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Effects of cold water
I am relatively new to open water swimming and I am loving it!

I joined this lovely group last year when I was a happy but very slow breast stroke swimmer and I have finally mastered how to do the front crawl and am now training for the Thames Marathon which is a bit daunting but a real challenge.

I was asked to write an article about the effects of cold on our bodies when we swim in cold water and let’s face it, it’s been really cold recently!  Many of my friends think that I am even more crazy than usual but I find it so exhilarating and I find that I look forward to immersing my body in freezing water each Saturday…

I have been nursing for many years, mainly in Intensive Care units both here and in Australia. During my time I have dealt with a fair amount of drownings and hypothermia; interestingly more drownings here than in Australia as they had stringent rules about enclosing swimming pools.

I would point out that I have never looked after an open water swimmer that has got into trouble so a lot of this information is for interest and not a premonition.

I have been reading around about the effects of cold water on us crazy winter swimmers and will share the following points:
  • cold water cools the body 25 times faster than cold air
  • swimming will increase the loss of heat from the body
  • muscle rigidity, loss of manual dexterity and physical weakness occur at a body temperature of 35 degrees
  • mental ability will also start to deteriorate at 35 degrees ; my temperature when I got home last week was 35 degrees but no one noticed a change, which is a worry.
There are 3 phases of cold shock:

Phase 1-first 4 minutes after immersion in cold water
  • Gasp response
  • Inability to hold breath
  • Respiratory rate increases
As a result of this CO2 levels will fall, reducing brain blood flow and O2 supply. Peripheral blood vessels constrict, heart rate and blood pressure rise, increasing the workload on the heart and can cause life threatening rhythms.

Phase 2- first 30 minutes leads to cooling of peripheral tissues, which has a poor effect on neuromuscular activity.  This can be significant in the hands leading to stiffness and loss of power; this can make it difficult to execute survival procedures
Most fatalities occur in these 2 earlier phases

Phase3-onset of hypothermia-classified as 35 degrees or less
Mild-32-35 degrees-shivering (thermoregulation) can persist
Moderate-28-32 degrees-thermoregulation diminishes, conscious level decreases
Severe-less than 28 degrees- Loss of consciousness, no shivering, life threatening heart rhythm-(VF)

So why take the risk?

As long as we don’t drown cold water swimming can -
  • Boost metabolism-by increasing circulation and activity focused on generating internal heat
  • Stimulate the parasympathetic  nervous  system-releasing neurotransmitters  such as serotonin which are a vital part of keeping us happy and free from depression
  • Increase production of testosterone and oestrogen, enhancing libido…..
  • Improve skin health and tone
  • Help activate the immune system
  • Be brilliant fun, a bit whacky and you make new friends
Other random facts about our hobby:
  • It has been suggested that women can retain their heat better than men-apparently we have a more even distribution of subcutaneous fat !
  • Women’s core temperature is 0.25 degrees higher than men’s-one effect of this is that our hands and feet get colder more quickly
  • As fat insulates, it can delay hypothermia and can improve physical stamina in the water
  • Repeated exposure to cold water can increase the layer of subcutaneous fat
  • You burn approximately 200 more calories per hour more in cold water
  • Cold water increases your white call count which helps fight infection
  • It helps to flush your circulation
FYI-in March 1984 Icelandic fishermen Fridthorrson was the only survivor of a boat that capsized in water of 5 degrees-he swam for 6 hours-It was thought that his survival was due to his high BMI (30); his physique was similar to a seal.

There are plenty of amazing people who swim for long periods in really cold water who repeatedly defy the odds-they have acclimatized themselves—read about Stig  Severinsen and his rather interesting swims!

I hope you find this interesting.  We have certainly acclimatised ourselves to the cold this year and I find that I can cope with cold weather so much better now.

Here’s to a fantastic year of swimming!!

AS YOU'RE HERE: The HOWSC website is maintained and run by HOWSC members and relies on voluntary contribtutions.  Do you have something you'd like to share?  Maybe reflections on a recent swim, tales of adventures in far flung places, an account of your watery accomplishments? Photographs, videos, poetry, prose, art and more will all be gratefully received and published on the website for all to admire.  Contact Mark Reed to discuss or submit your contribution.  We look forward to hearing from you.
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