Five minutes in an ice bath more than doubled noradrenaline at either time of day
A 2025 Scientific Reports study gave 12 adults a five-minute ice bath in the morning and another in the evening, on separate days, and tracked their hormones and blood fats.
The paper
Effects of time-of-day on the noradrenaline, adrenaline, cortisol and blood lipidome response to an ice bath
Braunsperger A, Bauer M, Brahim CB, Seep L, et al.. Scientific Reports, 2025;15(1):1263.
See the study at a glance
- Design
- Crossover study in which each person bathed at both times of day
- People
- 12 adults (6 women, 6 men)
- Who they were
- Healthy adults in Germany. Their average age was 26 and their average BMI 23.
- What they did
- A 5-minute warm-up at 50 watts, then 5 minutes in 8–12°C water up to the armpits. Participants kept one arm out for blood draws and used a breathing technique they had practiced. Blood was drawn before the bath and at 5 and 30 minutes afterward.
- How long
- Two sessions on separate days
These numbers came out of it
+127%
Plasma noradrenaline rose from 395 to 896 pg/ml five minutes after the morning bath.
+144%
After the evening bath, plasma noradrenaline climbed from 385 to 937 pg/ml at the same five-minute mark.
No change
The bath didn't significantly change adrenaline or cortisol.
Not measured
The study didn't measure dopamine or the energy the bath burned.
The researchers did this
Twelve healthy adults in Germany took one ice bath in the morning and another in the evening on a separate day. Half were women. Each session started with a 5-minute warm-up at 50 watts before 5 minutes in 8–12°C water up to the armpits.Source 1 · Crossover trialEffects of time-of-day on the noradrenaline, adrenaline, cortisol and blood lipidome response to an ice bathBraunsperger A, Bauer M, Brahim CB, et al.. Scientific Reports, 2025.Read the paper ↗PubMed ↗ Ice kept the water in that range. One arm stayed out for blood sampling, and everyone used a breathing technique they had practiced.
The responses looked alike at both times of day. Five minutes after the bath, plasma noradrenaline was up 127% in the morning and 144% in the evening.Source 1 · Crossover trialEffects of time-of-day on the noradrenaline, adrenaline, cortisol and blood lipidome response to an ice bathBraunsperger A, Bauer M, Brahim CB, et al.. Scientific Reports, 2025.Read the paper ↗PubMed ↗ Neither adrenaline nor cortisol changed significantly with the bath, although cortisol ran higher in the morning at every time point.
Fatty acids in the plasma rose only after the morning bath. They went from 5.1% to 6.0% at five minutes and reached 6.3% at 30 minutes. Women and men responded alike.Source 1 · Crossover trialEffects of time-of-day on the noradrenaline, adrenaline, cortisol and blood lipidome response to an ice bathBraunsperger A, Bauer M, Brahim CB, et al.. Scientific Reports, 2025.Read the paper ↗PubMed ↗ The study didn't measure dopamine or energy use, and the authors list the missing energy data as a limitation.
The study can't tell you these things
- Only 12 people took part.
- Everyone warmed up before the bath, and the authors acknowledge the warm-up could have shaped the hormone results.
- It didn't measure dopamine, so it can't speak to dopamine claims about ice baths.
- Each person took one bath at each time of day, so the study says nothing about regular plunging.
From our sister magazine
Sauna Monthly compares ice barrels and chiller tubs
We cited these sources
- 01Braunsperger A, Bauer M, Brahim CB, Seep L, Tischer D, Peitzsch M, et al.. Effects of time-of-day on the noradrenaline, adrenaline, cortisol and blood lipidome response to an ice bath. Scientific Reports. 2025;15(1):1263. doi:10.1038/s41598-025-85304-8 PMID 39779795