Founders plunge into ice baths and sit in scorching saunas. Here is what the research backs, what it costs them, and the version you can do tonight.
This in-depth guide covers everything you need to know about cold plunge benefits and sauna: what the rich get for $18k. Based on verified income data and real-world case studies from our database of 138 side hustle tactics.
The best-supported cold plunge benefits are modest: lower reported stress about 12 hours later, and possibly better sleep and quality of life, from a small set of trials. The sauna has stronger long-term data, with a 20-year Finnish study linking four to seven sessions a week to fewer cardiac deaths, though it only shows an association. A $10,000 home plunge buys convenience, while a cold shower and a $29 bathhouse pass give you most of what the research measured.
Who plunges and who sweats: the habit as the rich describe it
Picture a man waking up and lowering himself into a pool of cold water to start the day. That scene comes from Tony Robbins himself. On his own site he writes: "Every morning, I wake up and plunge into a 57-degree pool of water."
Jack Dorsey's version was harsher. In 2019 he described it on Ben Greenfield's podcast, and CNBC wrote it up: 15 minutes in a barrel sauna set at 220 degrees, then three minutes in a 37 degree ice bath, three rounds, finishing with one minute in the ice. He later bought a small near-infrared sauna tent. His reason had nothing to do with blood markers. "Nothing has given me more mental confidence than being able to go straight from room temperature into the cold," he said in the same CNBC piece.
Bryan Johnson goes the other way and keeps it hot. His published protocol lists a dry sauna at 175°F, 20 minute sessions, daily, seven days a week, and the type line names the brand: "Dry sauna (Plunge)." The rest of his day belongs in our Bryan Johnson Blueprint breakdown.
Then there is the podcast layer. Neuroscientist and podcaster Andrew Huberman told his newsletter readers in May 2022: "Consider doing deliberate cold exposure for 11 minutes per week TOTAL," split into two to four sessions of one to five minutes. Peter Attia's wider training framework sits in the Peter Attia protocol post.
Robbins talks about energy, Dorsey about confidence, Johnson about his heart, Huberman about dopamine and adrenaline. Four promises from two simple things: getting very cold and getting very hot.
Which of those four promises is the one you actually want?
What the sauna research shows
The study that made the sauna famous is Finnish. Researchers followed 2,315 middle-aged men from Eastern Finland for a median of 20.7 years, as part of the Kuopio Ischemic Heart Disease Risk Factor Study, and published the results in JAMA Internal Medicine in 2015. Laukkanen and colleagues asked one simple question at the start: how often do you take a sauna, and for how long?
Then they counted deaths. Here is what they reported for all-cause mortality, the raw share of each group that died during follow-up:
| Sauna sessions per week | Men in group | Died from any cause | Sudden cardiac deaths |
|---|
| 1 | 601 | 49.1% | 10.1% |
| 2 to 3 | 1,513 | 37.8% | 7.8% |
| 4 to 7 | 201 | 30.8% | 5.0% |
Source: Laukkanen et al., JAMA Internal Medicine, 2015.
After adjusting for heart risk factors, men who used the sauna four to seven times a week had a hazard ratio for sudden cardiac death of 0.37 compared with once a week men. Session length mattered too. Sessions longer than 19 minutes were linked to a lower risk of sudden cardiac death than sessions under 11 minutes, with a hazard ratio of 0.48.
The same cohort produced a second headline. In Age and Ageing in 2017, the team reported that men taking four to seven saunas a week had a hazard ratio for dementia of 0.34 compared with once a week users.
A 2018 review in Mayo Clinic Proceedings pulled the sauna literature together and listed the proposed reasons: better blood vessel function, lower arterial stiffness, lower blood pressure and shifts in the nervous system.
How much weight these numbers can carry
Read the table again with one question in mind: who takes a sauna four to seven times a week in 1980s eastern Finland? Possibly men who were healthier to begin with. The study adjusted for known risk factors, but an observational study cannot rule out that healthier men simply sauna more. The 4 to 7 group was also small, just 201 men.
The cohort was all men, aged 42 to 60, using traditional Finnish saunas. It tells you little about women, about infrared cabins, or about a 30 year old starting today. The authors themselves wrote that further studies are needed to establish the mechanism.
