Löyly is not decoration: new Finnish research on sauna steam

In Finland, throwing water on the stones has a name. Löyly.

It has always been treated as the soul of the sauna. New research suggests it is also doing real physiological work.

The study

Researchers at the University of Jyväskylä and the Finnish Institute of High Performance Sport published the work in the journal Temperature in July 2026.

Fifty healthy adults completed four 10-minute sauna sessions, each followed by 30 minutes of recovery. They were free to throw as much or as little water as they liked.

The team measured core temperature, skin temperature and heart rate, alongside detailed readings of air temperature and humidity at multiple points in each room.

What they found

Air temperature and relative humidity each raised heart rate and core temperature independently of one another.

Core temperature rose by about 0.4 °C on average across a session, from 37.4 to 37.8 °C.

In plain terms: two saunas set to the same temperature can ask very different things of your body, depending on how much steam is in the air.

Why it matters

Most sauna research has focused on the number on the thermometer. This study says the air's moisture belongs in the conversation too.

It also matches what regular bathers already feel: a round of löyly changes the room fast.

It is also a reminder that sauna is a real load on the heart. Heart rate goes up, the way it does with moderate exercise. That is part of the point, and part of why the safety basics matter.

How we think about it at Norge

The Stillhet Kube carries a Harvia stone heater alongside its infrared elements for this reason. Stones and water give you control over humidity. Infrared gives you gentler, longer sessions.

Some practical notes:

• Start with a few small ladles and let the room settle before adding more.
• Steam intensifies heat quickly, so shorten the session when you add more.
• Drink water before and after. Skip alcohol entirely.

A note on the study

The research was run in collaboration with Harvia, which makes the heater in our Kube, and was partly funded by Toyota. It was a short-term study of healthy, active adults. It tells us how the body responds in the moment, not what happens over years.

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. Laatikainen-Raussi et al., Temperature and humidity independently influence thermoregulatory responses during Finnish sauna bathing, Temperature, 2026
2. University of Jyväskylä release via EurekAlert

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.