Whole-body cryotherapy

Whole-body cryotherapy (WBC) exposes the body to extreme cold air, typically −100 to −140°C, for 2–4 minutes inside a nitrogen-vapour or electric cryo-chamber, in contrast to cold-water immersion (CWI) at approximately 10–15°C for 10–15 minutes; the two modalities differ substantially in cooling rate, depth of tissue cooling, and physiological response. Proposed mechanisms include acute noradrenaline and endorphin release, transient anti-inflammatory cytokine shifts, and sympathoadrenal activation followed by a parasympathetic rebound. A 2015 Cochrane review (Costello et al., CD010789) found insufficient evidence to determine whether WBC reduces muscle soreness or improves recovery compared with passive rest, rating evidence quality as low to very low; evidence for immune, metabolic, or longevity-specific effects in healthy adults is preliminary. WBC carries risks of frostbite, hypoxia from nitrogen vapour, and cardiovascular stress, and is contraindicated in cold urticaria, Raynaud's phenomenon, and severe cardiovascular disease.