Cold Water Hardening

Hardening is a procedure in which people expose themselves to cold water either by immersion or by swimming in a winter environment.

Several studies have suggested that cold water swimming has a wide variety of health benefits, including positive changes in hematological and endocrine function, fewer upper respiratory tract infections, amelioration of mood disorders, and improved general well-being.

E.g., Huttunen et al. demonstrated that tension, fatigue, memory, and negative mood in the swimmers significantly decreased with the duration of the swimming period. Also, all swimmers who suffered from rheumatism, fibromyalgia, or asthma, reported that winter swimming had relieved pains.(*)

COLD as a means of therapy

Exposure to cold, when applied reasonably and with moderation, provides a wide range of health benefits.

Cold air or water exposure triggers a set of physiologic reactions, which mostly affect the cardiovascular, hormonal, and immune systems. Cold causes stimulation of the sympathetic nervous system and enhances vasoactivity and mobilization of the immune cells.

Activation of the hypothalamic-pituitary-adrenal axis impacts other regulatory systems, which can explain the positive effect of hardening on immune and hormonal disbalances.

Exposure to cold causes elevated levels of dopamine, norepinephrine, and endorphin, and improves psychical disorders (e.g., stress, depression, and anxiety).

Physical activity in a cold environment requires elevated mobilization of the fat tissue and decreases blood glucose and insulin resistance. This is why hardening treats obesity and helps to eliminate diabetes 2 and other concomitant metabolic disorders.

Cold also alleviates pain, edema, and acute inflammation and promotes restoration of the muscles after strenuous exercise.

Cold Water Immersions and Winter Swimming

Cold‐water immersion is usually practiced in water at temperatures of < 15°C for several minutes. Cold water swimming describes swimming outdoors mainly during the winter when water temperatures range around 5-10°C.

There is rising evidence that winter swimmers are more resistant to certain illnesses and infections. Some papers describe a 40% lower incidence of infectious diseases of the upper respiratory tract in winter swimmers compared to a control group.^(*)

Undesired effects

Cold water exposure promotes health benefits when practiced gradually, deliberately, and with moderation, however, it can also cause undesired effects.

Unaccustomed individuals with underlying cardiovascular diseases may develop life-threatening arrhythmias when exposed to cold water abruptly thus, graded and adaptative mode is required. Also, prolonged cold water exposure can cause hypothermia, which at a certain point is prone to trigger life-threatening arrhythmias.

Author of the review: Kristina Höschlová