often as a post‑workout routine WAT? As far I as know there is no such connection between workouts and saunas in Finland, nor in Japan
Tor3 6mo ago
From the article: "..promotes sweating and therefore the elimination of toxins,.." That false statement really makes me unsure about the quality of the article. And I'm saying this as someone who uses sauna daily, when possible (I have one at home, and I grew up with saunas). "De-toxification" by sweating is a myth. Sweat glands are very simple organs (think salt on one side, which results in pressure, i.e. osmosis) and can't do anything of the sort. You'll be much better off peeing. Saunas probably have good health effects. I'm certainly happy as a sauna user. But there's no de-toxification in this.
- Ey7NFZ3P0nzAe 6mo ago
  > You'll be much better off peeing. Actually, the rate of blood filtration by kidney glomerulae is pretty constant and independent of the amount of urine in your bladder. Except if you overflow to the point of drowning your kidney of course.
  - Tor3 6mo ago
    Yes.. my point was only that to get rid of more than water you're better peeing than sweating. In any case, the liver is the only toxin-handling organ in the body (and a complex one).
- majkinetor 6mo ago
  Actually, this is why one shouldn't believe HN comments about medicine. The quality is this low. This is simply laughable and very easily checked out. Here is one random study: https://link.springer.com/article/10.1007/s00244-010-9611-5 https://link.springer.com/article/10.1007/s00244-010-9611-5 > Many toxic elements appeared to be preferentially excreted through sweat Here is another quick one https://onlinelibrary.wiley.com/doi/full/10.1155/2012/184745 https://onlinelibrary.wiley.com/doi/full/10.1155/2012/184745 > Sweating deserves consideration for toxic element detoxification. Its even observable directly - just go next to the heavy smoker during exercise. While it might be less than dedicated organs, the skin is the largest organ by far. Ofc, the topic is debated like every single thing in medicine, but calling it a myth is nonsence.
deleted 6mo ago
[deleted]
alfiedotwtf 6mo ago
Time of day could make a huge difference - if they did this close to sleeping, their body would be hot while winding down, and so would use less layers. If they fell asleep with only a sheet compared to multi-layered thick covers, their temperature would be lower for the whole night. I know n=1, but when I started sleeping with only a sheet, my heart rate was at my lowest - my Apple Watch would ping multiple times a night because it was below 40. Can’t comment about being cold anymore because these days I sleep on top of a spiked mat which makes my back feel like it’s on fire for the whole night.

stevekemp 6mo ago

[flagged]

KeplerBoy 6mo ago
There are different kinds of saunas. Nobody gets into a 90c humid sauna, that would just kill you.
- preya2k 6mo ago
  Oh I can assure you, millions people in the northern europe do exactly this ;) EDIT: I guess it depends on your definition of "humid". But 90C and regular water infusions are pretty common sauna conditions.
  - renewiltord 6mo ago
    I mean yes it depends on your definition of humid but if your definition of humid is under 20% RH then that's not in agreement with any other humans on the planet and if it's over 50% RH then no, millions of people are not doing this because they would die. Our bedroom is at 50% RH because under that our baby's skin dries out. There's no way anyone is sitting in a 90 C 50% RH sauna for any appreciable amount of time. They would die.
- hilariously 6mo ago
  I guess I am a revenant - I get into one regularly in my basement.
- victorbjorklund 6mo ago
  Haha no, I been in 90c saunas many times. Can I stay there for a long time? Heck no. But some people can and it doesn’t kill you (maybe if you have some preexisting condition)
  - KeplerBoy 6mo ago
    the point is the humidity. hot saunas need to be relatively dry otherwise your sweat won't evaporate.

ckrapu 6mo ago

I can tell you wrote the article with ChatGPT. I’m out as soon as I pick up the smell. I don’t dislike the usage of AI, I just don’t trust. It if you haven’t written it yourself.

