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We’ve partnered with leading cold water scientist, Dr Heather Massey to bring you the truth about what happens when you cold water swim. We’ve looked at all the benefits, ‘advice’ and science around what (really) happens to bodies when immersed in cold water.

This article is some considered advice for YOU, to allow you to #SwimYourOWNswim

The problem is that any “advice” is seldom specific enough to YOU.

We’ve seen a rise in ‘advice’ being given out, most of it anecdotal rather than based on science or fact. That’s OK if this advice is delivered using the phrase, “For me this works the best”, or something similar.  But what we see on many social media forums is someone saying “Do this or try ….”. Multiply that by the number of outdoor swimmers and that is a lot of ‘advice’. We know that it is meant in good faith but regularly the advice is conflicting. And never specific to YOU … how can it be? We’re all different!

So let’s make the information specific to YOU

We have broken this article up into four sections:

1. Cold Shock & Hypothermia 
2. Before your swim
3. During your swim
4. After your swim

Our aim is to arm YOU with all the science and knowledge for you to make your own choices that are right for you on that day.

1. Cold shock & Hypothermia 

When in cold water, the science here is that our bodies cool from the outside in, starting with the skin cooling, then onto superficial nerve and muscle cooling then finally onto deep tissue cooling otherwise known as your core.

So in terms of the cold shock response, this is mainly felt in the first 30 seconds to 2 minutes of being immersed in the cold water – skin cooling.

What happens here with the cold shock is that your body responds to that cold stimulus. The response results in high concentrations of stress hormones including cortisol, and adrenaline. These hormones are fast responding and prepare the body for ‘fight or flight’. This isn’t a response which supports the body to regulate our temperature, but ensures our body is prepared for the new cold environment we are in. In addition to the stress hormones, as the cold shock subsides we also release endorphins and serotonin which stabiles mood and increases feelings of happiness. It is this combination of hormones and others which gives us that ‘post swim high’, that feeling of euphoria after you exercise.

And then hypothermia sets in once you cool through the skin, muscles, nerves and finally to the deep tissue.

How quickly you go from one layer to the next depends on many things.

Now we will break it down into how you can best manage YOUR cold water swim.

2. Before your swim

How long should I stay in? Length of time is not the answer: it’s how YOU feel remember to #SwimYourOWNswim. Here are some of the questions that you should be asking yourself each time you for a cold water swim;

• How much experience have you had?
• What’s your body type?
• Will you be in skins or a wetsuit? (If you are skinny and lean with no fat you will cool quicker than someone with more insulation or wearing a wetsuit.)
• Have you slept well?
• Are you stressed?
• When was the last time you ate?
• Are you hydrated?
• Are you on your period?
• Are you perimenopausal or going through menopause?
• What’s the air temperature?
• What’s the water temperature?
• What’s the wind chill like?
• How far away from the water is your kit?

All these questions are questions you should be asking yourself before you go to every open water swim. You may find it easier to have this list of questions handy on your phone or keep a diary.

The outcome of these questions will be different every single time which is why it’s much better to get to know your own body really well, and figure out what YOUR triggers are to getting too cold. This isn’t an overnight process; it takes time and is best done in stages throughout your winter swimming experience.

This is why using the current fad of “1 minute per degree” can be so dangerous!

Whilst the thought process behind this is in some ways valid (that the colder the water, the shorter the swim duration should be), quite often a time limit is treated as a goal to be attained or broken!

That “rule” may be too long for an individual, depending on the answers a person gives to the questions above. And that could lead to a dangerous situation.

The Focus of your session

One thing to think about when you’re deciding how long is the correct length of time for YOU on that day, is to focus on the experience you want to gain from your swim.

• Is it to get fit?
• Or get that famous post-swim high?

If the latter, then actually, that feeling is best achieved by a quick dip! Scientists believe (but have not yet proven), that the post-swim high occurs as a result of the initial responses to the cold water. So as soon as that gasp and any elevated breathing has passed, you could have a quick swim or simply get out.

