Cold water therapy

Contrast bath therapy, also known as "hot/cold immersion therapy", or cold water therapy is a form of treatment where a limb or the entire body is immersed in warm water followed by the immersion of the limb or body in cold water.

This procedure is repeated several times, alternating hot and cold.   The same effect can be achieved via a shower with a wide spray head.  You immerse yourself in the shower with a stream of very warm water, then gradually turn the water colder and colder until it is icy.  Then back again to warm and so on.

It is worth noting that exactly the same principles and methods are being used as those used in saunas – where a hot dry sauna is alternated with a cold plunge pool or cool shower.  Thus one should expect the benefits to be the same.

Claims of healing effects

Improving blood circulation

The theory is that warm water causes vasodilation of the blood flow in the limb or body followed by the cold water which causes vasoconstriction, increasing local blood circulation.  The overall effect is intended to be like a pump, hence the alternation between hot and cold.  This has not actually been proven, on the other hand it hasn’t been disproved either.  It means that people with atherosclerosis or hypertension may need to be very careful with this technique, as the sudden violent increases and decreases may trigger a stroke.

Lymph system stimulation

Again the theory is that because the lymph system, unlike the circulatory system, lacks a central pump, alternating hot and cold should dilate and then contract lymph vessels to essentially "pump" and move stagnant fluid out of the area. The theory is that this positively affects the lymph system, which is one of the body's primary mechanism for combatting pathogenic attack and healing damaged tissue.  Again,  this has not actually been proven either, on the other hand it hasn’t been disproved.

Boosting Immune system

The contrast between hot and cold, the cold being something of a shock to the body, is said to boost the immune system.  This may seem odd but there is anecdotal and scientific proof for this:

The immune system appears to be triggered into action by any threat to the system, and cold water is a threat.  But it is worth pointing out that other threats seem to work equally well, for example

On the whole, cold water as a threat is probably more benign than being terrified by the thought of going to hell,  but each to his own.  The scientific proof is found in papers such as this one:

On the whole cold water therapy appears to principally work by this approach – cold water is a threat and the body responds to the threat by boosting the immune system.

Reducing inflammation

In theory, if one wishes to reduce inflammation, one should end the treatment with cold water, as heat will induce the body's inflammatory response, while cold helps to decrease inflammation.  However, the therapy works by stimulating the immune system, and if the person is left cold afterwards and shivering, then the immune system may end up being depressed and any good done will be negated. 

Furthermore, inflammation - however unpleasant and painful - is an indicator that the immune system is working, as the blood vessels dilate and the immune system sends its ‘troops’ to the site of infection.  Thus reducing inflammation does not help the healing process long term, it delays healing and may even halt it. 

So, if anyone suggests contrast bathing or cold water therapy for sports injuries; for any injury presenting with palpable swelling, heat, and visible redness - such as a strain/sprain; or to aid recovery from exercise, they may not be doing you a good turn.  A warm bath to help the healing process may be better.

Methods and Timing

The objective of using the cold water is to fool the body into thinking it is under threat and thus get it to boost the immune system.  But how long hot and how long cold?  The answer is that the hot should be used by far the longest and the cold only used to deliver the requisite threat which boosts the immune system. 

We all know that longer term cold exposure increases an organism’s susceptibility to infection.  Upper respiratory tract infections appear in the cold in winter, not in summer.  The treatment used in tuberculosis pre-war was to bundle the person up so they were as warm as toast, but get them to breathe cold air, thus stimulating the immune response in the lungs.  By being safe and warm and cared for, these patients were under no psychological stress either – psychological stress depresses the immune system.

So you are really trying to induce a pseudo-threat, cold water as a threat that isn’t really a threat at all because you are in control of it, so you will be under no stress.

Furthermore, we know that warmth helps the immune system anyway.   Warmth encourages leukocytes (granulocytes, lymphocytes, and lymphocyte subsets) to be produced and enhances NK cell function.  All the cold does – the threat – is to speed up and add to the effects, whilst releasing these into the blood stream.

It might also be added that exercise also boosts the immune system:

References

• Clin Physiol. 2000 Mar;20(2):114-21.  Adaptation related to cytokines in man: effects of regular swimming in ice-cold water.  Dugué B1, Leppänen E.  PMID:  10735978
• Immune changes in humans during cold exposure: effects of prior heating and exercise  I. K. M. Brenner, J. W. Castellani, C. Gabaree, A. J. Young, J. Zamecnik, R. J. Shephard, P. N. Shek  Journal of Applied Physiology Published 1 August 1999 Vol. 87 no. 2, 699-710 DOI:
• Stress causes reduced natural killer cell activity in mice. - Aarstad H., Gaudernack G., Seljelid R. J.(1983) Scand. J. Immunol. 18:461–464.

Observations

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• Repeated cold water stimulations (hydrotherapy according to Kneipp) in patients with COPD
• The Healing effects of Cold Water Therapy
• Wesley’s Britain in the 1700s - Medical treatments