Tag Archives: cold adaptation

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 5

All right , let’s finally wind this down with an obligatory reminder from Tiina Makinen; “several individual factors effect the rates at which people respond to the same stimuli . The time course of adaptation is dependent on the threshold of the stimulus, a latency period, the physiologically and possible genetically determined maximum of an effector organ, the speed of tissue/organ/systemic adaptation”., which of course means everyone is different.

 There’s a nice chart of all of this, (because I think you know by now that I like charts). Though without a time scale axis the chart implies that pre-adaptation and adaptation decay take the same time.


 There’s some brief mention of health effects of cold adaptation, but that’s a different subject than what we’re pursuing here, too many non-similar studies without controls and for another time anyway.

 Also, and you can judge for yourselves on this, the studies seem to imply a two stage-process, pre-adaptation and adaptation. Which is fine for a study, but we know it’s not like that, as the chart shows.

 So the hypothesis is: Cold swimming ability is an iterative incremental positive feedback process (limited).(In a negative feedback process, a change one way directs a change in the opposite direction, (like a thermostat). It’s a regulatory process that stabilises. In positive feedback a change generates further change in the same direction, usually leading to destabilisation or enforcement).

The process of improving cold ability

 Simply, you improve habituation so you improve acclimatisation, which prompts you to return and your habituation improves further, making it easier again to become immersed, and so on. Or maybe one could just simply say, small improvements happen fairly quickly, these accumulate and allow you to improve more, so long as you keep exposing yourself to cold.

 Disclaimer. I never thought this would be so long! But it didn’t know it would be so much fun to write either.

Extreme cold adaptation in humans, part 4

So we’ve covered a lot of the features of cold adaptation.

 One major factor of habituation is left, and it’s key. Let me quote directly from Makinen. All subsequent italicized sections are direct quotations: “Young [] postulates that the type of cold adaptation response is dependent on the amount of cooling of the body ”.

Though further,…“habituation is the most common form of cold adaptation and develops in response to repeated cold exposures where whole-body cooling is not substantial. When being habituated to cold, thermal cold sensations are less intense and shivering and the vasoconstrictor response is blunted.

This is what we realise though. Habituation is about the initial immersion process for us. This is saying that the overall perceived pain of the immersion process lessens.

Now we come to what I think is far more relevant for us swimmers than the weight it is given in the paper: “At the same time stress responses are reduced, meaning a lesser rise in blood pressure (BP) and reduced release of stress hormones in the circulation.

This was, for me, the missing piece of information. It explains for example why this winter I could get into 5 C water with little discomfort. I now have, to use the terminology, blunted response to cold. My gasp reflex is almost gone, my heart rate stays pretty normal prior to getting in, and even as I get in. I’ve mentioned in other posts this winter that this year I am better than I was last year, and last year I was better than the year before.

And the paper agrees: “The initial response to immersion to cold water involves a “cold chock” (sic) response associated with hyperventilation, tachycardia and a reduced breath holding time”.

Now the paper does say that this doesn’t seem important to extended exposure. Nevertheless, it seems to me that the more comfortable you are initially, that would translate into a certain extension of duration ability.

A very important point that tangentially validates some of what we say, (and I think I said in previous posts): “Furthermore, habituation to cold (five immersions for 2.5 min in 12°C water) increases breath holding time, and was not augmented by psychological training”.

So it’s purely physiological. Psyching-up routines are unnecessary (though personally I do like to take a few seconds of seeking calm before entry), but the important part there is the five immersions.

Continuing: “It has also been demonstrated that repeated immersions in cold water result in a long-lasting (7-14 months) reduction in the magnitude of the cold shock response. The precise pathways and mechanisms behind habituation are not well understood, but could occur at the spinal cord or the higher centres of [the Central Nervous System].

 This is completely at odds with what I said earlier, and what we swimmers believe to be true, that losing the hardening process happens four to five times quicker than actual hardening. It could be that many us of don’t want to experiment in this area by losing all the hard work.