(Instead of staying in for a long period of time, leading to you being poorly coordinated and hypothermic, = very cold and not very happy).

Wetsuit

We still get the cold shock response when wearing a wetsuit. So if wearing a wetsuit gives you the confidence to get in the water, keep wearing it. You may be able to stay a little longer, but bear in mind the focus of your winter swimming session.

Fuel yourself

It’s a good idea to ensure you have fuelled yourself properly before a cold swim to ensure your body has adequate carbohydrates to fuel the shivering after your swim. (More about this later.)

Or don’t swim today

Don’t feel the pressure of having to swim just because someone said you should! Don’t treat a swim as a game of ‘chicken’, just because one person is staying in longer doesn’t mean you should.

Ego has no place in cold-water swimming. #SwimYourOWNswim

3. DURING YOUR SWIM

If you are just starting out your cold water journey – start small, with a really short dip. On top of the questions you’ve asked yourself before getting in, these are some more good questions to ask yourself about that day specifically;

• Am I swimming with people who have similar goals to me?
• Do they have a similar level of experience?
• Are they a similar size and shape, wearing a wetsuit or not?
• What is the temperature of the water and air?
• What are the conditions on the day like?

If you can keep track of how you feel before getting in and add that to the conditions on the day you might be able to start figuring out what your body can and can’t tolerate. Everybody is different and everyone has different cold water triggers:

• the ‘phantom’ finger
• the claw hand
• the white toe
• The ice nose.

This is how varied the responses can be! The only way you will find out your trigger is to keep track of your body and what happens.

4. AFTER YOUR SWIM

Warming up slowly is better than warming up quickly.

The main thing to focus on when trying to figure out how quickly to warm up is to think about how much your body has cooled in the process – have you just cooled the skin or have you cooled to your core? If you have cooled to your core then the rewarming process becomes INCREDIBLY important.

Cool Skin or Core Cooling

You will have seen photos and videos of people running from hot saunas to ice holes and running back to the sauna. So why shouldn’t we have a hot shower when we get out or jump into a steam room (if you have that luxury)? Well this again totally depends on the circumstances. If you are just ‘dipping’ then you might be able to get away with a warm shower or sauna after your dip as your body won’t have started the deep cool.

There is a myth running around about ‘after drop’ and if you step into hot showers you might shock the body too quickly when the cold blood mixes with the warm blood but this isn’t true. Watch cold-water experts Professor Mike Tipton and Dr Heather Massey (yes the very same Dr who is contributing to this article!) explaining it here in this incredible webinar. About 40 minutes in is where this is explained, but the whole webinar is well worth a listen!

Essentially they are saying that the myth around “after drop” relating to blood flow is not in fact true. “After drop” refers to the fact that your core continues to cool when you leave the water as the (muscle) tissue of the body is colder. The core cooling slows and is reversed only when we insulate our bodies from the cold and generate heat that warms the tissue. All of this takes a bit of time to occur after your swim.  The issue with warming up too quickly, as in warm showers, is that you trick your mind into thinking you are warm. The skin is warmed by the shower and this in-turn stops the shivering process, but your core temperature is still cooling for some time.  When you leave the shower and the skin is cooled slightly you will begin to shiver again. So unless you have a thermometer deep within your core to test your temperature and monitor rewarming then if you have gone into deep body cooling, it’s not advisable to have a warm or hot shower.

If you think here about when you defrost a chicken breast in the microwave, if you do it too quickly then you will start to cook the outside before the centre has defrosted, it’s still rock solid. This is what happens to the body when the skin is warmed, but the core has not been warmed.

Get dressed!

It’s best to get dressed as soon as possible into lots and lots of layers, each layer trapping warm air to help aid the rewarming process. Using big jackets on the top, woolly hats, thick socks and gloves will help to rewarm a swimmer in the safest way.

And remember shivering is totally normal and actually vital in order to warm our bodies up.