flippyhead 6mo ago
I feel like we need an acronym for this kind of comment. I am pretty sure approximately 100% of HN posts now include at least one comment where someone, somehow, knows that an article is written by AI and resents it. For Claude we have the ever present "you are absolutely right" and this is like it's human mirror. Something like TLDR; but meaning "uhg, written by AI".
- thundergolfer 6mo ago
  This article is a brilliant skewering of the 'em dash means LLM' heuristic as a broken trick deployed by those too-clever-by-half. 1. https://www.scottsmitelli.com/articles/em-dash-tool/ https://www.scottsmitelli.com/articles/em-dash-tool/
  - flippyhead 6mo ago
    Thank you for this. This is like finding a book where someone has written down what I've been thinking, but better than I ever could.
  - joks 6mo ago
    In fairness it's more than the em dash with this article. Read the first 3 bullet points.
- eudamoniac 6mo ago
  AI;DR
- WaltPurvis 6mo ago
  We don't need an acronym; people just need to stop posting these utterly worthless comments.

deleted 6mo ago

[deleted]

sva_ 6mo ago

> Motivated to understand the immediate physiological response to saunas, we looked at the same-day effects across ~59,000 daily records from 256 users. Editorialized title is wrong. n=256

kyriakosel 6mo ago
Fair flag: 256 users, 59k days
deviation 6mo ago
@dang can fix this right up, I believe

Aurornis 6mo ago

n= traditionally refers to the number of participants, not the number of data points. The headline claim is very misleading for anyone who thought there were 59,000 people in this data set. The absolute difference is also small. Small enough that the effect might be attributable to something secondary, such as sauna users consuming more water in recovery and being more hydrated. Heart rate has a relationship with hydration status.

amazingamazing 6mo ago

N=256

iwontberude 6mo ago

Website doesn’t load, it times out. Anyone have tl;dr?

kyriakosel 6mo ago
it works for me - what browser are you using?
- cpncrunch 6mo ago
  Its a cloudflare gateway timeout, so not working for anyone on any browser right now. Seems like a contradiction if cloudflare cant cache what is presumably a static site.
  - kyriakosel 6mo ago
    indeed - fixed now, let me know if you can see it!
    - cpncrunch 6mo ago
      Yes working now.
      - kyriakosel 6mo ago
        great

gcanyon 6mo ago

N=1, but I started rowing (indoor, on an erg) an hour a day -- not hard, generally 120-140 bpm -- every day starting February 28, after rowing inconsistently for a year or more before that. My resting (not sleep) pulse has dropped by 10% over the past ~7 weeks, from 60 to 54.

PaulDavisThe1st 6mo ago
General advice: citing absolute HR numbers is pretty meaningless for a broad audience, because they are not intepretable. Express them as percentages of your current max HR to be meaningful to others.
- gcanyon 6mo ago
  As I said, N=1 so the post was meaningless before I said another word :-) For your benefit: my max is somewhere around 175, maybe 180, which is high for my age. I'm also unusual in that even my max heart rate doesn't lead to lactic acid buildup, for what it's worth.

strangescript 6mo ago

Anecdotal, of course, but the biggest change I ever made in my life was right before bed: take a screaming hot shower with dim lighting. I'd say 95% of the time, I get in bed and just pass out and have no real memory of time passing before falling asleep.

Arch485 6mo ago
Increasing skin temperature is known to induce sleep (can't find a source currently, sorry). Something about your skin being warmer allowing your body to cool more effectively, I think. So a hot shower before bed is actually great for sleep, because you get the increased skin temp, relaxed muscles from the warm water, and general relaxation because showers are (for many people) relaxing.
- something765478 6mo ago
  That's funny, I find it much easier to fall asleep in a cold environment. Then again, I also like to use a heavy blanket, so maybe it's the weight more than the cold that's helping me.
  - WastedCucumber 6mo ago
    I think that's also consistent with the idea behind a hot shower. The shower doesn't help by increasing your body temperature, in fact it does the opposite. The hot shower induces the body to try to cool down, so near-skin blood vessels swell, and that dumps heat into the cold air, which reduces your core temperature, and a reduced core temperature helps you fall asleep. I think where I read about this was Why We Sleep from Matthew Walker. But he suggests just washing your face with warm water, as opposed to a shower.
- pawelduda 6mo ago
  Hot shower heats up your body, which causes it to direct blood away from the core to cool it down so it doesn't overheat. Dropping core temp triggers the brain to ramp up melatonin production. Or so I heard. Conversely, when the temperature drops, your body directs blood away from your hands and legs because core has higher priority for survival

SCdF 6mo ago

Not to be glib, but being dead lowers your night time heart rate more then exercise as well. Is having a lower night time heart rate the core goal of exercise? Is it even a goal at all? Or is it just an indicator of other goals being reached? I'm genuinely curious, I wasn't aware that the number mattered, more than what that number actually represents.

