Tag Archives: Cold Acclimatization

Cold Water Acclimatization

This post was a companion to HABITUATION, both of which I wrote in early 2010. Since I revisited and largely rewrote that as Cold Water Habituation, my plan was to do the same in this post also.

Acclimatization (acclimatisation for those of us who forego the use of the z)  is a different factor to habituation.

While habituation is simply the process of adapting to getting into cold water, acclimatization is about a person’s ability to stay in cold water for longer.

(Acclimation is the same process but done in controlled or lab conditions).

In brief, as every open water swimmer knows, the more you train in cold water, the better you will be able to tolerate the cold, and the longer you will be able to swim in the water.

Acclimatization is a more difficult and often almost mysterious process than habituation. It takes longer to develop and longer to lose. It tests one far more, requiring a greater willingness to push ourselves.

I’ve luckily gotten to know a lot of cold water swimmers, originally through the Sandycove swimmers group, many of whom say you can think your way through cold, at least up, to a certain point. I know one swimmer and psychologist who helps people in this area, and stress overcoming the fear, that the swimmer should tell themselves that they are warm when they feel the cold, or to focus on different subjects, or to imagine they swimming in warm water, etc. These are classic sports visualization methods that are used to transcend different problems.

Guillamenes platform during winter storm, long exposure
The Guillamenes platform during a winter storm, (long exposure)

I have certainly found for myself that even getting into  6 or 7 º C., after the first minutes of pain, that I now have a definite whole-body feeling of warmth, (excepting feet and hands).

However, there is the problem that physics and the laws of thermodynamics are absolute. A favourite quotation of mine is  “eventually the dead hand of the Second Law will hold sway over everything”. (Yes, I have a melancholy bent). However, this alludes to the fact that entropy increases and heat is lost in everything in the universe. As open water swimmers we are affected by such facts as:

  • One loses heat in water at 30 times the rate in air (thermal conductivity).
  • Heat loss is slower on sunny calm days than overcast windy days which strip body heat away even more quickly.
  • You lose 10% of your heat through your head, (in proportion with the rest of your body).
  • The ratio of heat loss is proportional to the volume and surface area, so larger people lose heat more slowly as the ratio of volume to surface area is increased.
  • Fat is an insulator and slows heat loss.
  • Insufficient food and fluids, alcohol intake, illness or not enough sleep all make one feel colder.
  • Pockets of changing water temperatures have a significant effect.
  • The Second Law of Thermodynamics: In a closed system, entropy increases. In the case of swimming, the closed system is the body, the air and the water. heat will flow from the warm body to the cooler water. You lose heat unless you input sufficient heat energy.
  • No-one is immune to heat loss or hypothermia.

Put all that together and all you get is what you already know. You get colder quicker in water, but the rate of change is dependent on a range of factors.

One factor I didn’t put in there is the mental aspect, because it’s difficult to see how thought (Werner Heisenberg & Quantum Mechanics aside :-) ) can have any effect on the rate of change of the system, i.e. how can thought slow your cooling rate? Many experienced swimmers will say you can think your way into extending your time in the water. I’d never been able to say this. I do believe that you can stay calmer, and accept what’s happening, which makes it feel easier.

I think that you get more used to being in cold, and you recognise your early hypothermia indicators better so you can push your limits more. You learn to swim further into your own cold experience. You get better at preparing and recovering. Some of those very experienced swimmers I know have learned to accept and box off the cold, realise it’s there, know the efficiency is decreasing but at the same time know there can be a long gap between the early hypothermia indicators and remaining period during which much swimming can still be done.

The simple positive feedback process of improving cold ability
The simple positive feedback process of improving cold ability

There is also the case that with improving  habituation, that heart rate and stress hormones decrease, and therefore the person feels better about getting into cold water and less nervous. Less heat will be lost in the initial minutes, which also leads to greater capability. This is the positive adaptive feedback system that I wrote about a couple of weeks ago.

