Tag Archives: Cold Habituation

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.