SJMG 6mo ago
It's just another measure. It's not ceteris paribus better to have a lower one. From the author, "Strongest hypothesis: elevated parasympathetic tone from the post-sauna cooling phase carries into sleep" AKA, they use it as a proxy to infer a deeper state of rest and improved recovery state. Says nothing about the fatigue generated from using a sauna.
nonameiguess 6mo ago
No, immediately lowering heart rate isn't a goal of exercise. The reason it's a meaningful measure at all is because a lower resting heart rate, not overnight in response to a stimulus, but a permanently lower resting heart rate, is a sign that your overall cardiorespiratory system has become more efficient in terms of how much blood it can deliver per beat, how much oxygen it can deliver per unit of blood, and how much energy can be generated per unit of oxygen in your mitochondria. When those efficiencies improve, fewer beats per minute results in the same level of work done in your cells. Thus, resting heart acts as a proxy measure of aerobic fitness, not a goal in and of itself. All of those are long-term adaptations. Conversely, there are many ways to acutely lower heart rate that are clearly not healthy. Death, obviously, but taking opioids or many other kinds of depressants, not moving ever, sleeping 23 hours a day, will all lower your average heart rate immediately without making you fitter or healthier.
asdfman123 6mo ago
The goal is improving cardiovascular fitness, and a low heart rate means your cardiovascular system is operating efficiently.

shevy-java 6mo ago

Well ... Finland life expectancy for 2023 was 81.69. Norway life expectancy for 2025 was 83.23. Japan life expectancy for 2025 was 85.27. Sumo wrestlers in Japan have a life expectancy between 60-65 years or so - significantly lower than the other japanese. I am not saying that sauna has no positive effect at all, but I would reason that the number one risk factor is ... weight. And I'd also still say that exercise is correlated here, if only secondary, e. g. you may be able to maintain better bodily functions if you exercise, if you can avoid injury. I do not think that going into the sauna rather than e. g. light running for 5 to 10 minutes or so, is anywhere near on the same level.

chasebank 6mo ago
News at 9, shorter people on average live longer than taller people...
- movie_fan25 6mo ago
  Unless you are from Norway or Finland, evidently.

dukeofdoom 6mo ago

Seems to me what we now know about neural networks, we should maybe weighted sum of inputs, that fire off the desired output. The human body/brain process all kinds of stimulus at once, and might only react to a combination of inputs.

YmiYugy 6mo ago

I know that for myself exercise increases my resting heart rate in the short term. It only decreases after a day or two, sometimes more depending on how fatigued I am. I thought that was common, with recovery times obviously decreasing the fitter ones gets.

storus 6mo ago

Can anyone suggest why after covid I can't do Finnish sauna anymore? Prior to that I used to do 1-2x a week a sequence of 5x(10 minutes in sauna + 5 minutes cold water immersion + 10 minutes rest) which was absolutely great for both stress reduction and blood flow. Now if I do 5 minutes in sauna I feel like my skin was burning and I am about to die, and I need to recover for 1 hour from that to be able to just walk away from sauna.

mcv 6mo ago
No idea. How hot is and was your sauna? Is it possible that it's hotter than it used to be? Maybe try one that's slightly less hot? I've got the opposite problem: saunas don't seem to be able to make me sweat anymore, so I'm looking for the hottest saunas I can find.
- storus 6mo ago
  The usual 95"C, nothing extraordinary. Sweating after covid got impaired, I might have some thermoregulation issue.
  - mcv 6mo ago
    95 is pretty hot. At commercial spas I see them start at 70, and rarely above 90.
    - storus 6mo ago
      95 is normal where I live for Finnish saunas. Then there are other types of saunas that start lower, but Finnish are always around 95.
      - jampekka 6mo ago
        95 is high for Finnish saunas in Finland at least. Public saunas are very rarely so hot here, and few like it that hot. Edit: to put it into some numbers, per one study[1] Finnish sauna sessions were on average at 75.9°C with SD 9.9°C. If we assume normal distribution, that means that more than 97 % of sauna sessions are at < 95°C. [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6262976/ https://pmc.ncbi.nlm.nih.gov/articles/PMC6262976/

nickburns 6mo ago

Why is this quackery front page?

