The evidence
What the studies actually say —
including where they are thin.
Moderate evidence for reduced inflammation and short-term mood lift; weaker evidence for the bigger claims. We report study type, sample size, and an effect size we don't inflate.
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Habituation of the Cold Shock Response
Safety · 2017Repeated short exposures blunt the initial cold shock response.
After six immersions the gasp reflex and the spike in heart rate and ventilation fell substantially. This is the most robust finding in the field and underpins our short, supervised early sessions.
Controlled laboratory study 18 participants Effect strength: Strong
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Cardiovascular Load During Cold Immersion
Safety · 2019Sudden cold immersion sharply raises cardiac workload.
Immersion produced immediate rises in heart rate, blood pressure, and cardiac output. This is exactly why we screen for cardiac risk first and supervise every session; the load is real and not trivial.
Physiological monitoring study 42 participants Effect strength: Strong