What your heart does in 7 °C water

The question we hear most from buyers over 50 about ice baths is simple. Is it safe for my heart?

A 2026 study from Geneva gives some real data.

The study

Cardiologists from Geneva and Lausanne University Hospitals studied 20 recreational athletes aged 45 and over, with a mean age of 56. Eleven were women. Around a third had a high ten-year cardiovascular risk score.

Each wore a waterproof ECG monitor for ten days around the Geneva Christmas Cup, the world's largest cold water swimming event.

The team recorded 64 cold water immersions at an average of about 7 °C.

What they found

Heart rate rose by about 40 beats per minute during immersion.

Across the ten days, most participants had brief, mostly benign rhythm irregularities, which is common. Only one short event happened during immersion.

The rate of these events was not significantly different between cold water periods and the rest of the monitoring period.

How to read it

Reassuring, within limits. These were twenty active, trained people. It does not tell us about people with heart disease, and it was a small study.

That 40 beat jump is also the cold shock response at work. It is real, and it is why technique matters.

Using an ice bath well

• Start warmer than you think. The N-02 lets you set the temperature, so you can build down gradually.
• Enter slowly. Control your breathing before your shoulders go under.
• Keep early sessions short.
• Never plunge alone when you are starting out.
• If you have a heart condition, speak with your cardiologist first.

Free: The Norge Longevity Guide. Heat, cold and light after 50, with the evidence and the safety rules in one place. Get the guide.

Sources

1. Merkt et al., Cardiac arrhythmia during cold-water immersion: a self-controlled field study, 2026
2. Full text (PMC)

This article is general information, not medical advice. If you have a heart condition, low blood pressure or are pregnant, speak with your GP before using heat or cold.