Cold water therapy has become increasingly popular over recent years, at least in part due to interest in the Wim Hoff method. The Wim Hoff method simply combines cold water exposure with breathing-based relaxation techniques and cognitive strategies. A lot of claims are made about the benefits of cold water immersion (CWI) therapy, but what is involved, and how many of the claims are backed by evidence?
My name is Bill Frost and I am a PADI certified open water diver with dive experience worldwide. I am also a keen snorkeller and underwater videographer. Increasing my ability to stay in cold Atlantic waters without blur-inducing shivering was why I first explored cold water therapy. I have also raised money for Cancer Research by taking part in various cold water challenges. My open-water swimming training was provided by Sue Lord Open Water Coaching at Westthorpe Lake near Marlow.
Professionally, I am a trauma-focused therapist specialising in EMDR and Cognitive Behavioural Hypnotherapy. I am also a PTSD survivor myself having spent time as an aid worker in the Balkans during the war there. When working with my clients it soon became evident that many ice bath dippers and cold water swimmers do so as part of their trauma resolution journeys. It is important to me that any of my clients embarking on their own cold water journey do so as safely as possible. That is the purpose of this article.
What is cold water therapy?
Cold water therapy is simply deliberate immersion in cold water, with ‘cold water’ generally being defined as water under 15°c. Ice water exposure is at the extreme end of the cold water therapy and is defined as below or equal to 5 °c. Exposure is via cold showers, ice baths and open-water swimming. Durations vary with air temperature, wind speed and levels of body fat, but generally start from 1 minute per degree centigrade for someone already desensitised. A 2018 study concluded that a 10-minute ice bath was as beneficial as a 20-minute ice bath, so returns may diminish with longer exposure times. (Goto et al 2018)
On immersion, breathing is controlled, with the swimmer / ice bath dipper exhaling as they enter the water. Breathwork is continued until the waves of cold shock subside. At ice water temperatures painful burning sensations are experienced and the breathwork also helps to keep responses to these feelings under control.
What are the benefits of cold water therapy?
The benefits of cold water therapy are often cited as including:
- Faster recovery after exercise by reducing swelling and inflammation
- Reduced risk of cardiovascular disease by reducing blood pressure and cholesterol levels
- Immune system boosting resulting in fewer infections
- Improved well-being generally
- Reduced anxiety and depression
- As part of pain management
- Stress tolerance and resilience
- Reduced risk of developing dementia
Cold water therapy and PTSD / trauma / anxiety treatment
Many trauma survivors see a reduction in their symptoms as a result of cold water therapy. However, it should be noted that if the gradual exposure process is too rapid, too infrequent, or taken too far in terms of duration or temperature, then symptoms may worsen. (Anon 2024)
One possible rationale for the efficacy of cold water therapy in the treatment of PTSD is that it may rebalance limbic activity. Cold water shock releases norepinephrine, a neurotransmitter and hormone related to mood, and limbic activity is thought to be modulated by norepinephrine (Harley 1987). Low norepinephrine levels are associated with depression while high levels are associated with PTSD and anxiety.
Equally, if combined with exercise there will be a release of feel-good endorphins which will also help in the treatment of PTSD and depression. Based on conversations with my clients, it seems feasible that cold water exposure may also help to moderate or numb somatised emotional responses. At least one small group research has been undertaken to determine if cold water immersion without exercise generates mood improvements. They concluded that there were positive mood regulation benefits but since the CWI was undertaken in a social group, the improvements may have been due to increased socialisation. (Kelly 2022)
There is a large body of anecdotal case studies and small-scale research projects that more broadly support the efficacy of CWI as part of trauma, PTSD and anxiety treatment. Further research using larger groups of subjects is certainly required to determine the role of CWI in isolation.
Evidence supporting cold water therapy?
Researchers at the Extreme Environments Laboratory at the University of Portsmouth undertake work in this area and have published a meta-study titled “Cold water immersion: kill or cure?” Their 2017 review concluded that in most instances there seemed to be a credible rationale for the benefits proposed, but that further research was required. (Tipton et al 2017). A narrative review published in 2020 came to similar conclusions. (Knechtle et al 2020).
However, much of the available evidence is based on studies that looked at small groups eg triathletes or open-water swimmers where benefits may be due to the impact of exercise and lifestyle. Other papers are anecdotal and describe individual experiences. Some studies suggest that the Wim Hof method may help with inflammatory-related conditions. But further research is needed to tell if the benefits are due to cold water exposure or the associated relaxation techniques.
What are the risks of cold water therapy?
Cold water immersion generates a controlled, but substantial, physical stress response. Many of the benefits such as improved immune responses are thought to be due to the biological effects of this intense burst of stress. However, there are some risks associated with mismanaged cold or ice water immersion. These include:
- Danger of drowning if diving into cold water due to cold water shock which can result in spontaneous inhalation
- Heart arrhythmias (heart rhythm disorders) mainly in athletes who exercise immediately after cold water immersion
- Heart attacks due to pre-existing heart conditions and the cardiac impact of cold water shock
- Hypothermia resulting from being immersed for too long
- Danger of tissue damage (frostbite) with ice water temperatures and a lack of hand / foot protection
All of these risks can be moderated or removed entirely. If you have hyper or hypotension, cardiac issues generally, asthma and any other health issue that might impact your safety then discuss your options with your GP. In all cases, you should build your tolerance for cold water immersion gradually over time. This can be achieved by starting with brief cold showers, then summer lakes perhaps and building up tolerance before getting down to ice water temperatures. Ice bath owners have slightly more control over the temperature but will still need to acclimatise gradually over time before adding ice to their ice bath.
