STRATEGY COLD WATER ACCLIMATISATION THERAPY SHOCK Cold-water shock and hypothermia are killers. Avoid them. Mat hew Jones fi nds out how…
Last issue we looked at some of the benefi ts of cold water swimming and how to acclimatise (Cold Comfort, Dec 2011/
Jan 2012). This issue we examine the dangers – primarily cold-water shock and hypothermia. Cold water immersion has been studied extensively by scientists investigating how cold water claims lives, and how this can be prevented. One of the biggest hazards for the unwary is cold-water shock. The cold-water shock response is characterized by a sharp gasp and a rapid rise in heart rate, triggered by the release of stress hormones such as adrenaline. This is followed by constriction of blood vessels near the surface of the body. Scientists have found that the ability of a swimmer to hold his or her breath is reduced by this involuntary refl ex, and the drive to breathe appears to be increased. Even more concerning is the reduction in blood fl ow to the brain that coincides.
Fortunately, the shock response can be managed and reduced. For example, entering cold water in two 30-second stages has been found to reduce the sharp increase in breathing rates by up to 35%, while another study found the breath-holding ability of subjects immersed in 12 °C water could be increased using mental preparation techniques, such as goal set ing and positive self-talk.
In the study, an acclimatized and psychologically prepped group showed a 120% increase in maximum breath-hold while immersed, compared to a 73% increase in the group who were just habituated and not psychologically trained. Cold water shock can disable and kill a swimmer within minutes but its impact is immediate, obvious and can be mitigated. Hypothermia – a disabling drop in core body temperature – can also kill, but its onset is more insidious.
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