02/12/2011 by Carl Reynolds
I’m not swimming today, so thought I’d share what I’ve been gleaning from sources various about cold water acclimatisation. In a nutshell then –
1. as your skin gets cold it forms an insulative layer to protect your core. And reduces heat loss, as heat moves more quickly between different temperatures. In other words, the closer your skin temperature to the water temperature, the less heat you lose from your core.
2. the core stays warmer than the outside…for some time. According to what I’ve read a rectal thermometer will confirm this, but I have not experimented.
3. fat helps to insulate.
4. brown fat may or may not expand from its vestigial remains and generate some heat.
5. you lose heat from the outside of your body slightly differently. Extremities, like fingers, have less fat and lose heat quicker. Putting hats on reduces heat loss through your head, but does not account for the major part of your heat retention – despite the mythology that most heat is lost through the head. See here for a taster.
5. swimming regularly in cold water changes your ability to generate heat and maintain heat. In scientific terms you adapt your thermogenesis response.
6. you improve your body’s ability to only need to shiver at a lower temperature.
7. in freezing water you’ll stay alive for up to 30 minutes, but will probably drown before ten minutes is up, as you lose control of your limbs.
8. women seem to get out of cold water sooner than men…because they are smarter (generally).
For the science I looked at various on-line journals including International Journal of Sports Medicine (1987 Oct8(5):325-6), European Journal of Physiology, Experimental Physiology (2000, 85.3:321-326), Dr Jolie Bookspan (scuba-doc.com/coldjolie.htm), The Lancet (1999, Vol354, Issue9191, p1733) and an excellent series of articles about cold water acclimatisation and habituation on Lone Swimmer. Which also references other scientific sources.
A comment on an earlier post also suggested that you extract more water from your blood, hence the oft observed need for cold water swimmers to pee more. But I’ve yet to find the science on this.
*disclaimer…I am not a scientist, so am open to correction, as I may have misinterpreted what I have read.