redeux 6mo ago

I didn’t see a reference to the amount of time in the sauna required to receive this effect. Was that measured as part of this research?

eggy 6mo ago

A delta of 3 bpm on sauna days corresponds to around 4% delta if the baseline is 72 bpm. I've gone from a resting heart rate over a 7-day average of 64 bpm to 58 bpm by jumping 15 min. of rope a day, 4 times a week. I've lost weight, body fat, and I feel like my body is more efficient with corresponding lower heart rates throughout my active day. I like saunas for recovery and aches, they put me in a relaxed state after, and I believe the dilation is flushing my system. Like anything else, moderation. Perhaps I will add sauna to my weekly routine 1x per week or less.

asdfman123 6mo ago
PSA: if you like saunas but don't have easy access to one, those IR sauna bags you can buy online work great. Some people find it gross to basically sweat inside a powered sleeping bag, but if you don't mind that you can get the same effects of a sauna while lying on your (covered) couch and watching YouTube.
- sd9 6mo ago
  Wow, they look really quite dangerous. I wouldn’t want to pass out in one. Yeah you can pass out in a sauna too, but it feels easier to lurch for the door than to fight with a sleeping bag.
  - asdfman123 6mo ago
    There's a timer shutoff. I know I can sit in mine for the full hour at the highest setting, so it's not anything my body can't handle. You can set it for less time at a lower heat setting, too.
jrussino 6mo ago
> I've gone from a resting heart rate over a 7-day average of 64 bpm to 58 bpm by jumping 15 min. of rope a day, 4 times a week. Over how long of a time period?
- eggy 5mo ago

chris_va 6mo ago

This would not pass peer review for a journal as written. Maybe the conclusion is correct, or maybe not, but as written the methodology is under specified, statistics are not supported, and there too many confounders not addressed. One should not take anything from this without a better write up. Just misunderstanding what n= means is a huge flag. Since the author is here, I have to ask: Why a blog post and not an actual paper? Why spray this onto the internet without validating the work? Or, conversely, why not caveat the work as exploratory data science?

smm11 6mo ago

I feel better after sitting in a steam room two or three times a week. That's proof enough for me.

vitto_gioda 6mo ago

I also recommend reading about the effects on microplastics studied by Blueprint: https://cptsd.sites.umassd.edu/bryan-johnson-and-microplastics-reduced-plastics-by-93/ https://cptsd.sites.umassd.edu/bryan-johnson-and-microplasti...

MyHonestOpinon 6mo ago

I try to do 180 minutes a week of cardio. Mostly Zone 2. Biking, elliptical, tKD. But once in a while my legs feel too tired, so I complete my weekly minutes going to the steam room. It makes sense to me since it raises your heart rate. Also, my samsung watch can measure stress (whatever it means). It always shows the very, very minimal stress for me. The only time that I have been stressed was the day that I spent a bit too much on the steam room.

