A 90-second lake dip between sauna rounds kept core temperature and heart rate lower
The 2026 Experimental Physiology study put 16 adults through two rounds at 84.5°C in a lakeside sauna in Wales. On one day their breaks were in air only, and on the other each break began in the lake.
The paper
Thermal and cardiovascular responses to sauna are attenuated by adding cold water immersion to cooling breaks
Owen TF, Giles CJ, Leaney SF, Coombs GB, et al.. Experimental Physiology, 2026:EP093626.
See the study at a glance
- Design
- Crossover trial in which everyone did both days in a balanced order
- People
- 16 adults (8 women)
- Who they were
- Healthy adults aged 31 on average. They were tested at the public Sawna Bach sauna beside the lake in Llanberis, North Wales.
- What they did
- Two 15-minute rounds at 84.5°C and 16.3% humidity. A 10-minute break in 23°C air followed each round, and on the dip day each break began with 90 seconds neck-deep in 19.9°C lake water. A rectal probe tracked core temperature through a 30-minute recovery.
- How long
- One session on each of two days
These numbers came out of it
37.55°C
At the end of the second round, core temperature was 37.55°C on the dip day and 38.03°C on the air-only day.
108 bpm
Heart rate at the end of the second round was 108 beats a minute on the dip day. On the air-only day it reached 125.
0.63°C
Core temperatures on the two days were furthest apart 15 minutes into recovery.
18 bpm
The biggest heart-rate difference between the days came 5 minutes into recovery.
The researchers did this
Sixteen healthy adults visited a public lakeside sauna in North Wales on two days. Each day they did two 15-minute rounds at 84.5°C. A 10-minute break in 23°C air followed each round, and a 30-minute recovery closed the session.Source 1 · Crossover trialThermal and cardiovascular responses to sauna are attenuated by adding cold water immersion to cooling breaksOwen TF, Giles CJ, Leaney SF, et al.. Experimental Physiology, 2026.Read the paper ↗PubMed ↗ On one of the days each break began with 90 seconds up to the neck in 19.9°C lake water. The researchers balanced the order of the two days across the group.
At the end of the second round, core temperature read 37.55°C on the dip day and 38.03°C on the air day. Heart rates were 108 and 125 beats a minute.Source 1 · Crossover trialThermal and cardiovascular responses to sauna are attenuated by adding cold water immersion to cooling breaksOwen TF, Giles CJ, Leaney SF, et al.. Experimental Physiology, 2026.Read the paper ↗PubMed ↗ Measured from the start of the session, heart rate climbed 41 beats with the dips and 57 without.
The two days kept pulling apart after the last round. Heart rates were furthest apart 5 minutes into recovery, when the dip day ran about 18 beats a minute slower. The core temperature difference peaked at 0.63°C after 15 minutes.Source 1 · Crossover trialThermal and cardiovascular responses to sauna are attenuated by adding cold water immersion to cooling breaksOwen TF, Giles CJ, Leaney SF, et al.. Experimental Physiology, 2026.Read the paper ↗PubMed ↗ People lost 0.56 kg of sweat on the dip day and 0.72 kg on the air day, and that difference wasn't statistically significant.
Blood pressure differed less. Systolic pressure (the top number) and mean pressure were the same on both days. Diastolic pressure (the bottom number) ran lower on the air day during the breaks and 20 minutes into recovery.Source 1 · Crossover trialThermal and cardiovascular responses to sauna are attenuated by adding cold water immersion to cooling breaksOwen TF, Giles CJ, Leaney SF, et al.. Experimental Physiology, 2026.Read the paper ↗PubMed ↗ With the dips, people rated the second round nearly one step easier on the researchers' comfort and tolerance scales.
The study can't tell you these things
- It tested one session, so it can't say what regular dips do over months of sauna use.
- Water at 19.9°C is mild compared with a typical cold plunge.
- Blood pressure wasn't measured inside the sauna.
- Bench temperatures in the public sauna ranged from about 70.5°C to 85.5°C.
- The 16 participants were healthy, so the results don't cover people with heart disease.
People quote it like this
The dip result is easy to stretch into proof that ending on cold burns fat or that contrast beats either half alone. The trial measured core temperature, heart rate, blood pressure, sweat and comfort over one session, and none of that speaks to fat or long-term health.
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We cited these sources
- 01Owen TF, Giles CJ, Leaney SF, Coombs GB, Oliver SJ. Thermal and cardiovascular responses to sauna are attenuated by adding cold water immersion to cooling breaks. Experimental Physiology. 2026:EP093626. doi:10.1113/EP093626 PMID 42390474