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Oct 29, 2026

Ice swimming science: what research says about the cold plunge

In Finland, a dip in a hole cut through lake ice, avanto in Finnish, is an ordinary winter habit rather than a stunt. People who join a Finnish sauna evening often ask what the cold actually does to the body, and whether the health claims they have read online are true.

This article summarises what peer-reviewed and university research says about ice swimming science: what happens in the first minutes, how the body adapts, and which benefits are supported or still uncertain. We are a tour operator, not doctors, so we stay close to the sources listed at the end and make no medical promises.

Research shows that a plunge into very cold water triggers an immediate “cold shock” response: a gasp, fast breathing, and a sharp rise in heart rate and blood pressure, which fades within a minute or two as the skin cools. The body gets used to this response quickly with repeated exposure. Reported benefits, such as lower stress some hours later and better self-reported sleep and quality of life, come from a small number of trials, and researchers say more and better studies are needed.

At a glance

• From: 398 €
• Experience type: Sauna / culture experience
• Duration: 4 hours
• Difficulty: Easy
• Book in Advance: Cut off: 3 hours before start time
• Included: A traditional wooden heated sauna for you to use; A handmade ice- hole for the cold plunge; Instructions on how to safely use the sauna and do the cold plunge; Towels; A Tour Guide in English (other languages available on request: (Spanish, Catalan, Portuguese, french, Italian, German & Finnish. PLEASE NOTE LIMITED AVAILABILITY FOR OTHER LANGUAGES) If another language is required. Please send us an email or WhatsApp after booking.); Winter clothing (Adult & Child size), overalls, boots, gloves, socks; Local light snack and drinks; Pick-ups and drop-offs are included in the price in 10 km radius from Rovaniemi city center; Photos taken with your own device; Air conditioned car
• Cancellation: Free cancellation 24 hours before the activity. We will charge a cancellation fee of 100% if booking is cancelled less than 24 hours before the activity.
• Accessibility: Not wheelchair accessible; Not stroller accessible

The first minute: the cold shock response

The most studied part of ice swimming is the very beginning. Researchers at the University of Portsmouth, led by Professor Mike Tipton, describe cold shock as an involuntary reaction to sudden immersion in cold water. It starts with a gasp of two to three litres of air, followed by rapid breathing that is hard to control.

The good news in their findings is that the response is short-lived. As Tipton puts it, once the skin reaches the temperature of the water, “which takes about a minute or two”, the response goes away. The same research group warns that most deaths in the first minutes of accidental cold water immersion are due to cold shock, which is why a controlled, supervised entry matters so much.

Heart rate, blood pressure and noradrenaline

Finnish researchers have measured what happens in the circulation. In an article for the Finnish Society of Sport Sciences, exercise physiologist Dr Juhani Smolander summarises that in winter swimming systolic blood pressure rises by approximately 40–50 mmHg and diastolic pressure by 10–20 mmHg. Levels of the stress hormone noradrenaline rise two- to threefold after the dip, and this reaction was repeatable over three months of regular swimming.

These are large, fast changes. For a healthy person they are temporary, but they are also the reason why anyone with a heart condition or high blood pressure should speak to their own doctor before trying ice swimming.

Habituation: why the second dip feels easier

Almost everyone who tries ice swimming says the second or third dip feels different from the first. Research supports this. According to Smolander’s summary, habituation to the cold happens almost completely within the first two to three ice-swimming sessions.

A University of Portsmouth study by Clare Eglin and Mike Tipton (European Journal of Applied Physiology, 2005) tested whether cold showers could train the response. After six cold showers at 10 °C, breathing frequency in the first 30 seconds of a 10 °C immersion fell by 21%, although heart rate was not significantly reduced. Warmer showers produced no habituation.

An important caution from the Finnish work: feeling less cold does not remove the physiological risk. Getting used to the sensation is not the same as being protected.

Stress, sleep and wellbeing: what the evidence shows

The most complete recent overview is a systematic review and meta-analysis from the University of South Australia, published in PLOS One in 2025. It pooled 11 randomised controlled trials with 3,177 participants on cold-water immersion.

• Inflammation markers rose immediately and one hour after immersion, an acute response rather than a lasting change.
• Stress was significantly lower 12 hours after immersion, but not at other time points.
• Participants reported better sleep quality and quality of life, but no change in mood.
• There was no significant effect on immune measures in the pooled analysis, although one cold-shower study reported 29% less sickness absence.

