Cold water immersion, also known as cold water therapy or cryotherapy, is a practice that involves immersing the body in cold water for therapeutic purposes. It has been studied extensively to understand its impact on the human body, both physiologically and therapeutically. There's been a major spike in popularity in recent years of 'Cold Plunges' and 'Ice Baths' so we thought we would break down the current evidence that surrounds these techniques
Physiological Effects:
When our extremities are immersed in cold water, blood vessels alternate between vasoconstriction and vasodilation. The initial response is vasoconstriction, which reduces the heat loss but then reduces the extremities' temperature. After approximately 5–10 minutes of cold exposure, the sympathetic response causes blood vessels to vasodilate, a process called cold-induced vasodilation. A new phase of vasoconstriction follows the vasodilation, after which the process cyclically repeats itself. With Cold Water Immersion, the body experiences two mechanistically different autonomic responses, namely the cold shock response and the diving response.
The diving response is activated by the wetting and cooling of the face- and nostrils while breath holding. This causes profound sinus bradycardia, peripheral vasoconstriction, inhibition of respiratory neurons, redirection of blood to vital organs, and release of red blood cells stored in the spleen // Hence why it is recommended to put your head under during a cold plunge if possible
The cold shock response is a series of reflexes triggered by signals from cutaneous cold thermoreceptors and causes sympathetically mediated tachycardia, respiratory gasping, uncontrollable hyperventilation, peripheral vasoconstriction, and hypertension
Another effect is an increased metabolic rate. Cold water immersion stimulates the body to work harder to maintain its core temperature, leading to an increase in metabolic rate. This heightened metabolic activity can have implications for weight management and energy expenditure. This is a hotly debated area of cold water immersion. There is evidence that Cold Water Exposure seems to reduce and/or transform body adipose tissue, as well as reduce insulin resistance and improve insulin sensitivity. This may have a protective effect against cardiovascular, obesity, and other metabolic diseases. Where the issue lies is the fact that there are not enough comprehensive conclusive studies to show the level of significance but this may be an area for future research
Therapeutic Effects:
Respiratory and Cardiovascular response:
A group of cold-adapted winter swimmers were investigated and compared to a control group to determine the effect of cold adaptation on cardiovascular risk factors, thyroid hormones, and the capacity of humans to reset the damaging effects of oxidative stress
This study demonstrated that cold-adapted individuals showed an improvement in cardiovascular risk factor markers not seen in the non-adapted group. These findings imply a positive cardio-protective effect of regular Cold Water Immersion
Have you heard about Brown adipose tissue?
A big reason that cold immersion has become popular is the process of ‘browning’ which is where our body increases its use of its own Brown Adipose Tissue in response to a cold stressor as blood flow increases to these issues to create heat. Brown Adipose tissue can burn fat and store energy.
People believe this is reason enough to undergo cold water immersion for the pure reasons of fat loss. Because brown fat deposits in adult humans are only a few grams, Muzik et al (2012) showed that brown adipose tissue thermogenesis only accounts for metabolic energy consumption of <20kcal/day, equivalent to only 2 minutes of moderate-intensity running.
Hormone examples
Repeated cold-water immersions during the winter months of both inexperienced and experienced subjects significantly increased insulin sensitivity and decreased insulin concentrations. Such could be interpreted as a positive health effect although, it is difficult to predict the clinical implications of this finding.
The findings of this study were somewhat limited by the gender differences as well as leaner body compositions of those in the study (Gibas-Dorna, et al - 2016) however, potentially promising as a health benefit with future research
Mental Health
During cold water immersion, the body increases more plasma noradrenaline (attention, arousal and stress reactions) and beta-endorphin (blocks sensaton of pain during a stressor like exercise of cold water) A cold shower or cold water immersion is expected to send an overwhelming amount of electrical impulses from peripheral nerve endings to the brain, which could result in an anti-depressive effect (Shevchuk, 2008) In this study, it was hypothesised that the strong afferent input to the brain from the stimulation of cold receptors in the skin during cold-water immersion could result in an anti-depressive effect. The practical testing of the hypothesis indicated that regular cold-water exposure could relieve depressive symptoms rather efficiently. However, the testing did not include a significant number of participants to make a firm conclusion
Exercise / Recovery / Fatigue
A study by Leeder et al (2019) compared competing professional athletes recovering with and without post-exercise cold water immersion, and assessed recovery using markers of sprint performance, muscle function, and muscle soreness. The cold water group was associated with an improved recovery time of sprint speed 24 hours post-exercise.
The research around cold water immersion / cold water therapy isn't conclusive enough concerning its effect on recovery and improved fatigue. Now although the evidence isn't concrete around this topic and its recommendations, people anecdotally swear by it as a recovery tool. Don't let us talk you out of something that you may feel to be beneficial
Risks
It is important to recognize that cold water immersion can have varying effects on individuals depending on their health status and the specific context of use. Understanding both the benefits and risks associated with this practice is essential for making informed decisions regarding its utilization as a therapeutic intervention.
References
Esperland D, de Weerd L, Mercer JB. Health effects of voluntary exposure to cold water - a continuing subject of debate. Int J Circumpolar Health. 2022 Dec;81(1):2111789. doi: 10.1080/22423982.2022.2111789. PMID: 36137565; PMCID: PMC9518606.
Muzik O, Mangner TJ, Granneman JG. Assessment of oxidative metabolism in brown fat using PET imaging. Front Endocrinol (Lausanne). 2012;3:15.
Gibas-Dorna M, Chęcińska Z, Korek E, Kupsz J, Sowińska A, Krauss H. Cold Water Swimming Beneficially Modulates Insulin Sensitivity in Middle-Aged Individuals. J Aging Phys Act. 2016 Oct;24(4):547-554. doi: 10.1123/japa.2015-0222. Epub 2016 Aug 24. PMID: 26966319.
Shevchuk NA. Adapted cold shower as a potential treatment for depression. Med Hypotheses. 2008;70(5):995-1001. doi: 10.1016/j.mehy.2007.04.052. Epub 2007 Nov 13. PMID: 17993252. Leeder JDC, Godfrey M, Gibbon D, Gaze D, Davison GW, Van Someren KA, Howatson G. Cold water immersion improves recovery of sprint speed following a simulated tournament. Eur J Sport Sci. 2019 Oct;19(9):1166-1174. doi: 10.1080/17461391.2019.1585478. Epub 2019 Apr 6. PMID: 30957673.
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