Is it healthy to take a cold dip in winter? Is it true that most heat loss occurs through the head, and can we get ill if our legs get cold? Here is a summary of our researcher’s answers.
In recent years, winter bathing has become very popular. Enthusiasts believe that it is good for the immune system and helps to clear the head. Detractors say that the cold simply make us ill.
So, what do researchers have to say about the effects of cold on our bodies? Gemini invited SINTEF research scientist, physiologist and low temperature expert Øystein Wiggen to share his knowledge about the cold.
“What do we know really about the health effects of cold bathing?”
“Significantly more research has been carried out into the detrimental aspects of ice baths rather than their potential benefits, so we have to tread carefully when it comes to any definitive conclusions”, says Wiggen. “But ice baths seem to have many positive benefits.
There is evidence that an ice bath can help to better equip the immune system against potential threats, and in so doing offer a positive effect. Beyond that, research shows that bathing in cold water can actually be beneficial for chronic joint inflammation, among others.
One theory is based on the idea that the vagus nerve plays a key role in our bodies’ responses to infection, and that exposing the body to cold water can in fact be a simple way of stimulating this nerve. We anticipate that more research will be carried out in this area in the future”, he says.
“Is it true that ice baths help our bodies recover?”
“Yes”, says Wiggen. “It is thought that the combination of the low temperature and water pressure results in a positive effect. It’s like putting on a cooling compression stocking. Research here concurs that ice baths reduce perceived muscle stiffness and promote more effective recovery.
A further benefit of exposure to cold is the increased activation of brown fat. Brown fat is made up of fat cells that burn calories which produces heat that helps to maintain body temperature. Any increase in brown fat activity may offer many benefits and this is another field that needs more future research.
But remember – you have to take ice baths regularly in order to get the most out of them. Just as with training in general, you won’t get many health benefits from just a single run or by taking an ice bath just once in a while”, he says.
“How important is it really to wear a hat when out in the cold?”
“The myth that most heat loss from the body occurs through the head is exactly that”, says Wiggen. “Heat loss is all about insulation and is greatest wherever the skin is exposed. So, in general, it’s not true that any given part of the body releases more heat than any other part. But our sensitivity varies. We experience the same external temperature entirely differently though our fingers than we do through our legs. Our fingers will always feel the coldest even though they are not. Having said that, it’s still a good idea to wear a hat to keep warm.
It’s also useful to know that our thighs and lower legs are less sensitive to cold than other parts of the body.
This is why many people think that it’s okay to wear a thick jacket, but with thin jeans and even no socks. But with lower body clothing such as this, our legs will account for more than half of our bodies’ total heat loss. So, if you want to avoid freezing when it’s really cold, you’ll get “more for your money” wearing long johns rather than an extra woollen undershirt”, he says.
Facts about SINTEF’s ‘cold lab’:
Photo: Thor Nielsen
SINTEF’s occupational physiology laboratory can recreate the harshest conditions imaginable. The so-called ‘cold lab’ is equipped with the following:
- Three different controlled climate rooms (hot, cold and a water pool)
- The temperature can be varied from -30°C to +50°C
- Air humidity can be regulated from 10% to 90%
- Wind velocities can be simulated to up to 22m/s
- Key physiological research tools include methods for measuring oxygen intake, body temperature, muscle activity and lung function.
- The lab has equipment to measure performance indicators such as power, endurance, muscle activity, as well as manual and cognitive performance capabilities under different climatic conditions.
- Modelling experiments can be carried out using a thermal manikin (a doll-like model fitted with a variety of sensors that simulate the human body).
“Do thin people get colder more quickly than those with a little more meat on their bones?”
“Fat is a good insulator”, says Wiggen. “Among other animals, it’s very clear that fat layers are developed more thickly in winter than in summer. Smaller, thinner, people have a large surface area relative to their body mass compared with bigger, more thickset people. This means that they lose heat and feel the cold more easily than those who are chubbier. It’s particularly important to remember this when you’re out in cold weather with small children. They will get cold more quickly than grown-ups”, he says.
“Can you get ill if you have cold feet?”
“There’s no evidence to suggest that this is true”, says Wiggen. “However, recent studies have indicated that cold air weakens the immune system. This happens when the cells in our noses, which are designed to protect us against viruses and bacteria, are weakened by the cold, making it easier for infections to take hold. It is also easier to catch infections if there are many people gathered together indoors, such as on a bus. However, there’s no doubt that it is particularly uncomfortable to have cold feet, and I can offer some advice for those who want to keep their toes warm”, he says.
