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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Cold Immersion and Heart-Rate Variability
Recovery · 2022Regular cold exposure is associated with a modest rise in resting HRV.
HRV trended upward over eight weeks in regular immersers, but the cohort was self-selected and unblinded. We track HRV per client precisely because the group-level signal is weak and individual response varies.
Observational cohort 61 participants Effect strength: Weak
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Delayed-Onset Muscle Soreness After Cold
Recovery · 2018Cold-water immersion reduces perceived muscle soreness after exercise.
Pooled trials show a reliable reduction in perceived soreness 24 to 72 hours post-exercise. Effects on actual performance recovery are smaller and noisier, and chronic use may blunt training adaptation.
Meta-analysis 27 trials Effect strength: Moderate