bradley said:

They aren't just beneficial because of the absence of hot water; there are tons of studies that show direct benefit of cold water therapy. Here, have some wikipedia.

A reported study from the Thrombosis Institute in London into the effects of the cold bathing found that volunteers that followed a disciplined daily regime had increased immune white blood cells and the level of the bodies natural blood thinning enzymes substantially increased, improving micro circulation. It also stimulated the production of hormones such as testosterone in men, and boosted women's production of estrogen. Cold water immersion raises thresholds of pain tolerance, and aids adaptation to cold, reduces muscle spasm, can influence the frequency of respiratory infections and improve subjective well-being. It may cause an immunological modulation in terms of the Th1-type pattern, which is a proinflammatory cytokine profile. It is involved in diseases such as arthritis,[56] diabetes,[57][58] inflammatory myopathies, inflammatory bowel disease,[59] psoriasis, CFS, fibromyalgia, chronic pain, fatigue conditions,[60] auto immune disease and other inflammatory conditions. Cold water adaptation reduced total cholesterol and LDL cholesterol, lowered plasma viscosity and blood pressure rate product. Cold water immersion reduces recovery time in athletes,[61] enhances repeat performance and reduces exercise induced muscle damage.[62]

Cold water exposure challenges both the neuro-endocrine and the immune systems, reduces stress hormones and attenuates their response. Increases ADH and cortisol and increases immunomodulatory cytokines.[63] Cold water exposure and adaptation can modify the sensory functions of hypothalamic thermoregulatory centres to lower heat loss and produce less heat during cold exposure and have immunostimulating effects.[64] The thermogenic action of adrenaline in cold exposure produces heat and may reduce this stress hormone.[65]

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