Summary
Josh and Chuck from Stuff You Should Know tackle the hot-cold plunge trend in this short episode. They trace the practice back to Finnish sauna culture and explore the concept of hormetic stress, where controlled exposure to temperature extremes trains the body's stress response and immune system. The hosts note that saunas independently lower blood pressure, improve cardiovascular health, and mimic exercise, while cold plunges are anti-inflammatory and can improve mood by triggering dopamine and norepinephrine release. However, they emphasize an important caveat: while each modality has solid research behind it individually, the evidence for combining hot and cold therapy is still limited. Most existing studies have small sample sizes of young, healthy participants, and large-scale controlled trials are only now getting underway. The episode also covers real safety concerns, including cold shock response that can cause cardiac arrest, involuntary gasping underwater, and risks for anyone with cardiac conditions. They recommend using warmer cold water (around 70 degrees Fahrenheit) rather than extreme cold to get benefits with less risk, and consulting a doctor before trying contrast therapy.
Key Points
- Finnish sauna culture originated the practice of alternating between heat and cold, with "sauna" meaning "bath" in Finnish
- Hormetic stress from temperature extremes trains the body to better handle unintentional stress, improving immune function and resilience
- Saunas independently lower blood pressure, activate the cardiovascular system, mimic exercise, and help detoxify
- Cold plunges are anti-inflammatory and can release dopamine and norepinephrine, enough to short-circuit a panic attack via the diving reflex
- Research on combining hot and cold therapy is still in early stages with small sample sizes; large-scale trials are only beginning
- Cold shock response can cause rapid heart rate and blood pressure increases, posing cardiac arrest risk especially for those with heart conditions
- Water at 70 degrees Fahrenheit can provide cold plunge benefits with much less risk than the often-recommended 57 degrees
- Hot-cold contrast showers are an accessible, lower-risk alternative to dedicated plunge setups
Key Moments
Hormetic stress explained - why temperature extremes help
Josh and Chuck explain the hormetic effect, where controlled stress from temperature extremes trains the body to better respond to unintentional stress, improving the immune system and overall resilience.
"And so supposedly, according to this idea of the hormetic effect, which seems to be pretty legitimate, by just kind of slowly, little by little, stressing your body, you improve your body's stress response, your immune system, that kind of thing. And exercise is one way to do it, but also exposing it to temperature extremes, like through a sauna or a cold plunge also produces hormetic effects because they put hormetic stress on your body, too. That seems to be the basis behind health benefits from sauna-ing or cold plunging."
Cold plunge triggers diving reflex and mood boost
Josh describes how cold water exposure releases dopamine and norepinephrine, and how the diving reflex from submerging your face in ice water can short-circuit a panic attack in about 10 seconds.
"And it produces what's called the diving reflex. And it releases dopamine and norepinephrine in enough amounts that it can actually derail or short circuit a panic attack. So there is like actual legitimate benefits to each one. Like you were saying though, it's them combined that the jury is still out on, right?"
Cold shock response dangers and safety guidelines
The hosts discuss serious risks of cold plunging including cold shock response that can cause cardiac arrest, involuntary gasping if submerged, and why people with cardiac conditions should consult a doctor first.
"So depending on who you talk to, there's something called a cold shock response where you have such a rapid increase in breathing and heart rate and blood pressure that if you're not in great cardiac health, this could possibly kill you. Like you could have a cardiac arrest right there on the spot. Yeah, that's nuts, which makes sense because, I mean, it feels like you could like when you jump into a cold plunge, especially if you're already really hot. But supposedly in less than a minute, you could die in water that's 60 degrees Fahrenheit or lower."
Warmer water still works - safer contrast therapy approach
Chuck and Josh explain that water at 70 degrees Fahrenheit provides meaningful cold exposure benefits with far less risk than extreme cold, and that even a hot-to-cold shower switch can deliver some benefit.
"I mean, I'm talking like 70 degrees. Still sounds warm. That's not warm, especially if you're in like a hot tub first or a sauna first or you've exercised or something like that. It does the trick. It does everything you need to do without, or I shouldn't say without the chance of killing you, with a much less chance of killing you."