So the honest reading is this: frequent sauna use in this group went with better heart outcomes, and the pattern held across sudden cardiac death, heart disease deaths and deaths from any cause. It is encouraging. It is also unproven as cause and effect.
Would you change your week based on an association, or wait for a trial that may never be run?
What the cold plunge research shows
The cold side has more trials and weaker long-term data. The best recent summary is a 2025 systematic review and meta-analysis in PLOS One that looked at randomised trials of cold water immersion in healthy adults. It included 11 studies with 3,177 participants, using baths or showers at 7°C to 15°C (about 45°F to 59°F) for 30 seconds up to two hours.
What it found, in plain words:
- Stress: lower reported stress 12 hours after immersion. No significant effect immediately, at one hour, at 24 hours or at 48 hours.
- Inflammation: inflammation markers went up right after the cold and one hour later. The authors read this as an acute inflammatory response.
- Immunity: no measurable change in immune markers in the short term.
- Sleep and quality of life: improvements reported.
- Mood: no improvement.
The authors were blunt about the limits: few randomised trials, small samples and a lack of diversity in the people studied. One more detail: a single cold shower trial supplied 3,018 of the 3,177 participants, so the pooled picture leans heavily on it.
That inflammation result is worth sitting with for a moment. Many plunge fans say the cold reduces inflammation. In this review the short-term effect ran the other way.
The cold shower trial with 3,018 people
The biggest single study in that review is a Dutch trial. In 2015, researchers randomised 3,018 adults to end their normal hot shower with 30, 60 or 90 seconds of cold water for 30 days, or to keep showering as usual. Published in PLOS One in 2016, it found a 29% reduction in self-reported sickness absence from work in the cold groups. It found no difference in the number of days people were actually ill. No related serious adverse events were reported.
So the cold shower group got sick just as often but called in sick less. The study cannot tell you why.
Think about what that trial used: an ordinary shower handle and 30 seconds. No tub, no chiller, no app.
Where the dopamine number comes from
You may have heard that cold water raises dopamine by 250%. That figure is real, and it comes from a 2000 study in the European Journal of Applied Physiology. Young men sat in water up to the neck for one hour. At 14°C (about 57°F), plasma noradrenaline rose by 530% and dopamine by 250%, and metabolic rate rose by 350%.
Two details get lost in the retelling. The exposure lasted an hour, far longer than a three minute plunge. And it measured hormones in the blood, a different thing from lasting change in mood or motivation. Huberman's newsletter describes the dopamine study it relies on as people in "cool (60°F) water for about an hour."
The winter swimmers behind the 11 minute rule
The 11 minute figure matches a small study of Scandinavian winter swimmers published in Cell Reports Medicine in 2021 by Susanna Søberg and colleagues. It compared 8 experienced winter swimmers with 8 controls. The swimmers did cold dips and hot saunas two to three times a week, and in the study's own table they averaged 11 minutes a week in cold water and 57 minutes a week in the sauna.
The swimmers produced more heat in response to cold. That was the finding. It did not test whether 11 minutes a week makes anyone healthier, leaner or happier. The number describes what these men already did, and it became a dose because it was easy to remember.
Does knowing the 11 minutes came from eight people change how seriously you take it?
Cold after lifting: the muscle-growth catch
This is the finding most gym-goers miss, and it matters if you train for strength or size.
In a 2015 study in The Journal of Physiology, 21 active men lifted weights twice a week for 12 weeks. After each session, half sat in cold water for 10 minutes and half did active recovery instead. Strength and muscle mass rose more in the active recovery group. Type II muscle fibre size grew by 17% in that group and did not grow significantly in the cold group. The authors concluded that regular cold water immersion after training "should be reconsidered."
A 2024 meta-analysis in the European Journal of Sport Science, titled "Throwing cold water on muscle growth," pooled 8 studies and reached the same direction: plunging right after resistance training "may attenuate hypertrophic changes." The authors asked readers to interpret the result with some caution, because the studies were few and small.
Huberman's own newsletter carries the same warning, though it exempts cold showers. It says cold water immersion "can limit some of the gains in hypertrophy, strength or endurance if done in the 4 hours or so after training" and suggests waiting "6 to 8 or more hours," or doing the cold before training.