In the Finnish research summarised by Smolander, sauna combined with winter swimming kept a pleasant mood for about 20 minutes longer after the activity, while objectively measured sleep quality did not change significantly.

The limits of the research

It is worth being honest about what we do not know. The South Australian authors write that the evidence base is limited by few randomised trials, small sample sizes and a lack of diversity: only one of the eleven trials included women, and six looked at a single immersion. Several studies combined cold water with recovery after exercise.

So when you read that ice swimming “boosts immunity” or “cures” anything, treat it with care. The honest summary is that cold water produces strong, short-lived physiological reactions, the body adapts quickly, and some people report feeling less stressed and sleeping better, while larger and longer studies are still needed.

Sauna and ice: the Finnish way

In Finland, ice swimming is usually part of a sauna evening rather than an activity on its own. Smolander estimates that about 150,000 Finns swim in winter regularly, typically people aged 45–55 who go two to three times a week. The rhythm is simple: warm up in the sauna, take a short dip, return to the heat, and repeat at your own pace.

The sauna makes the experience more comfortable, and the short dip is the point, not endurance. Nobody needs to stay in the water long for the experience to be real.

How this shows up on our tours

Our Private Wooden Heated Sauna and Ice Swimming experience is built around exactly this rhythm. According to the product page, it includes a traditional wooden heated sauna for your private use, a handmade ice hole for the cold plunge, instructions on how to safely use the sauna and do the cold plunge, towels, winter clothing, a light local snack and drinks, and pick-up and drop-off within a 10 km radius of Rovaniemi city centre. The experience lasts 4 hours and costs from 398 €. A hot tub can be booked as an extra (249 €).

Your guide gives instructions on how to use the sauna and do the cold plunge safely, and you decide how many dips you take. Swimsuits are optional in this private setting.

If you would rather keep the heat and skip the ice, the Private Traditional Finnish Sauna & Jacuzzi use at Aurora Hill Resort gives you a private sauna and a jacuzzi, and you can step out into the snow between rounds. In summer our Traditional Finnish Sauna Experience ends with a swim in the lake instead. You can see all our options on the sauna activities page and read more in our guide to traditional Finnish sauna experiences in Lapland.

Who should think twice

Based on the research above, we suggest speaking to your doctor before ice swimming if you have a heart condition, high blood pressure or another serious health condition. Do not go into an ice hole alone: the first minute is when cold shock is strongest. If you feel unwell, simply stay in the sauna; that is a complete Finnish sauna evening too.

Frequently asked questions

What is the cold shock response?

It is the body’s involuntary reaction to sudden immersion in cold water: a gasp, rapid breathing and a rise in heart rate and blood pressure. University of Portsmouth researchers report that it fades within a minute or two, once the skin reaches water temperature.

Does ice swimming get easier?

Yes. Finnish research summarised by the Finnish Society of Sport Sciences says habituation happens almost completely within the first two to three sessions. Feeling less cold does not remove the physiological risk, though.

Is ice swimming good for your health?

A 2025 meta-analysis of 11 trials found lower stress 12 hours after cold-water immersion and better self-reported sleep and quality of life, but no change in mood. The authors say the evidence is still limited.

How long should you stay in the ice hole?

We do not give a fixed time. Our guide gives instructions on the spot, and a short dip is the Finnish norm. Follow the guide and your own body.

What is included in the Private Wooden Heated Sauna and Ice Swimming?

A private wooden heated sauna, a handmade ice hole, safety instructions, towels, winter clothing, a light snack and drinks, a guide and pick-up within 10 km of Rovaniemi city centre. It lasts 4 hours and costs from 398 €.

Do I need a swimsuit?

You can bring your own swimsuit if you want; clothes are optional at this private sauna and ice swimming experience.

Ready to book?

You may also like

• Private Traditional Finnish Sauna & Jacuzzi use at Aurora Hill Resort — from 159 €, 1 hour 30 minutes
• Traditional Finnish Sauna Experience — from 149 €, 4 hours

Sources

• Cain T. et al. (2025) Effects of cold-water immersion on health and wellbeing: a systematic review and meta-analysis. PLOS One, University of South Australia
• University of Portsmouth: sport and exercise science research on water safety and cold shock
• Eglin C. & Tipton M. (2005) Repeated cold showers as a method of habituating humans to the initial responses to cold water immersion. European Journal of Applied Physiology
• Smolander J. Avantouinti voi auttaa jaksamaan ja palautumaan. Liikuntatieteellinen Seura (Finnish Society of Sport Sciences)