 Insulative and metabolic-insulative physiological adaptations occur “when repeated exposures to cold cause significant heat loss. Insulative adaptation to cold is believed to develop when [metabolic heat production] is insufficient to prevent cooling of the core”.

 “Very brief repeated whole body immersions (20 s) to cold water (0-2°C) causes habituation of thermal sensation and comfort already after the first exposure “. So habituation improves immediately. I had put this down partly (and obviously incorrectly) to a partly psychological knowledge that well, it didn’t kill me the first time.

Winter swimming results in a suppressed [metabolic heat production] and heart rate in response to cold . […] Regular winter swimming also attenuates the catecholamine response to cold water [...] A follow-up study of winter swimmers over the swimming season observed a decreased BP and catecholamine responses in the end of the winter.

But with this important caveat: “However, the response was similar in controls, suggesting either habituation to the research situation itself or seasonal adaptation.

 In the area of acclimatisation: “Longer periods of winter swimming (1 h at 13°C water) elicit a hypothermic response (lowered threshold) and delayed onset of shivering .

 “Whole-body immersion of longer durations (90 min to 3 h) into cold water (10-18°C) causes insulative or metabolic insulative acclimation ”.

 It goes on “Bittel [] detected similar thermal responses, but also an enhanced [metabolic heat production] after the acclimation, suggesting metabolic acclimation”.

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.

Extreme cold adaptation in humans, part 2

Brave swimmer (13 degree celsius)
Image by aryel_bc via Flickr

Let’s back up a bit. Waay back in fact, to some of my first posts, where I talked about Habituation and Acclimatization.

By the way, if I was writing those posts now, since my experience had changed again, I would have different figures. It’s good that I can still see progression from there, because for those of you whoare maybe further behind on the curve, or further ahead, we can all be assured that we are on the same relative learning curve.

For a quick recap, habituation is the learned process (for our purposes) of getting used to getting into cold water.

Habituation doesn’t necessarily mean you get better at it (though it is fairly inevitable). It just means you get more used to doing it (not quite semantic difference). So you know that it’s not really going to kill you, and the pain is transient, therefore you don’t have to fight yourself quite as much to go or to get in the water.

Acclimatisation is the process of becoming used to and better at, staying in cold water. Therefore they are two quite separate processes. (It’s not acclimation by the way, since it happens in the natural environment.)

One can also see back those posts I was asking “how can Thought affect your cooling rate?”, which is your ability in cold water. I obviously used a capitalised word to indicate directed mentation toward the specific end of extending time spent swimming.

Over the past year and half I’ve indicated all (I think) of the pertinent environmental and physiological contributors.

So let’s set most of those aside (weather, health, diet).

Swimmers call the process of getting better at cold water hardening. Here’s some experiental data from swimmers about the hardening process: You can lose it four to five times quicker than you gain it. Sorry to start at the end but it’s because we can at least quantify it a bit better.

Going back to the start though, and what I tell people who ask me, is that you see a definite improvement in your short-term in-water experience within about five swims, in any particular lower temperature range. So if you start at 12 C, you will see the improvement there, whereas someone who starts at 10C should see a similar improvement.

Some people I’ve talked to starting off, separate from the not-insignificant initial problem of just immersing the face, found it difficult to impossible to hold their face in the water for more than four or five minutes, in what I would consider warmish water (12C). Others found pain in the hands and/or feet to be the issues, some find the desperate gasping for air to be the worst aspect. Some have many or all of these symptoms to varying degrees.

In fact, writing it all down like that makes you wonder why on earth we would ever voluntarily subject ourselves to it?

Also, a reminder, don’t look at someone heavier and assume it’s easier for them, a common mistake. A heavier person has greater volume so retains heat longer, but the initial pain will be just as intense.

So, we levelled the field and we’re back to the initial question: take me and someone else approximately similar measurements, standing on the Guillamenes platform in mid February about to get into the water. And assuming I have more experience I will be out later. Why?

I had not planned to leave you hanging here, it just turns out that as I write this, in this format, it is taking more than I initially realised, that I can pull in others factors to do a more comprehensive essay on the subject.

