Afterdrop is the term used to describe the condition where your body temperature carries on dropping even after you have removed from the cold environment. It is a term often used by open water swimmers, although it can happen to anyone who has experienced cold exposure.
Why does afterdrop occur?
Afterdrop can occur because your outer layer of skin becomes much colder than usual when you are in cold water and it continues to cool even when you are on dry land. During your swim, the body automatically directs warm blood to the core, to help you maintain a survival body temperature.
During this process, circulation is reduced to your outer layers of skin, and when you get out of the water, the colder surface layer of skin continues to lower your body temperature. At the same time, heat continues to flow out of the body. When we are engaged in the vigorous activity of swimming, this helps to generate internal body heat.
However, when we exit the water and rest, the heat production slows down, and we get colder. In the worst case scenario, this can result in hypothermia, although many people will just continue to shiver and feel chilly for up to 30 or 40 minutes after they have exited the water.
What are the risk factors for afterdrop?
The water temperature and the length of time you are in the water are the biggest factors that affect how low your core body temperature will drop after your swim. Obviously, the colder the water and the longer your swim, the greater the risk of afterdrop.
How prone you are to afterdrop is also influenced by how acclimatised you are to the conditions. Over time after repeated cold water exposure, it is possible that you become physically and psychologically adapted to the conditions, and therefore become less vulnerable to afterdrop.
Body Mass Index, fat distribution, and body shape can also be factors that affect a swimmer’s risk of developing afterdrop.
How can you avoid afterdrop?
To reduce the risk of developing afterdrop, it is important to remove all wet clothing and dry yourself as soon as possible after getting out of the water. Dress yourself in thermal layers, starting with the upper body. Also protect your extremities with gloves, thermal socks, and a hat.
If possible, avoid standing on cold ground as you change, but take a mat to stand on to avoid further heat loss through your feet. It is advisable to sit somewhere warm if possible, and sip a hot drink.
A warm bath or shower may help, but it is best to wait until you have warmed up for a while first, because sudden exposure to warm water can cause a change in blood pressure and lead to fainting.
Do not attempt to drive soon after getting out of the water, because afterdrop may not kick in immediately, and you may begin to shiver violently, feel dizzy, or even faint.
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