Science Weekly Sauna and cold plunge: where does the evidence stand?
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Apr 2, 2026 Dr Heather Massey, associate professor studying human responses to cold, discusses saunas, cold plunges and contrast therapy. The conversation covers how heat and cold affect the body, the physiology of cold shock and habituation, observational links to heart health and longevity, and safety and frequency considerations. Short, practical science talk without overclaiming.
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Cold Shock Explains The Post-Plunge Buzz
- Cold water immersion triggers a cold shock response below ~15°C causing a gasp, rapid breathing, and spikes in heart rate, blood pressure, and stress hormones.
- The noradrenaline surge explains the intense buzzing or adrenaline feeling after a cold plunge.
Evidence Is Mostly Small Studies And Observational Signals
- Robust evidence from large randomized trials for health benefits of saunas or cold immersion is lacking; most data are small or observational and heterogeneous.
- Correlative studies suggest signals but cannot prove causation due to confounding and study design limits.
Frequent Sauna Use Correlates With Better Heart Outcomes
- Finnish observational studies link frequent sauna use to lower risks of cardiovascular disease and hypertension, especially in men, but results may reflect lifestyle confounders.
- A proposed mechanism is improved vascular elasticity from repeated vasodilation acting like mild cardiovascular exercise.