An athlete who needs to feel fresh for tomorrow's game may still choose the ice bath. If your goal is to build muscle over months, put the cold at a different time of day. Strength training itself has some of the best evidence in this whole series, and coaches who teach it well can earn from it, as our online fitness coaching guide shows.
When do you train, and when would a plunge fit if you kept it away from that window?
Contrast therapy: hot, cold, repeat
Contrast therapy means switching between heat and cold, the way Dorsey did with three rounds of sauna and ice. Bathhouses sell it as a circuit. Bathhouse in New York suggests at least 15 minutes in the sauna and 1 to 3 minutes in the cold plunge.
The research on contrast as a package is thin. The Søberg winter swimmers did both, and their study is the closest thing to a test of the routine, with eight people and one physiological outcome. Huberman's newsletter adds a simple rule he credits to Søberg: "End With Cold," and let your body reheat on its own instead of towelling off and huddling.
Most people end up doing contrast anyway, because the sauna makes the cold bearable. Enjoyment matters: the Finnish data is about doing something four times a week for twenty years.
The risks: cold shock and heat strain
Both practices put real load on the heart. That is part of why they might help, and it is why they can hurt.
Cold shock. Sudden entry into cold water sets off what physiologists call the cold shock response, which drives the heart rate up through the sympathetic nervous system. A 2012 review in The Journal of Physiology describes how cold water submersion "can induce a high incidence of cardiac arrhythmias in healthy volunteers." Putting your face under while holding your breath triggers the opposite reflex, the diving response, which slows the heart. The authors propose that firing both at once may explain some sudden deaths in cold water that were wrongly blamed on drowning or hypothermia. A broad review in Experimental Physiology lists cold water immersion as a precursor to drowning and cardiac arrest, and says that some claimed benefits "remain at the level of anecdotal speculation."
Even in the 2000 dopamine study, 14°C water raised heart rate and systolic and diastolic blood pressure. Huberman's newsletter warns that "cold shock is possible," to start warmer, to never enter a dangerous body of water, and never to hyperventilate on purpose before or during immersion.
Heat strain. Harvard Health advises staying in no more than 15 to 20 minutes, drinking two to four glasses of cool water afterwards, and avoiding alcohol and medications that impair sweating before and after. It notes that blood pressure can rise in some people and fall in others, and says people with uncontrolled high blood pressure or heart disease should check with their doctors first.
A plain note: this is general information, and your own doctor knows your heart better than any article. If you have heart disease, high blood pressure, a heart rhythm problem, Raynaud's, are pregnant, or take medication that affects blood pressure or sweating, talk to your doctor before you start either practice. Never plunge alone in open water, never combine a sauna with alcohol, and get out if you feel dizzy or your chest feels wrong.
What the cold plunge costs, from a $0 shower to a $10,000 tub
Here is what each route costs as of October 2026, from the sellers' own pages. Plunge figures are list prices; its pages also showed sales, such as $6,790 for The Plunge and $7,990 for the All-In.
| Setup | Price as of 2026 | What it includes |
|---|
| Cold shower | $0 | 30 to 90 seconds of cold at the end of a shower, the dose in the Dutch trial |
| Bathhouse day pass, NYC or Philadelphia | from $29 to $39 | Saunas, cold plunges at 45°F to 50°F, steam rooms |
| Plunge Air, tub only | $1,190 | Insulated inflatable tub; the chiller is an optional extra |
| Ice Barrel 300 with chiller | $5,149.98 | Upright barrel plus a chiller to hold the temperature |
| Plunge Original tub | from $8,490 | Cools to as low as 37°F with its Pro Chiller |
| Plunge All-In | from $9,990 | Plug-in tub with chiller, ozone sanitation and an app |
And the heat side:
| Setup | Price as of 2026 | What it includes |
|---|
| Plunge Infrared Sauna | $7,690 | Infrared cabin |
| Almost Heaven Salem barrel sauna kit | $5,484 | Two-person traditional sauna kit with a 6kW heater |
| Plunge The Sauna | from $12,990 | Cedar sauna that heats up to 230°F, the brand on Bryan Johnson's protocol |
| Plunge All-In plus The Sauna bundle | $18,030 | The full home contrast setup |
Notice the gap. A home setup that copies Johnson's sauna and adds a chilled plunge runs about $18,000 before installation, electricity and space. A bathhouse that has both, at temperatures inside the range the research used, starts at $29 a visit. At $39 a visit you would need about 460 visits before the $18,030 bundle pays for itself on price alone, which is more than four years of twice-weekly trips.
