In recent years, winter swimming has become more and more popular. But is it really as good for health as they say? Bu Belhage, a professor at the University of Copenhagen, who researched the effect of winter swimming on the body, answers the question of Wiedenskub. Experienced walruses do feel healthier and get sick less often, but swimming in ice-cold water can cause shock.
Cold, dark and hostile to humans. In the winter months the sea almost screams at you: stay away!
Nevertheless, in Denmark there are about 25 thousand walruses who swim in an organized way, distributed among more than 93 clubs, and there are still many who swim in winter without entering any clubs. This is reported by the Bathing Safety Council.
Winter swimming has attracted a lot of attention in recent years, and our reader Camilla Engel Lemser asked us for a scientific explanation of what happens when we swim in winter.
“Thank you for being there - it's a pleasure to read you. Would you write something about winter swimming? The effect on the body, interesting research or something else that you can find …”, - she wrote in an email.
Winter swimming - shock therapy
We referred this question to Dr. Bo Belhage, professor at Copenhagen University. He himself is engaged in winter swimming and, together with three colleagues, investigated the effect of winter swimming on the body.
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Taking a dip in ice water is, in short, shock therapy, Bu Belhage said.
The body quickly cools and the body's defenses begin to work hard. The blood vessels contract, and the shock in the blood produces a cocktail of endorphins and adrenaline.
Surprising results from winter swimming research
But the effect depends on whether you are an experienced walrus or have never tried it before.
In an experiment, Boo Belhage and colleagues compared the reactions of 16 volunteers to their first winter swimming experience.
Participants spent one minute in an ice water bath. They measured their heart rate, blood pressure, respiration rate and blood flow in the brain.
The researchers expected to see an increase in heart rate and an increase in blood pressure, but these numbers remained virtually unchanged.
“We were very surprised. In the literature we read, it was said that the blood vessels would contract, and this would make the pulse quicken. The blood vessels did constrict, but we only saw a slight increase in heart rate because people were tense due to the discomfort associated with being in cold water.”
“It's amazing that we found no effect on blood pressure and heart rate. We also expected increased blood flow in the brain, but we saw the exact opposite,”says Bu Belhage.
Hyperventilation and slowing blood flow
The cold water bath presented several surprises.
“We saw that as soon as the volunteers' bottom went into the ice-cold water, their lungs, purely reflexively, began to hyperventilate the body,” says Boo Belhage.
Hyperventilation is what happens when, during breathing, air begins to be drawn in faster than normal, and more than seven liters of air per minute enter the lungs. During the minute of the experiment, the average for the volunteers was 35 liters of air per minute, but some of the participants inhaled 200 liters of air per minute.
At the same time, the blood flow in the volunteers' brains weakened. For some, it dropped to 25% of the normal, and on average dropped to 50%.
Never swim alone in winter
The shock effect comes in a minute and is dangerous.
During the experiment, two untrained winter bathers lost consciousness. And if you faint in the water, then you drown. Therefore, you cannot swim alone in winter. Walruses and science recommend starting winter swimming in summer.
“If you start in August, you will gradually get used to the thrill and become an expert walrus,” recommends Boo Belhage.
Yogis react to bathing in icy water just like beginners
But what happens during a workout? Is the process going on in the body, brain, or both?
To find out, the researchers compared the results of inexperienced walruses with those of two other groups:
- experienced walruses;
- experienced yogis.
The researchers did not see any real changes in the bodies of the experienced walruses. These people made a light "wow" when submerged in water, but could stay in it for up to five minutes at a time. Their heart rate did not increase, and neither did their blood pressure.
The yoga practitioners have never bathed in winter before, but they are known to have good control of their breathing. Nevertheless, there was practically no difference between their reactions and those of those who had never been a winter swimmer or practiced yoga.
“If it was purely psychological, then yogis had to resist it, but since the effect is to a certain extent reflex, they could not do it. Exercise can prevent a lot. Apparently, the body of experienced walruses is learning. Another study showed that the human body can then remember this experience for up to six months,”says Boo Belhage.
Is winter swimming healthy?
Studies show that walruses take fewer sick days and feel healthier, but scientists cannot say for sure which is the cause and which is the effect.
Do healthy people like to swim or does a person get healthier from winter swimming? Not much has been written about this.
“In a German study, the effect of winter bathing on the breakdown of sugar in the body was studied for six months. Scientists found that a person's need for insulin was cut in half. This says that winter bathing speeds up the metabolism of sugar in the body, which may lead to a decrease in the propensity for diabetes, but here you need to emphasize the word “maybe” in bold,”says Bu Belhage.
If you want the positive effects of winter swimming, Bu Belhage recommends swimming about three times a week.
Jens Urth