Extreme cold adaptation in humans, part 1.

It’s spring. We’re in the sea more or want to be, stretching out swimming times or wanting to. It’s probably more appropriate to talk about cold now than during the winter, because we are coming into the most difficult time of year for distance swimmers.

In the winter many stop sea swimming or switch to wetsuits. Those of us who keep swimming skin through the winter do it for the challenge, and only think about relatively short exposure times.

This is following a discussion on USMS time back. American swimmer Mike N_ (Hi Mike!), who  engaged in a fantastic Open Water swimming holiday around Britain and Ireland…in January (crazy man)… directed me to a great paper on extreme cold adaptation in humans.

At various monthly meetings with Eilís for both of my Channel visits, and much to the annoyance of others swimmers wondering when I’d ever shut up (remember the recent introversion points), and going back further to my early days open water swimming, I kept coming up against one question no-one could really answer for me.

All things being equal, especially body size and insulation, why can one person stay longer in cold water than another?

Everyone prevaricates and says “experience”. I say why? They say “mentality”. Why? “Personal strategy”. Explains nothing really.

(Personal strategy is what I could call something like “I tell myself it’s warm“).

These were insufficient answers for me. Yep, geek. I wanted to know. Had the answer been something reasonable I would have forgotten about it. And remember, long swims in cold water, with that personality I mentioned the other day? Well, it’s hard to think about girls in bikinis on your tenth cold lap of Sandycove.

Here was my thinking: Think of a human as a “blackbody”. A blackbody is a physical method of simplifying calculation problems. Instead of dealing with a complex shape like the human body, think of it as a sphere. (It’s where physicist jokes about spheroid chickens in a vacuum*  come from. Those are funny jokes by the way, just in case you are wondering).

So treat two people who are roughly the same size and weight as a sphere. Their surface area is the same so surface area to volume ratio is the same.

Let’s say they have around the same fat percentage. And that the water temperature is the same.

So we have similar figures which should all give a measurement of heat loss: The amount of heat loss of a sphere is directly proportional to surface to volume ratio (large bodies lose heat more slowly than small bodies. It’s why polar bears and some sea swimmers are big).

The rate will also be directly proportional to the temperature difference between the medium and the body. Heat loss will be mediated by insulation properties (fat).

Now setting aside the fact that there is little research that I could find in this area (but not none) predicting heat loss in humans (I even logged a question into the Wolfram Alpha forums), we have a hypothesis: heat loss in water is directly related to a short list of physical factors.

Here’s another way of looking at the same problem with which you’ll be more familiar. New or For Sale houses now in Ireland require a new Energy Rating. That figure gives how well the house performs from a heat loss point of view. If you combine this figure with the number of Degree Days (number of days in Ireland which the temperature is below 15.5C when you want the internal heat to be 18C) you can come up with an equivalent estimate for heating costs over a year, regardless of house shape.

But we can see that the issue of duration in cold water is not answered by treating people as a black-body radiation problem.

(If it was possible, I probably would have an answer to my Wolfram Alpha question, and we would have simple swimmer charts which say if you weigh W, have X body fat percentage, then your exposure duration in X degrees of water would be Y time.)

Something therefore must have been missing from my visualisation. Computer or calculation models are derived by coming up a certain set of basic principles, inputting some real world measurements, and seeing if the output mirrors the real world.

What did I not consider?

An answer is in the next post on this subject.

*A farmer noticed that his chickens were sick, and called in a biologist, a chemist, and a physicist to help diagnose the problem. The biologist observed the chickens, concluding,I can tell you there’s something wrong with your chickens, but I don’t know what’s causing it.” The chemist took fluid samples from the chickens back to his lab, and returned saying, “I can tell you what’s infecting your chickens, but I don’t know how they got it.” Meanwhile, the physicist had been sitting on the floor, scribbling madly on several notebooks worth of paper. Suddenly, he jumped up, exclaiming, “I have the answer, but it only works for spherical chickens in a vacuum.