Dr Heather Massey, University of Portsmouth, UK
I’ve always been fascinated by the impact cold water has on the body. As a child, I wondered why I could stay in water unaffected by the cold, while adults tended to wear wetsuits. The individual variation in response to environmental stressors fascinates me still.
I started swimming outdoors as a child. My father was a keen dinghy sailor, so we would spend many an hour on our local canal learning to sail. Mostly this involved capsizing, then swimming a bit to get back in the boat. This is the main reason my brother and I learnt to swim. My dad tells me I enjoyed being in the water more than being in the boat.
We spent many summer days messing about on boats with my dad or on holiday in North Wales at the seaside.
I had a brief hiatus as a teenager and into my mid-20s playing rugby, football and hockey. But I soon realised that I spent more time rehabilitating in the pool and swimming outdoors than I did on the pitch playing.
I retired from field sports and went back to long-distance outdoor swimming. I really enjoy swimming in new places, with different people, learning about where they swim and seeking out new challenges.
The impact of creature comforts on the human body
Evolutionarily, humans are hunter-gatherers, with frequent periods of exposure to cool environments, feast and famine. Our bodies weren’t evolved for the general comforts of Western society, warm homes, long periods of sitting and readily available food. Putting our bodies under some stress is important to ensure that we can continue to adapt to stressors when they arrive and be able to maintain health for as long as possible.
Some people may go jogging or running for me, cold water swimming provides that challenge. Immersing the body in cold water is a stimulating experience, both physically and mentally. Cold-water stimulates a rapid breathing response and requires some mental preparation in order to get in the water.
Why should we challenge our bodies and put them to the test?
Providing challenges to our bodies results in adaptive responses to the environment and physical challenges faced. In theory, this should make it less stressful when exposed to that environment or exercise again. We see this in athletes, through their regular training their physiology adapts and enables improved athletic performance.
Exposure to a range of different extreme environments triggers a similar response. Those frequently exposed to cold water experience a shorter and less severe response. The same is true for altitude; those adapted to altitude are better able to perform at altitudes.
The risks of cold-water swimming
Cold shock occurs immediately on exposure to cold water because the skin of the body is cooled rapidly. Your body responds with an inspiratory gasp reflex and rapid, uncontrolled breathing, along with increased heart rate and blood pressure. These responses can be problematic for a number of reasons. These problems are well documented and form part of water safety education delivered to children and adults every year.
If you jumped into the water or a wave broke over your mouth whilst your breathing is uncontrolled, you could end up breathing in water, which could lead to drowning. If you have an underlying heart condition the rapid increase in blood pressure and heart rate can result in changes to the rhythm of your heart beats or even a heart attack.
Potential benefits of cold-water immersion
There is a large volume of qualitative and anecdotal evidence for the potential benefits from cold water immersion or swimming (2-4, 8). The research about the benefits lags behind the well-developed science of the negative effects.
Some studies have looked at cold showering. Individuals who shower for 30 seconds in cold water on a daily basis saw a reduction in the number of days of self-reported sickness.
There are a range of studies investigating different conditions and the impact that outdoor swimming may have, including menopause and neural degeneration. However, the research into the potential benefits of immersion in cold water is still in its infancy.
A boost for our well-being?
The evidence of improvements to mental health using cold-water swimming is limited to qualitative and anecdotal evidence and small feasibility studies (1,8). Recent work shows that cold water swimming could improve a person’s wellbeing and has showed signs of reducing symptoms of depression (1,5-8). We now need to support this with more rigorous scientific methods.
My research team and I are working on a feasibility study using a randomised control design to investigate if outdoor swimming has any positive impact on symptoms of depression.
Physical, psychological and society – understanding the potentials
There are different potential mechanisms for the impact that cold water swimming may have on mental health. Some of these explanations are based on physiology. They include a theory about cross-adaptation. In this instance, an individual may be adapted to swimming in cold water and this has a knock-on effect to another stressor in a person’s life.
Other reasons include reductions in inflammation since inflammatory processes can be found in some forms of depression. An increase in stress hormone is another possibility, caused by the cold shock response and leads to increases in dopamine and serotonin levels. These are commonly considered to be part of what’s called the ‘post-swim high’. Cold water swimming may also be related to a reduction in the rate at which nerves fire.
Psychological and social factors may also play a part. These include being with a familiar group of people you feel connected to, wanting to try a new challenge, doing exercise, being distracted, being outdoors. All of which have a cathartic effect.
There are several potential reasons why swimming outdoors may have an impact on a person’s mental health. If outdoor swimming does have an effect, the next steps will be to establish which of these factors are relevant and for whom.
REFERENCES
- Burlingham A, Denton H, Massey H, Vides, N, Harper CM. Exploring the engagement and effectiveness of a sea swimming course as a novel intervention for anxiety and depression: A feasibility study (in review) Physical Activity and Mental Health
- Denton H, Aranda K. The wellbeing benefits of sea swimming. Is it time to revisit the sea cure? Qual Res Sport Exerc Heal. 2019;12(5):647-663
- Foley R. Swimming in Ireland: Immersions in Therapeutic Blue Space.” Health & Place 201535: 218–225.
- Foley R. Swimming as an Accretive Practice in Healthy Blue Space.” Emotion, Space and Society 22: 43–51.
- Massey H, Denton H, Davies C, Harper CM, Gorczynski P. Mood and wellbeing of novice open water swimmers and controls during an introductory outdoor swimming programme. A feasibility study. Lifestyle Medicine.2020 1:e
- Massey H, Gorczynski P, Harper CM, Sansom L, McEwan K, Yankouskaya A, Denton H. (2022) Evidence of Impact of Outdoor Swimming on Health: Web-Based Survey. Interact J Med Res 2022;11(1):e25589 doi: 2196/25589
- Tipton, M, Collier, N, Massey H, Corbett J, Harper M. Cold water immersion kill or cure? Exp Physiol. 2017 102, 1-
- Van Tulleken C, Tipton M, Massey H, Harper M. Open water swimming as a treatment for major depressive disorder BMJ case reports 2018 http://dx.doi.org/10.1136/bcr-2018-225007