asdfman123 6mo ago
FWIW you should probably be doing some max intensity, or at least high intensity cardio. Zone 2 is great but the best health outcomes are from people who do high intensity exercise interspersed with zone 2 exercise.
- PaulDavisThe1st 6mo ago
  This is contested by a significant number of contemporary running coaches (see, for example "Training for Uphill Athletes" by Steve Johnson or any of the life work of Phil Maffetone. HIIT is quite effective at something; it's not clear that it is effective at all possible exercise goals (including, but not limited to, endurance running). Johnson in particular says that unless you've already narrowed the gap between your "first" and "second" (anaerobic) threshold to 5%, HIIT really doesn't make much sense because you're "aerobically challenged" and need to work on that first, which he believes (with significant evidence) is best done almost entirely in zone 2. He also notes that someone like Eliud Kipchoge can spend 2 hours running 4:30 min/mile pace, so that is clearly within his aerobic range, but that Kipchoge would never and should never spend much time training at that pace because of the load it would put on his system. So the zones that are used for training purposes depend significantly on the current fitness level of the athlete. I have used HIIT effectively to get myself out of certain fitness/training "ruts", but I think that the zone 2 folks have somevery cogent and coherent observations and advice.
  - mchusma 6mo ago
    I think one issue I have with Zone 2 proponents is that it makes sense that if you can do a lot more stuff at Zone 2 than you can at less. For most endurance athletes, the volume of running beats everything else in terms of efficacy. However, most of us don't have unlimited time. For example, if I do a week of 3x30 minute swssions at Zone 2, my fitness is going to plummet. But if I do one at Zone 2, one at tempo, and one set of intervals, I'm at least maintaining fitness. Would 5 hours at zone 2 be better? Absolutely. But I dont always have the time.

atum47 6mo ago

Should I assume a steam room has the same effect? I prefer it over sauna

dtran 6mo ago
Potentially, but likely much less effective and less studied, and you likely need longer sessions for effective dosage. Most of the studies I've seen on improvements in blood plasma volume from passive heat are usually done with sessions in saunas with temperatures > 150 degrees F (60 C). Steam rooms usually only get up to 120F (~49C) even though the humidity probably makes it feel warmer. Copying and pasting some of my reply to another comment above
- PaulDavisThe1st 6mo ago
  Sweating is one the main triggers for an increase in blood plasma volume, and the humidity level of a steam room causes vastly higher rates of sweating than most saunas do. You can lose significant body heat by sweating in a dry environment, but much less in high humidity. Consequently, your body needs to sweat much more rapidly even though the absolute temperature may be lower.
  - dtran 6mo ago
    To my understanding, while sweating is important to heat adaptation and blood plasma volume adaptations, thermal load and cardiovascular strain are likely bigger factors (and more important for the health benefits mentioned in this study). Overall thermal load is still higher in a hotter dry sauna than in a steam room
    - PaulDavisThe1st 6mo ago
      That's not my understanding, but my understanding is somehwere between 3rd and 6th hand, so it's likely not worth much.
kyriakosel 6mo ago
that would be interesting to study - let me follow up on this

kp988 6mo ago

I use the sauna every day and highly recommend it to everyone, it's great for your health and for stress

michaelteter 6mo ago

My anecdotal experience: TLDR: regular sauna seems to have no effect on my resting HR. Extended high HR cardio definitely does. I became a huge fan of sauna time (15-20 minutes at approx 175F/80C... I would prefer a bit warmer, but I had no control). It was like shower time, or meditation time (which I never took time for). Great thinking time. I'd use it after a workout, but I would also use it on days without a workout. I've been tracking some stats via my Garmin watch for a few years, and I've identified some patterns - particularly regarding resting HR. The most significant reducer of resting heart rate for me is running (5k). Periods where my training includes regular 5k runs cause my resting HR to drop by 5-8 bpm. Most of my training is resistance, although in the last 6 months I've added in a lot more cardio. Stairs and rowing do not seem to noticeably reduce my resting HR. Running definitely does. But to be fair, maybe it's not the running but rather the active HR I'm sustaining. Despite trying to stay in the aerobic zone, running always pushes me to zones 4 and 5. So 50% of my 30 minutes of exercise will be in my max zone. With stairs or rowing, I can keep my HR in aerobic and threshold. Some stats: When I'm off my fitness routine, living life as a typical person, my resting HR is 65. When I'm on a resistance fitness routine, my resting HR is 58. When I'm also running, the rHR is 51. If I eat a heavy meal too close to bedtime, my rHR is +15. If I drink a lot of alcohol before sleeping, rHR can be +20! Food + alcohol = WTF. Probably not good.

manapause 6mo ago

As an amateur sauna evangelist, I can say my experience sauna usage 1-2 times a week has greatly improved my life and quality of sleep!

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theshrike79 6mo ago

Correct me if I'm wrong, but I thought HRV (Heart Rate Variability) is a bigger positive correlation for health than low heart rate?