Also notice that the cheapest option is the one with the biggest trial behind it. The Dutch cold shower study supplied 3,018 of the 3,177 people in the 2025 review.
What would $18,000 do for you if it went somewhere other than your backyard?
Plunge and sauna claims to discount
Several claims around plunges and saunas go further than the studies.
"Cold plunges reduce inflammation." In the 2025 meta-analysis, inflammation markers rose immediately and at one hour after cold water. The healthy-adult data in that review does not show a general anti-inflammatory effect.
"Plunging after the gym speeds up your gains." The trials point the other way for muscle size and possibly strength.
"Saunas detox your body." The CNBC Dorsey piece itself notes that sweat is not the body's primary tool for removing toxins. None of the studies above measured toxin removal.
"Colder and longer is better." None of the trials above show a dose response that rewards going near freezing. The Dutch trial used ordinary tap cold for 30 to 90 seconds. The bathhouse plunges sit at 45°F to 50°F. Colder water raises the cold shock risk and does not come with extra proven benefit.
"Infrared saunas give you the Finnish results." The Finnish cohort used traditional hot saunas. Infrared cabins run cooler (Bathhouse lists its infrared sauna at 135°F in Flatiron against 185°F for its dry sauna). They may help, but the mortality data was not collected on them.
"A 250% dopamine boost from a quick dip." That number came from an hour in 14°C water, measured in the blood.
"Cold exposure melts fat." The winter swimmer study found more heat production in response to cold in eight men. It did not measure weight loss, and no trial in this post shows a plunge habit making people leaner.
Which of these had you already heard as fact?
What the rich are really buying
Look again at the people at the start. Robbins has a 57 degree pool waiting every morning. Dorsey had his own barrel sauna and ice bath, then added an infrared tent. Johnson runs a Plunge-brand dry sauna on a fixed daily slot, from a maker whose traditional sauna lists from $12,990. What their money buys is friction removed: the water is always cold, the sauna is always hot, and it sits twenty steps from the bed.
That convenience is the part you can replace with planning. The stimulus itself, a few minutes of real cold and fifteen to twenty minutes of real heat, is open to anyone with a shower and a gym or bathhouse nearby.
There is one more thing their habits share with a good money plan: they are boring and repeated. Johnson's sauna is daily. The Finnish men who did best went four or more times a week for decades. The same shape shows up in index investing, where the result comes from a plain habit repeated for years. If you are tempted by the $10,000 tub, ask how often you would still use it in year three.
Your hot and cold plan this week
You can run a fair copy of the rich person's routine for close to nothing. Here is a simple week, built from the doses in the studies above.
- Cold, daily, free. End your normal shower with 30 to 90 seconds of cold water, the range in the 3,018 person Dutch trial. Breathe slowly through the first gasp. Stay standing, keep your face out if you feel lightheaded, and stop if you feel unwell.
- Heat, two or three times, cheap. If your gym has a sauna, sit for 15 to 20 minutes after a workout, inside the Harvard Health limit. Drink water afterwards. Skip it after alcohol.
- Contrast, once, $29 to $39. If you live near a bathhouse, book one day pass and try the circuit the way it was designed: a sauna round, one to three minutes in the plunge, repeat.
- Keep cold away from lifting. On strength days, put the cold shower in the morning and train in the evening, or the other way around, so they sit more than six hours apart.
- Track one thing. Pick sleep quality or how stressed you feel the next morning, the two outcomes with some support, and write a score each day. After four weeks you will know if it is worth more of your money.
If cold showers wake you up, they may also help you get out of bed for an early start. How the very rich order their mornings is in our billionaire morning routines post, and the gear they use to sleep is in the billionaire sleep stack.
And if the routine makes you want a home sauna someday, set it as a goal you fund from new income. A side hustle you can start with zero dollars can pay for the bathhouse passes first, and the barrel sauna later, without touching savings.
So, tonight's shower: will you turn the handle to cold for the last thirty seconds?