“The first thing to do to keep your feet warm is to make sure that they are completely dry”, says Wiggen. “Water conducts heat 25 times faster than air, which is by far the best insulator. For many centuries, the Sami people kept their feet warm by filling their moccasins with a grass called bladder, or blister, sedge. This offers not only warmth but also absorbs moisture. For the more urbane among you, an old piece of advice is to line the soles of your winter shoes with newspaper. I often use this trick in combination with woollen insoles. It’s very inexpensive and I often carry some extra newspaper insoles around with me in case I have to replace them while I’m out walking. Their wearability is just about okay”, he says.
“If you want to avoid freezing when it’s really cold, you’ll get “more for your money” wearing long johns rather than an extra woollen undershirt.
“Do you have any advice for keeping our fingers warm?”
“Yes”, says Wiggen. “There’s one simple thing you can do if your fingers are cold starting out on a skiing trip. When we start to get physically active, the body first sends blood to the major muscle groups that have the greatest need of oxygen. When these are warmed up, but your fingers continue to be very cold, it can be a good idea to stop for a while because this causes the blood to transport surplus heat to our skin and fingers. So, let your arms drop and use centrifugal force to get the warmth to your fingertips even faster”, he says.
“When do we become so cold that it becomes dangerous?
“The body has several mechanisms for warning us against this”, says Wiggen. “When we get very cold, we instinctively start shivering as a means of maintaining our body temperature. If our core temperature falls by two degrees, this shivering mechanism reaches its peak. This is a serious situation, which fortunately only very few of us ever experience. But we all know what it’s like to have cold skin. When our skin temperature drops below 15°C, most of us will start to feel pain and major discomfort. I’m not just talking about that painful tingling in your fingertips, which simply means that you’re getting the warmth back into your fingers. When the temperature in our fingers falls below 10°C, things are really getting more dangerous. They become numb and the risk of hypothermia and frost injury increases significantly. If this starts to happen it’s important to get warm as fast as you can. Go indoors or increase your levels of activity to the extent that you can feel that your body is producing the heat you need to keep itself warm”, he says.
“What do we do if we’re unlucky enough to fall into an icy river or lake?”
“The first thing that happens is that you panic and the body goes into shock”, says Wiggen. “After a minute or two, you’ll start to hyperventilate. At this stage, the most important thing is to keep afloat and avoid swallowing any water. You will drown if you take in too much water. After a while, your breathing will normalise. Now is the time to act before you lose the strength in your muscles. You must now use all the strength you have to get your body out onto the ice. If you fail to get fully out, it’s still important to get as much of your upper body as possible out of the water and out onto the ice. If you manage this, the cold will actually help you. Many people have survived because they’ve become frozen to the ice, which actually saved them from drowning”, he says.
“If you enjoy skiing or cycling in winter, it’s useful to know that when the temperature falls close to minus 20, there’s an increased risk of getting frostbite on exposed skin such as your face”, says Wiggen.
“The combination of cold and wind can result in frostbite after as little as ten minutes exposure, so make sure that your face is protected. If you’re taking part in high intensity activities, it’s important to protect your airways. Cold and dry air can be challenging for asthmatics or persons with sensitive airways”, says Wiggen.
“What is the quickest way of getting warm once you’ve become so cold that you’re suffering from hypothermia?
“This will depend on what you have available, but a good rule of thumb is to have a hot shower, followed by a hot drink”, says Wiggen. “If you don’t have a shower available, the best thing is simply to get your body moving. It’s amazing how warm you can become with just a few arm lifts or by jumping on the spot. Damp underwear will cause unnecessarily high levels of heat loss, so it’s important to change into some dry clothes. And it’s always a good idea to have a change of dry woollen underwear in your rucksack”, he says.
“They say that wool is the only material that really provides insulation from the cold. Is this true, and if so, why and to what extent?”
“Wool is excellent because it insulates even when it becomes wet”, says Wiggen. “But some synthetic fibres are better than wool at wicking moisture from the body, and thus dry more quickly while you’re wearing them. There are currently many hybrid textiles on the market made of both wool and synthetic materials that attempt to achieve the best of both worlds. What suits you best will depend on your levels of activity and personal preference, and whether you have the opportunity to change into dry clothes when your activity is completed”, he says.
“And finally, why do we want to pee more often when it gets cold?
“This is an entirely natural physiological response”, says Wiggen. “The cold makes the blood vessels in our skin and extremities contract in order to reduce heat loss. This increases the volume of blood in the body core. The body responds to this by releasing more fluid via the kidneys, making you want to pee”, he says.
This article has been updated to include facts related to cold bathing. The first version was published in Norwegian on 2 March 2018.