Shivering

Shivering is our body’s natural response when we get cold. Shivering is one of the hardest forms of exercise and requires a lot of energy to do so. If you have cooled your body to the core or if shivering is uncontrollable it can make you really tired! Shivering prevents further cooling and helps to rewarm the body from the inside out. Like any exercise you need carbohydrates or sugar to fuel that process. The quickest and easiest way to get sugar into your system is through liquid form, so a sugary coffee, tea or hot chocolate is the ideal source of fuel for your body to help warm itself up. Washing it down with a nice piece of cake helps too. But like we said earlier it’s also a good idea to make sure your body is properly fueled before getting in too.

Warm drinks are better than hot drinks

This question has been debated on many forums. And is something about which we ourselves have been educated recently, thanks to Dr Heather! The current thinking around why warm or hot drinks are useful is because many people think that these drinks can help to rewarm a swimmer. This is in fact not entirely true.

Firstly, what’s hot for one person is different to someone else. If you are used to drinking piping hot tea then you might be able to handle your drinks hotter than someone that drinks coffee with lots of milk which is generally cooler.

That being said, Dr Heather Massey and Mike Tipton have done some calculations on this topic.

Does a warm/hot drink aid the rewarming process?

The conclusion to the work of Heather & Mike is pretty interesting. Humans are made up of 80% liquid (water) and if you add 1 flask full of warm water (500ml) to roughly 60-80kg of water the temperature of the water rises by about around 0.1 degree – that’s hardly going to warm you up but what is can do is help to reduce the rate of cooling due to after drop. So there is a slight benefit.

The main functions of drinking something warm is to add fuel to your body to overcome the energy lost through shivering and to reverse the dehydration caused by the cold water.

A post swim drink can make us feel better. There’s a real sense of comfort when wrapping your cold hands around a warm flask while chatting to your friends about your swim.

One of the reasons we specifically say warm not hot is because if you are cold and you’ve been swimming for a while you can spill your drink if shivering uncontrollably, which could lead to burns. Also if you need fuel in your system fast, a warm drink is the quickest and safest way to achieve this. It might even be a good idea to ensure you have fuelled yourself properly before a cold swim to ensure your body has adequate carbohydrates to fuel the shivering after your swim.

Dehydration

Being in cold water increases urine production and results in dehydration on rewarming.

This is a bit odd, normally our body produces urine to remove excess water, not to deliberately dehydrate us. But cold-water causes the blood vessels close to the skin to constrict and results in a redistribution of the blood from the skin to the core. The body senses this ‘excess’ fluid in the core and stimulates urine production. But when we start to rewarm and the skin blood vessels open up, we have a smaller blood volume and so are in a dehydrated state, so having a drink after your swim is a start rehydrating after your swim.

So all that’s left to cover is something we have seen many times in different cold water swimming forums;

Sometimes I feel so tired after a cold swim and sometimes I feel alive and full of energy.

This depends on how much you have cooled your body and how much shivering you have required.

Cool Skin

If you have only taken a very quick dip, then you might have just cooled the top layers of skin, maybe only just long enough to overcome the cold shock response our bodies feel when getting into cold water. If you get out and dress quickly you might not even start the shivering process but as stated above – you will have all the feels of that post swim high!

Core Cooling

Swimming for long periods of time can result in core cooling. If you reach the point where you start to shiver (as discussed earlier) you may feel quite tired. Shivering produces a lot of heat, to do so requires a lot of energy, but if you don’t fuel your shivering with some sort of carbohydrates then you will feel even more tired! Which is why it’s handy to have a warm flask of hot chocolate or sugary coffee to drink as this is the fastest way to get those carbohydrates into your system.

This might be the reason why some people feel really tired swimming, yet some people feel euphoric or “more alive” when they swim in the cold water – how cold has your body become?

Our main conclusion is to focus on YOU and #swimyourOWNswim

We wanted to say a huge thank you to Dr Heather Massey for her amazing insights into the article and all the science! We also want to say another huge thank you the very talented Gilly McArthur for the amazing illustrations.