The small improvements drive confidence, the confidence allows the swimmer to push themselves while staying more relaxed. The mental aspect of cold water swimming was the single thing I most struggled to understand in my first few years of winter swimming. It seemed too trite, too easy, without really saying anything useful. It is easy to say that mental attitude allows one to swim longer but it has taken me years of winter cold water swimming to really realise this, to integrate it and to try to convey it. To understand what it means and to comprehend the effect that thought has on my own cold acclimatisation and ability, and not least to be able to explain that better for myself and hopefully others.

It has not been a short journey. If I could do it, so can you.

Cold Water Habituation

HABITUATION was one of my very first posts, and the first post I wrote about cold and cold water swimming, over four years ago, little realising it would become my favourite subject. Although it is linked in the Cold Water Articles Index, I decided to air it out and rewrite it. (And change those capitals).

Back then I mentioned how I  had progressed in cold. I used myself as an example to demonstrate progressive cold water ability. I was previously a surfer, wearing wetsuits year round and thinking I knew what real cold was. I later realised I had only ever once been close to getting as cold as I regularly get as an open water swimmer after 30 or 40 minutes. I had been surfing for six hours straight with no hood in winter that time.

 I started swimming open water during summer, but wore a wet-suit for the first winter for very irregular swims, and I was still surfing regularly. Toward the end of my second winter of swimming, which wasn’t as regular as I swim now, I decided to do my first non-wet-suit swim of the year, which was in late March I think, only a month after what is usually the lowest temperature of the winter here. March is still very cold water. 

Ballydowane Cove across to St. John's island
Ballydowane Cove across to St. John’s island

I clearly recall, will never forget in fact, arriving at Ballydowane Cove on a cold Sunday morning, with chest high waves, and feel physical effects of profound apprehension, even fear.

I recall that first experience of 7 or 8 degree water like it was yesterday, and I swam for 10 minutes. Disappearing in the waves, and ending up swimming the short length of the beach, and taking ten minutes to so do, and having warned her I’d only be in for a few minutes, Dee thought I’d been drowned. It seems a long time ago. The fear lasted for the next few swims before it disappeared.

The process of getting inured to getting into cold water is called Habituation.

It is not special, it’s not a reflection of an innate ability to handle cold. it doesn’t mean or signify anything. It’s a purely physical response and almost everyone can do it. (Excluding people with cardiac problems or certain circulatory or cardio-respiratory illness or other underlying contra-indicated health issues).

It will hurt for a few seconds or even a few minutes. Increased adrenaline beforehand may elevate your heart rate before you get in the water. You will find it difficult to breathe the first minute or so. You may flail about for the first one hundred metres. You can just relax and float in the water, you don’t have to swim. In fact that’s what King of the Channel Kevin Murphy prefers to do in cold water.

But, you will also settle and relax and get used to it.

coldI know it won’t kill me.

This is a primary mistake that some people make. They think that other swimmers, (more capable or tougher swimmers than them, in their mind), don’t feel it. They do. I do. It just matters less. Of course I also feel the same about other’s swimmers capability. Somewhere is a swimmer who really is better at cold than everyone. It make be Finbarr Hedderman. Or Kevin. Or Fergal, or Lisa or Alison or someone else. But we are all on the same spectrum of tolerance, just in different locations.

When I wrote this in 2010, I’d just met cold water Sandycove legend and Channel swimmer Finbarr the previous weekend, river swimming in Fermoy in 7½º Celcius (45½F) water, in October. At the time of writing, I wrote that seemed too cold for me as a sudden transition  from sea swimming in 10º Celcius. And I had a few years of cold water swimming behind me already.

It made me feel like he’s good at cold and I’m not. But Finbarr is much taller than I, meaning an overall greater heat retention.  He is also exceptional in his ability. He swam 35 minutes in that temperature. I was seriously impressed. I’m sure it hurt him too though, just as much as a 10ºC (50F) hurt me then.

