The Physiological Responses to Cold Water Immersion

 by Sam Kalra

 

Inspired by big personalities on the world stage, increasing numbers of people worldwide are plunging themselves into freezing seas, ice baths and cold showers. Many claim that this practice is life-changing and can even contribute to curing depression and anxiety while others are dubious about the validity of this new craze. So, are there really physiological benefits behind this ‘trend’ or is it all a myth driven by social media?

Studies show that just 20 seconds immersed in water with temperature around 4-5°C can increase concentration and alertness as well as boosting mood. This is thought to be due to two neurochemicals in the body, epinephrine (more commonly referred to as adrenaline in the UK) and dopamine. Epinephrine ( C9H13NO3) and norepinephrine (C8H11NO3) are both neurotransmitters and hormones - as central nervous system neurotransmitters they help to transmit nerve signals across nerve endings to other nerve or muscle cells. However, in relation to cold exposure adrenaline is more important as a hormone. Adrenaline is released from the adrenal gland (from the medulla) and is involved in the body’s flight or fight response. When placed in potentially life threatening situations such as immersion in very cold water, adrenaline is released. Adrenaline helps your body react more quickly - it makes the heart beat faster, increases blood flow to the brain and muscles, and stimulates the body to make sugar to use for fuel. The combination of these factors makes us feel more alert and boosts concentration. It is adrenaline’s ongoing effect after the cold exposure that increases our energy and focus.

 Cold water also causes the prolonged release of dopamine, which helps to elevate mood and happiness long after exposure. Dopamine is a neurotransmitter that makes us anticipate rewards and gives us the desire to complete the action in order to obtain that reward. It has been suggested that the more times the body plunges into cold water, more dopamine will be released and the longer this release will last - therefore increasing mood in the long term. However, unlike dopamine overstimulation through social media and self indulgence that are easily obtainable and can lead to dopamine addictions, the dopamine release generated through cold water immersion is associated with positive challenge without negative impact.

Alongside the biochemical response to cold water, there are neurological responses that can have positive impacts. By forcing the body to do something that it doesn't want to do, in this case immersing itself in freezing water, the prefrontal cortex in the brain is exerting a top-down control over other areas of the brain that regulate reflexes. The prefrontal cortex sits right at the front of the brain and it is involved in executive functions such as self-control, decision making, planning and problem solving. This top-down control builds up resilience and ‘trains’ the mind so when confronted with other situations, the body has more determination to push through the challenge. This grit and perseverance could be applied to most aspects of life - from sport to overcoming challenges at work.

Perhaps a lesser known response to cold water immersion is an increase in metabolism. In the short term, metabolism is increased as calories are burnt in order for the body to warm itself up after exposure. Aside from this, white fat (which stores energy) is converted to brown (highly metabolically active) fat which triggers a more sustained increase in metabolism. Dr Susanna Søeberg, who has a PhD in metabolism at the University of Copenhagen, founded the Søeberg Principle which states that you must force your body to reheat on its own to enhance the metabolic effects of cold water immersion. After exposure, the body will start to shiver. Shivering increases metabolism as it triggers a hormone in the muscles called succinate that stimulates brown fat thermogenesis, which in turn burns calories. Despite not being that widely researched, there are claims that succinic acid (or succinate when in living organisms) has multiple benefits. Succinic acid has the formula C4H6O4 and is used in foods, perfumes and lacquers however, it is also being used as a medicine in the belief that it may bolster the immune and nervous system and also boost concentration, awareness and reflexes. However, as stated above, the credibility of the science behind these claims is not robust. 

Building off these data, ice water exposure has been evaluated and implemented into professional sport as a method of recovery for athletes. After intense exercise involving muscular stress and high cardiovascular demand, an immune response is triggered and immune cells are sent to the specific area in order to repair damaged tissue. Despite repairing the tissue, this response can also lead to pain and swelling of the muscle. Athletes use ice baths as the cold helps to constrict blood vessels, which results in less swelling and therefore less pain. Furthermore, when the body warms itself up after exposure fresh blood is returned all round the body, which helps to flush out any toxins and waste products from tissue breakdown. However, cold water immersion is not beneficial for all forms of training. Cold water has been shown to limit the gains of hypertrophy (the increase and growth of muscle cells) if performed within 4 hours after training - there does not appear to be a negative effect on muscle growth after that period.

There is no doubt that the current level of interest in cold water immersion has been amplified by social media and well known, respected individuals championing its cause but there is scientific evidence behind its practice. As described above, cold water exposure does trigger positive biochemical, neurological, metabolic and muscular responses. Ongoing studies such as that of Dr Heather Masey from the University of Portsmouth lead me to believe that (while more research is needed) the popularity of cold water immersion will grow in the future and even be used as a treatment for some diseases.