Some science behind the scenes

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:

Dr. Rush refers to the cases related by Van Swieten and Smollett of consumptive patients recovering their health from falling into cold water, … (Medical Inquiries and Observations. By Benjamin Rush, M D., Professor of the Institutes and Practice of Medicine, and of Clinical Practice, in the University of Pennsylvania. 4 vols, in two. 4th Edit. Philadelphia, 1815, II, p. 83).

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

Tissot cites from Mead the case of a young woman, aged 28, who laboured under all the symptoms of confirmed phthisis [tuberculosis], and was threatened with death, when exaggerated fear about the state of her soul began to torment her. Alarm, increased by the discourse and exhortations of friends, perhaps more pious than enlightened, threw her into a state of religious insanity. The consequence, as respects the bodily condition, was that the hectic fever, the expectoration, the sweats, the emaciation and other unfavourable symptoms disappeared, and led to the hope of cure.  (Annales Medico-Psychologiques. Edited by Baillarger, Cerise, et Longet, Sept., 1867, p. 167).

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:

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:

This study examined the immunological responses to cold exposure together with the effects of pretreatment with either passive heating or exercise (with and without a thermal clamp). ……. Before exposure [to the cold], subjects participated in one of four pretreatment conditions.

  • For the thermoneutral control condition, subjects remained seated for 1 h in a water bath at 35°C.
  • In another pretreatment, subjects were passively heated in a warm (38°C) water bath for 1 h.
  • In two other pretreatments, subjects exercised for 1 h at 55% peak oxygen consumption (once immersed in 18°C water and once in 35°C water).

Subsequent cold exposure induced a leukocytosis and granulocytosis, an increase in natural killer cell count and activity, and a rise in circulating levels of interleukin-6. Pretreatment with exercise in 18°C water augmented the leukocyte, granulocyte, and monocyte response. These results indicate that acute cold exposure has immunostimulating effects.


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:

Immune changes in humans during cold exposure: effects of prior heating and exercise 

Before each treatment, the average leukocyte count was within the expected normal range of 4.5–11.0 × 109 cells/l. Cell counts were not significantly altered when the subjects remained seated in the 35 and 38°C water baths. In contrast, exercise with or without a thermal clamp induced a significant rise in leukocyte, granulocyte, and lymphocyte counts. ……………

At entry into the cold chamber, total leukocyte counts were significantly higher when subjects had previously exercised with a thermal clamp. After …. cold exposure, total white cell counts had increased significantly in all four pretreatment conditions, and values remained elevated after [more] cold exposure. Significantly more leukocytes were recruited into the circulation after … cold exposure, if the pretreatment was exercise with a thermal clamp rather than the control condition.

Granulocyte counts followed a similar pattern of response to the total leukocyte counts, increasing significantly [after] cold-air exposure . Compared with the control condition, a significantly greater number of granulocytes were recruited into the peripheral circulation when subjects had previously exercised with a thermal clamp.

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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