Finbarr's smile here belies the fact that his foot is planted on Liam Maher's neck underwater.
Finbarr’s smile here belies the fact that his foot is planted on Liam Maher’s neck. Underwater.

In 2013/2014, I don’t consider that exceptional, and regularly swim the same or longer in that temperature. Of course Finbarr is swimming an hour.

The first few times you immerse yourself in very cold water will provoke a fight-or-flight response, elevating heart rate and stress hormones, potentially leading to anxiety or even fear.

I saw this with a friend recently when we were going for a swim at around 7.5º C. He hadn’t been in cold water for a couple of months so he was very anxious beforehand. He was utterly fine during his swim and afterwards.

Habituation just means becoming accustomed. In our case become accustomed to getting in cold water. It only takes four to six repetitions before the pre-swim anxiety abates and your heart rate to stay controlled. It become easier. The pain of immersion will decrease, though never disappear, and cold shock response will also reduce somewhat. Indeed there are few physical activities from which we can have such a speedy response.

More importantly, is you will realise that it’s not going to kill you. All the pre-swim anxiety will start to diminish. That the pain is not what you anticipated, that your imagination is worse than the reality. That every time you experience that initial response, you are reducing the power that cold may have over you.

You will start to see Cold in a different way, as a more intangible ghost over which you also have power. Until you too are part of this cult.

Cold Shock Response and the Mammalian Diving Reflex in cold water swimming – Positive & Negative Feedback systems

I read a blog recently about cold immersion and cold baths, and cold swimming to a lesser extent. The author was speaking about the positive physical and mental benefits of regular ice baths. Similar benefits to what we as cold water swimmers regularly experience. All well and good. For aspirant Channel swimmers without access to regular cold water swimming, the recommendation for cold showers and baths is old and trusted.

However in his explanation of what was happening in the body the author focused exclusively on the Mammalian Diving Reflex as the primary response of the body when being immersed in cold water and completely ignored or didn’t understand the effect of Cold Shock Response and its place in the equation. (I didn’t save the blog link, sorry.)

That blog wasn’t the only place you see this. If you search on Mammalian Diving Reflex you will see it widely referred as the (only) process  in action when people are immersed or submerged in (cold) water. It’s a classic example of people taking all their knowledge from Wikipedia, because it seems the same Wikipedia core text is used all over the place.

I’ve covered both before and as a cold water swimmer, rather than someone sitting into a cool water bath, and I’ve focused as  much on Cold Shock Response, and the issue of Habituation, the process of getting used to getting into cold water, (not the process of staying in it).

The blog author just cut and pasted a Wikipedia article on Mammalian Diving Reflex, and while the Wikipedia article wasn’t wrong, both it and the blog were incomplete from the perspective of a  cold water swimmer.

So what are each of these and do they interact?

While swimming in Tramore Bay the other day, the water having risen by a degree in two weeks to about 7.5 Celsius, I got thinking about these two responses and how one, Cold Shock Response could be considered a positive feedback system while the Mammalian Diving Reflex could be considered a negative feedback system.

It’s not the first time I’ve wondered about Positive Feedback in a biological sense in open cold water swimming. Previously I considered that the Habituation/Acclimatisation process in cold water swimmers could also be a positive feedback system.

The simple process of improving cold ability
The simple process of improving cold ability

In Systems Theory (and elsewhere) a Positive Feedback System is where a small change causes a further bigger change. Therefore positive feedback is often considered a de-stabilising process. One example might be the international banking system that led to the 2008 collapse: Increased risks led to larger profits which led to larger risks until the system collapsed. However positive feedback can also be a process for change or improvement: If you swim more, you get fitter and able to swim even more, i.e. the training effect. Or the more you get in cold water, the better you get at getting into cold water.

Negative Feedback is often considered a stabilising process, the most common example is a thermostat which regulates heats by switching off when it gets too hot, switching on when it gets too cold: Negative Feedback acts in the opposite direction to the initial impulse.

