Most people assume cold therapy requires several minutes of teeth-gritted endurance. The question of how long to stay in an ice bath dominates every beginner conversation, and the answers land somewhere between two and fifteen minutes, depending on who you ask.
The largest cold therapy trial ever conducted found something different.
In a 2016 randomised controlled trial published in PLoS ONE, Dr Geert A. Buijze and his research team recruited 3,018 participants across the Netherlands and split them into groups that finished their daily hot shower with a blast of cold water lasting 30, 60, or 90 seconds. A control group showered normally. The study ran for 30 consecutive days, followed by 60 days of monitoring.
All three cold-water groups showed a 29% reduction in sickness absence from work compared to the control. The difference between 30 seconds and 90 seconds? Statistically nonexistent. The p-value was 0.98, as close to identical as research gets.
“Duration didn’t matter,” Buijze confirmed. “The reduction in sick days was the same across the 30-, 60-, and 90-second groups.”
What Buijze actually found
The study’s scale alone makes it unusual. Most cold therapy research involves a few dozen participants. Buijze had over three thousand, properly randomised, with a clear control group and a measurable real-world outcome: days absent from work due to illness. Not a subjective wellness score. Whether people showed up.
Of the participants assigned to a cold-water group, 79% completed all 30 days. More telling: 64% voluntarily continued cold showers after the study ended, even though nobody asked them to.
The 29% reduction was consistent across all three cold-water durations. Whether you stood under cold water for half a minute or a minute and a half, you were roughly a third less likely to call in sick. That kind of dose-equivalence is unusual in health interventions — you’d expect a dose-response curve, more exposure yielding more benefit. Instead, the response appeared to plateau at the lowest dose tested.
People didn’t get sick less. They showed up more.
Buijze’s team tracked two separate outcomes: sickness absence (days off work because of illness) and illness days (the number of days participants actually reported feeling unwell). The cold-water groups took significantly fewer sick days, but they did not report significantly fewer illness days. They still caught colds and still felt rough. They just showed up anyway.
Cold showers didn’t turn anyone into someone who never gets sick. What they appeared to do, across all three durations, was change how people responded to being sick. The study’s authors described the effect as comparable to that of regular physical activity on sickness absence; combining cold showers with exercise produced a 54% reduction, nearly double the cold-only effect.
The implication reframes what cold therapy is doing for most people. It’s not an immune shield. It’s a resilience practice. The cold trains your ability to function under discomfort, and that training appears to carry over into days when you’re under the weather but capable of getting on with things. If you’ve been drawn to cold exposure because someone told you it “boosts your immune system,” the honest answer is more interesting: it seems to boost your capacity to tolerate feeling bad.
A 2025 systematic review published in PLoS ONE, pooling 11 studies and over 3,100 participants, found significant stress reduction and improvements in sleep and quality of life following cold water interventions. But the review also noted that the evidence base remains constrained by few large RCTs. Buijze’s study is still, by a wide margin, the biggest and cleanest trial available.
One caveat: the quality-of-life improvements in the Buijze study faded by the 90-day mark. The sickness-absence effect persisted across the full follow-up period, suggesting that the behavioural shift was more durable than the subjective wellness boost.
Cold showers are not ice baths
Buijze’s study used cold showers, not ice baths. The participants ended their warm shower with a cold blast and did not sit in water at 2°C.
That distinction matters. As clinical researchers at Atria have explained, cold showers “do not induce the same intense thermal stress or sympathetic activation” as full-body immersion. Under a shower, only part of your body contacts cold water at any given moment. In an ice bath, water surrounds you completely, the thermal load is heavier, the nervous system response more pronounced, the metabolic effects different.
So can you apply the Buijze finding directly to an ice bath? Not precisely. But the mechanism is shared: acute cold stress triggering a systemic response. Cold shower vs ice bath differences operate at a lower intensity; full immersion turns up the dial. Both expose the body to a brief, controlled thermal challenge, and both appear to produce meaningful health effects.