How do I safely go cold water swimming?
Cold water swimming involves swimming in lakes, rivers or the sea at times of the year when water temperature is below 15°c. Not all locations are suitable and you are strongly advised to join a local wild swimming group and receive safety training before swimming.
If your acclimatisation has been in ice baths, a lake will feel colder. This is due to the absence of body-heated water around you due to the movement of swimming. If you move around in your ice bath there is little difference. Some people wear wetsuits when swimming to allow them to stay in the water for longer. You may need help getting out of a wetsuit given that your hands will be numb.
Before going into the water
- Discuss with your GP if you have hyper or hypotension, cardiac issues generally, asthma and any other health issue that might impact your safety.
- Make sure you have everything you need for the swim eg tow float, hi-visibility hat, goggles, a whistle and for the time afterwards ie a towel, warm clothes and ideally a warm changing robe.
- Carefully evaluate weather conditions before you swim: look at weather forecasts and also look at the reality in front of you. If the weather changes as you are swimming get out.
- Do not swim if there is a risk of lightning or fog or very strong winds.
- Understand the water and air temperature just before you swim and adjust your swim time accordingly. If it is a windy day this will increase the wind chill factor so reduce your swim time. When the water temperature is colder than the air temperature the water will feel colder, when the water temperature is higher than the air temperature the water will feel warmer.
- Eat something before swimming, but not a large meal.
- Alcohol accelerates hypothermia so do not consume alcohol before cold water swimming or when hung over.
- Don’t try to match other people’s in-water durations. Their duration will depend on their individual situation and the level of tolerance they have built up over time.
- Cover small cuts or scratches with waterproof plasters or spray plaster. Don’t swim with open wounds which may become infected or be a pathway for pathogens.
- Wear a watch that you can see without needing glasses and make a mental note of the time you went in.
- If there is any doubt in your mind in terms of whether it is safe for you that day to swim, don’t swim.
- Do not swim alone and ideally swim in locations where there is a lifeguard on duty.
When you are swimming
- Don’t dive in. Enter the water slowly to control your breathing and only put your face in the water when your breathing is in control. This prevents cold shock water inhalation.
- Head-up swimming styles are better, at least initially.
- Stay away from wildlife and other water users.
- The stages of hypothermia are: “mumble, stumble and fumble”. As you get colder it will become increasingly difficult to move your arms and legs. This affects your ability to swim and to get out of wet clothing when you get out. So get out way before you become hypothermic.
Getting out of the water
- Get out of the water slowly and get into dry clothing as soon as possible. Avoid warm showers until you have warmed up. Especially if you are hypotensive, this could result in fainting.
- You may start to shiver sometime after you get out of the water due to the continued cooling of the body. You should not drive until the shivering subsides and you are fully in control of your body. Do not drive until it is safe for you to do so.
- Have something to eat and a hot drink after you get out. Wash your hands before eating since open water may contain pathogens.
Open-water swimming is a safe pursuit but does require careful consideration of the risks involved. In the sea this can include tides, currents, pollution and marine life; in lakes this can include flood water contamination, toxic algae and Weil’s disease; in rivers this can include the presence of sewage and again the risk of Weil’s disease. (Rew 2022)
References (in no particular order)
Knechtle B, Waśkiewicz Z, Sousa CV, Hill L, Nikolaidis PT. Cold Water Swimming-Benefits and Risks: A Narrative Review. Int J Environ Res Public Health. 2020 Dec 2;17(23):8984. doi: 10.3390/ijerph17238984. PMID: 33276648; PMCID: PMC7730683.
Tipton, M.J., Collier, N., Massey, H., Corbett, J. and Harper, M. (2017), Cold water immersion: kill or cure?. Exp Physiol, 102: 1335-1355
Rew, K. (2022). The Outdoor Swimmers’ Handbook. Random House.
Goto Y, Hayasaka S, Kurihara S, Nakamura Y. Physical and Mental Effects of Bathing: A Randomized Intervention Study. Evid Based Complement Alternat Med. 2018 Jun 7;2018:9521086. doi: 10.1155/2018/9521086. PMID: 29977318; PMCID: PMC6011066.
Anon, (n.d.). Ice baths, Wim Hof and PTSD – PTSD UK. [online] Available at: https://www.ptsduk.org/ice-baths-wim-hof-and-ptsd/ [Accessed 6 Feb. 2024].
Harley CW. A role for norepinephrine in arousal, emotion and learning?: limbic modulation by norepinephrine and the Kety hypothesis. Prog Neuropsychopharmacol Biol Psychiatry. 1987;11(4):419-58. doi: 10.1016/0278-5846(87)90015-7. PMID: 3321150.
Kelly JS, Bird E. Improved mood following a single immersion in cold water. Lifestyle Med. 2022; 3:e53.