Cold Shock Response is the bodies response to sudden cold water immersion. It results in varying degrees according to the person’s habituation experience, primarily in elevated heart rate, and elevated stress hormones. It is the elevated heart rate which is dangerous, to lesser extent in the increased chance of cardiac arrest, but more commonly in the chance of aspirating water due to shock and subsequently drowning. Less habituated or experienced swimmers will note an increased heart rate and nervousness even before immersion occurs if they are expecting the cold. I noted some years ago that the first time I ever swam during winter without a wet-suit, I was literally terrified beforehand. Then the initial cold shock drives the heart rate higher. This is a limited example of Positive Feedback, where the initial is destabilised by something (cold) that acts on the input.

The Mammalian Diving Reflex is another innate biological response to immersion. As the name implies all mammals exhibit this, human to weaker extent, but it exists to extend the time that animals can survive while submerged by reducing the need for respiration. This occurs in swimmers through two main biological reactions; decreasing heart rate (brachycardia) and therefore slowing the buildup of carbon dioxide in the body, (as excess carbon dioxide is what cause us to have to breathe); our constant companion, peripheral vaso-constriction, where the capillaries and blood flow in the extremities is restricted to allow more oxygenated blood to be available to the heart and brain.

The Mammalian Diving Reflex is initiated when the fact is submerged, and this is the reason I have previously written many times that you should splash your face before getting in the water, rather than the incorrect but widely cited slashing water down your back.

The Mammalian Diving Reflex is obviously a case of Negative Feedback, where the body reacts in opposition to submersion to protect itself.

So we can see that there is both positive and later negative feedback in operation in cold water swimming, where the negative feedback occurs to stabilise and protect a human through adaptive physiological response. But the initial negative feedback of Cold Shock is very significant and should not be ignores, as so many non-cold water writers seem to do, as it carries its own significant risk factor.

The bottom line though, is that this is another way of saying, that ability in cold water swimming improves with repetition. Habituation improves much more quickly than Acclimatization. In a little as four to five repeats, people become much more comfortable with getting into cold water.

Now get out there!

Cold Water Swimming Articles Index

Snow & Ice on the platform
Once you’ve swum during snow, you’re a true cold water swimmer

This post is an index with a very brief explanation of each of the specifically cold swimming related articles I’ve written, so one can scan the entire list for what is most relevant for their question or area of specific interest.

I was a bit surprised to see just how many I’ve written.

Articles sometimes tackle a similar area from a different angle, some focus on one small aspect of the cold-water swimming experience. This is a body of articles with which I’m quite happy.

If I could impart one simple message, it’s this:

Cold water swimming is dangerous, difficult and requires repetition to improve. No-one does it naturally or easily and knowledge is your ally.

By exploring the many aspects of cold; environmental, physiological and psychological, I hope to help you understand cold better and therefore become a more confident cold water swimmer. These articles therefore are intended to help swimmers adapt to cold water swimming.

It is really important to repeat that most of us are not naturally good at tolerating cold. (I certainly am not). Cold should be seen as something you train for, the same as any other aspect of your swimming.

The Ten Commandments of Cold Water Swimming. I am a prophet of cold water! :-)

The Golden Rules of Cold Water Swimming. For when Ten Commandments are too much.

Loneswimmer returns from the sea, with the commandments of cold water swimming
Loneswimmer returns from the sea, with the commandments of cold water swimming

Habituation. The process of getting used to getting into cold water. This is where it all starts and was therefore the first cold water swimming article I wrote.

Acclimatization. the process of developing tolerance for staying in cold water.

Introducing a Precise Open Water Temperature Scale. This site’s most popular article.

The Reverie of Cold. What I consider the best article on cold or maybe ever, that I’ve written.

“What temperature of water is too cold to swim in”. The most common search term leading into this site.