The practical way to think about it: cold showers are a legitimate starting point, and if 30 seconds of cold shower produced the same outcome as 90 seconds in the largest trial available, the entry barrier for cold exposure is genuinely low. Full immersion may offer more potent effects. Susanna Søberg, whose research was published in Cell Reports Medicine, has observed that immersion is “more potent to activate metabolism” because the cold contacts the entire body simultaneously. But that’s a next step, not a prerequisite.
A cold shower in Edinburgh in January is a very different thermal experience from a cold shower in Bangkok in August. Tap water temperature varies enormously by geography and season, which means the actual cold dose from a “cold shower” is less standardised than it sounds. Controlled immersion, where you set the ice bath temperature precisely, removes that variable.
Why most duration guides say much longer
If you’ve searched for how long you should stay in an ice bath before, you’ve probably seen recommendations in the range of 10 to 15 minutes. Those numbers come from a different body of evidence addressing a different question.
Athletic recovery research on delayed-onset muscle soreness and post-training inflammation typically uses longer immersion at moderately cold temperatures (10–15°C) for 8 to 15 minutes, and those cold plunge protocols have been studied primarily in trained athletes.
The problem is that those numbers have migrated into general wellness advice, where they serve as the default answer to a question they were never meant to address. Someone who wants to know “how long should I sit in cold water for my health?” is not the same person as a rugby player managing quad soreness after a double session. Conflating the two creates an unnecessarily intimidating entry point, so a first-timer reads “start with 2 minutes and work up to 10” and delays starting indefinitely.
The Buijze study matters because it measured something closer to what most people want from cold therapy: a general health benefit from a sustainable daily habit. And it found that the minimum effective dose, at least for cold shower benefits, was the lowest dose they tested.
How to actually start
Søberg’s research complements Buijze’s per-session finding with a weekly framework: 11 minutes of cold exposure per week, split across two or three sessions, is sufficient for measurable health benefits. Combining the two gives you a practical map.
Phase one: cold showers. Finish your regular shower with 30 seconds of the coldest water available. Do this every morning for 30 days. If 30 seconds feels manageable after a week, extend to 60 — not because you need to, but because you want to. The Buijze data says the extra time makes no measurable difference, but many people find the practice becomes its own reward.
Phase two: deliberate immersion. Once cold showers feel routine, consider a cold plunge. Start with 1 to 2 minutes at 10–15°C, building toward Søberg’s 11-minute weekly total across a month. The transition is significant, because full-body cold load feels substantially different from a shower stream. Having a purpose-built plunge or ice bath makes that step feel like a natural progression rather than an ordeal, and it’s also why well-run spas and recovery spaces don’t push endurance on newcomers.
The adherence data reinforces this. In Buijze’s study, one in five participants dropped out before completing 30 days, and practitioners and cold therapy providers see similar patterns: the first month is where the habit either takes hold or fails. But those who stayed past the initial resistance kept going, and nearly two-thirds chose to continue voluntarily. The habit sticks when the ask is modest enough to survive the early discomfort.
If you’re moving into full immersion for the first time, experienced practitioners recommend starting with guidance — not because short immersion is dangerous for a healthy person, but because having someone who knows what a normal response looks like removes the uncertainty that makes people quit.
The real benefit isn’t endurance
Cold therapy has acquired a culture of toughness that the evidence doesn’t support. The 10-minute ice bath, the gasping social media plunge, the implication that more suffering equals more benefit — none of it holds up against the largest dataset available. Thirty seconds of cold water, applied consistently, produced the same measurable outcome as three times that duration.
What it produced wasn’t immunity. It was the quieter, more useful thing: the people in Buijze’s study still got sick. They still felt bad. But they showed up, functioned, and carried on. That capacity may be the most undervalued outcome cold therapy offers.
The question was never how often should you ice bath. It was about what those seconds train you to do with everything that comes after.
