It seems that Cold Exposure has become quite popular recently. But, is this practice harmless?
The history of Cold Exposure
Hippocrates, the Father of Medicine, said that water therapy relieved the apathy and lethargy. However, we would have to wait until this therapy would actually become a trend.
In 1750, medicine books started to advise swimming in the sea in order to treat many different diseases. According to these documents, winter was the best time of the year to do so.
Wim Hof Method
One of them is the Wim Hof method, which combines breathing exercises and cold exposure. It has become extremely popular and he claims that it can improve the immune system, pathologies such as depression, or simply sharpen the focus.
Anything that involves “personal growth” or “improving our physical and mental health” is quite catchy and it quickly becomes a trend.
But today, we are going to analyze the dangers of uncontrolled cold exposure from a scientific point of view in order to be more aware of what we are dealing with.
Disclaimer: we are not trying to send hate to anyone here…
Dangers of Cold Exposure according to Science
According to the WHO, 372 000 people (42 per hour) died from drowning only in 2012, being the third cause of non-natural death.
In order to know why can someone die due to cold exposure, we need to understand a few basic concepts:
- Cold water: <15 degrees centigrade (Mike Tipton, who investigates the human physiological response to extreme environments).
- However, the thermoneutral zone for some who does swimming is 25 degrees centigrade.
- The lower the temperature, the less time it will take before we enter hypothermia and vice versa.
What happens to the body when the body temperature drops?
- We start shivering at 36ºC. This is a body reflex in order to increase the body temperature by triggering involuntary physical movement.
- Around 35ºC, we will be confused, disoriented and we will no longer look for help. You feel apathetic, nothing matters and you start fading.
- Amnesia strikes at 34ºC, you start losing control of what happened and you have a hard time remembering things.
- At 33ºC, it is much more probably to experience heart arrhythmia.
- If you reach 30ºC, you will probably faint and lose consciousness. If you can grab onto something you will not drown, but things get grim if you are swimming in the middle of nowhere.
- Ventricular fibrillation is almost guaranteed at 28ºC, which is the most frequent and lethal type of arrhythmia.
- Finally, we reach the temperature that establishes the limit that is compatible with life, 25ºC.
However, there are always outliers…
The risks of cold
Years later, science has discovered other potential risks of cold exposure that have little to do with hypothermia:
Cold shock response
There are thermoreceptors in our skin that start to function when we dive into cold water. In general, they trigger hyperventilation, which sometimes can be consciously suppressed.
If this hyperventilation lasts for a long time, it causes the so called “respiratory alkalosis”. This increases the blood pH to a more basic pH.
This happens due to an interesting phenomenon, a conflict of the autonomous nervous system due to the concomitant activation of two of its main components:
- The sympathetic nervous system, which is activated by the thermoreceptors we just mentioned.
- The parasympathetic nervous system, which is activated by the immersion response, specially due to diving into the water or apnea.
This activation of opposite systems makes it much likely to experience heart dysrhythmia and arrhythmia.
Specially if there is a prolonged apnea or predisposing factors such as long QT syndrome, heart ischemic diseases or ventricular hypertrophy.
Diving into ice-cold water
Nerve paralysis and neuromuscular incapacitation
The nerve function slows down with temperatures under 20 degrees centigrade.
When we do a cold exposure between 5-15 degrees for several minutes, we may experience a symptomatology that equals peripheral nervous paralysis. This can result in drowning due to the inability to stay afloat.
Less physiological adaptations to physical exercises, specially strength and hypertrophy
Yes, that is right…
It seems that the typical ice-cold water immersion or ice baths that athletes use to recover from an important physical effort are actually a double-edge sword:
- On the one hand, it seems to relieve the muscle pain and buffer the inflammation
- On the other hand, it interferes with the molecular adaptations to physical exercise, specially with the anabolic signalling that leads to muscle hypertrophy.
That is all for now, see you in the next post! Cheers!
- Stocks JM, Taylor NAS, Tipton MJ, Greenleaf JE. Human Physiological Responses to Cold Exposure. Aviation Space and Environmental Medicine. 2004.
- Tipton MJ, Collier N, Massey H, Corbett J, Harper M. Cold water immersion: kill or cure? Exp Physiol. 2017;
- Cochrane DJ. Alternating hot and cold water immersion for athlete recovery: A review. Physical Therapy in Sport. 2004.
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