“What temperature of water is too cold to swim in” Redux. An updated version of the above post with a fuller list of factors affecting the answer.

I just can’t handle the cold“. Part 1Part 2 (What is the Vagus nerve and why is it important?), Part 3 (Fear). This is a phrase I hear a lot. Why this belief is irrelevant and why you, or I, are not special when it comes to cold.

WHY would anyone swim in cold water? Trying to answer the LEAST asked question about cold water swimming.

One of my hypothermia experiences. It happens to us all. That’s part of the deal.

Cold water and cold immersion shock, the first three minutes. It’s really important to understand what happens the body in the vital first few minutes of swimming in cold water.

The Worst Three Minutes. A not-often acknowledged aspect of cold water swimming.

How To: Prepare for cold water swim. Practical precautions around cold water swimming.

Prepare, Monitor, Recover. A short article on part of experienced cold water swimmers’ ethos.

Men, women and cold. Understanding gender differences in cold water exposure and tolerance.

Brown Fat vs. white fat. Interesting and very relevant recent scientific findings that have direct relevance to cold water swimmers.

Brown Fat. A revised version of the previous post.

Merino wool, my favourite cold weather clothes for per & post swimming.

The cumulative effective of cold water swimming. How it feels to swim in really cold water for many consecutive days.

Six hour swim in sub-eleven degree water. The second toughest swim I’ve ever done.

Christmas and New Year’s Day swim advice. Comprehensive advise for irregular swimmers in cold water. Applies to any irregular swims and swimmers.

coldExtreme Cold Water Adaptation in Humans. A five-part series trying to tease out all the various factors  of cold adaptation: Part 1 Asking the questions about individual variability, Part 2 (habituation and acclimatization), Part 3  (metabolic responses), Part 4 (further physiological responses), Part 5 (conclusion).

How we FEEL cold water. Concerning the body’s thermo-receptive response to cold water.

Always wear a belt. A lesson learned (and sometimes forgotten) about cold water swimming.

Peripheral vaso-constriction. The bodies primary physiological response to cold, in picture.

Wearing a watch. The primary safety device on cold water.

The important of stroke and the deficiencies of Total Immersion type swimming in cold water. Following the wrong advice for cold water is dangerous. Stroke rate is very important.

“Is the water too cold to swim”? Another different take on this popular question.

Winter. I like it. I hate it. The dichotomy of a cold water swimmer’s thoughts.

Come with me on this cold water swim. As close as I can take you to my experiences of swimming in cold water during the Irish winter.

Cold water swimming and the Second Law of Thermodynamics. Another experiential post of cold water swimming, with some musing.

Understanding the Claw. What is the Claw and why do cold water swimmers get it?

“Where did my Claw go?”  Further discussion on the Claw amongst experienced swimmers, the Claw being a common occurrence for cold water swimmers.

How To – Understanding Mild Hypothermia in swimmers. To address hypothermia, it is best to understand it. Mild hypothermia is more common than not amongst cold water swimmers.

How To – Understanding Moderate and Severe Hypothermia in swimmers. There’s nothing moderate about Moderate hypothermia.

How To – Diagnosing and addressing Moderate Hypothermia in swimmers. Understanding cold for support crew.

Speaking as a Coldologist… Analysing (and debunking) a claim to cold adaptation through meditation.

Cold water swimming and alcohol. They don’t mix and are a dangerous combination. This is important.

Ice Miles: My First Attempt, Part One (The swim). My First Attempt, Part Two (Post swim and analysis). My Second Attempt. Ciarán Byrne’s report of the successful Lough Iochtar Ice Mile.

What is Cold Water Diuresis in swimmers? Another physiological response to cold explained.

The relevance of shivering in cold water swimming. Yet another important to understand physiological response to cold.

The Magic Number. A consideration of transitional temperatures in cold water swimming.

