Cold Incapacitation

OSS Breaststrokes Windemere

The main safety risks you face as a wild swimmer are from getting too cold. You get in, and after a couple of minutes of feeling uncomfortable the water feels pleasant. As a novice swimmer, or even as a strong swimmer with limited experience of swimming outdoors, you then attempt to cross the lake, but half way across start feeling cold again.

Your body continues to lose heat, blood shunts to the core to keep organs warm. Your muscles lose power, limbs become slow and heavy, and swimming becomes increasingly difficult. This is cold incapacitation and it can all-too-easily lead to drowning.

A further effect of cold incapacitation is the loss of coordination we all suffer as we become cold. The bank that previously seemed a safe exit point might now be difficult or even impossible for you to climb as you struggle to grip with your hands, while your limbs are clumsy and numb.

The media often report water related deaths as if they are mysterious, as if we can’t predict what will happen when we’re in water, and therefore we should just stay out. This isn’t true. We know how cold impairs swimming, and we can moderate our risk by:

  • Wearing a wetsuit, silicone hat, maybe even booties and gloves depending on the time of year (see our wetsuit Q&A)
  • Swimming close to the shore
  • Acclimatising
  • Knowing our limits outdoors in terms of water temperature, conditions, fitness and swimming ability.

In truth, there are very few swimming deaths (in 2013 in the UK there were 59 out of a total of 389 water-related deaths).  Many factors can contribute to these deaths, for example alcohol or drugs can lead to impaired judgement and coordination and affect your body’s ability to regulate temperature. 126 people in the UK in 2013 apparently fell in to water and drowned while walking or running. These events are all tragic, but do not necessarily have lessons for the open water swimmer, who wants to reduce their own risks.

Rob Fryer from the River and Lakes Swimming Association referred us to research carried out by Portsmouth University and the Swedish National Defence Research Establishment, published in the Lancet in 1999, confirms that drownings associated with cold water are usually caused by cold incapacitation.

Golden and Tipton (Essentials of Sea Survival, 2002) also discuss the recurrent misunderstanding of the causes of drowning; while drowning is usually the cause of death after immersion in cold water, it’s the cold shock response that kills some individuals first, and cold incapacitation following from that which kills many more. Both result in swimming failure and drowning.  Hypothermia, defined as a significant drop in core temperature, is as they say, not possible in humans in under 30 minutes of immersion because of the body’s protective mechanisms.