Extreme cold adaptation in humans, part 3

Tiina Makinen‘s “Different types of cold adaptation in humans” works as a meta-analysis of various scientific studies of cold adaptation and is a fantastic read and is available at the Finnish Arctic Institute of Health.

 It ranges over types of cold adaptation, (physiological, genetic, behavioural), acclimation and acclimatization in specific groups (occupational, indigenous, high latitudes) and certain affecting factors. Some areas such as genetic adaptability in indigenous people aren’t relevant for swimming.

  The paper does a great job of rounding up the various effects of cold responses, I’ll only summarize the relevant swimming ones.

 She lists three main types of cold adaptation, metabolic, insulative, hypothermic, with three physiological responses to each one.

 

Figure one displays generally how these arise.

For most of us, we fall into the body heat loss category due to swimming time. (However for short term experienced winter swimmers, I believe we can enter into the cold habituation category of blunted shivering, due to my experiences this winter, where I had little shivering or shaking).

 So this brings us the point that Finbarr made in the comments to the first post of this category, where he said we generate more heat, which is known as thermogenesis.

 Anyone who has read Lynne Cox’s Swimming To Antarctica may remember that on testing in controlled conditions (acclimation) she actually increased metabolic heat production. I seem to recall some other people testing at this also, but can’t find studies right now.

The body is evolved to protect against a certain amount of cold by increasing heat. But thermogenesis is normally achieved by shivering, and to do this in air, not water. For swimmers therefore shivering is not good. But it’s still possible to increase heat (non-shivering thermogenesis, NST) through other methods.

 As adapted swimmers we do this in two main ways:

1: Peripheral vasoconstriction, which we are all familiar with. The blood flow to the skin is reduced, retaining more heat by not dissipating heat from a higher blood flow through the skin & limbs. Again, from personal experience, Dee has noticed how much and how quickly my skin cools on even short swims, when I feel completely comfortable. Many of you will recognise this as a clammyness to the skin, but since your hands are also cold, you can’t really feel it. This is what Makinen calls an insulative response.

2: The second response, and we don’t think of it as response, since it’s the start of the process that leads to hypothermia, is Insulative-Hypothemic. In this our skin temperature reduces…as does the core temperature. Obviously unchecked, staying in cold water long enough, leads to a strictly hypothermic response (you get hypothermia).

So as an experienced cold water swimmer, you are autonomically working on both these factors (amongst others more consciously).

Table one gives the expanded responses available.

Makinen also talks about purely Insulative adaptation. From our point of view however, I like to think of this one as a more conscious response. Sometimes, we put on more body weight deliberately. It’s a toll available to all swimmers. More weigh, as I’ve said previously, equals more surface area equals slower heat loss.

 Makinen makes brief reference to brown adipose tissue, brown fat, which I’ve mentioned previously. Here I’m going to personal observation. I noticed over the course of last year, that Rob, Gábor, Ciarán, and myself put on more weight particularly across our upper backs once we were in regular sea training. Jen, being female had a more whole body subcutaneous effect, but also had the morphologically changed upper back, while Liam had less time to adapt to cold than the rest of us because of his earlier swim date, and I couldn’t see up that high anyway.  Other anecdotes within the Irish Open Water group indicate that this happens with regular exposure. Studies in the New England Journal of Medicine showed brown fat developed quickly after repeated cold exposure. Makinen notes that it is more likely in women than men, but those studies were in temperature reduced air, rather than water.

The sites of brown fat growth are significantly in the upper back! Also , brown fat is metabolically active, unlike white fat, so it will generate heat.

And despite a reasonable training amount since, at least for Gábor and I, we’ve lost that enhanced upper back/shoulders, which I think is because, though we swim weekly, we are not in often enough to necessitate brown fat, which would return once more regular cold water training would recommence.

So we a source of metabolic thermogenesis to which Makinen doesn’t much refer, as part of my hypothesis. #

Did I mention my hypothesis? So yes, I have one. It’s nothing extraordinary but I’ll come to it.