Afterdrop

Think of it like being in a fridge: when you swim, your body shuts down circulation to your skin, focusing warm blood on your core. With reduced circulation to your peripheries, skin, subcutaneous fat and muscle tissue start to act like a natural wetsuit.

When you’re back on land, this cold layer continues to cool your core, even if you’re back in warm clothes or a cafe. This is why you are likely to feel colder 10 minutes after you get out from a winter swim than you do the moment you exit. The length of the delay between exiting the water and your core starting to warm up depends on a range of factors, such as the water temperature and the length of your swim. Afterdrop can be really unpleasant, with shivering, faintness, nausea and, of course, the risk of hypothermia.

How to warm up

• Remove any wet layers and dry yourself as soon as possible.
• Get dressed! Don’t dilly-dally on the shore, riverbank or the edge of your lido.
• Layer up with thermals, jumpers, insulated jackets, hat and gloves, etc. Silver foil blankets don’t help swimmers. Unlike runners, for example, swimmers are not radiating heat after a swim, so there’s no escaping heat for the blanket to trap.
• Stand on something as you get changed to avoid losing heat through your feet. Some winter swimmers take a thermos of warm water which they pour into a small tub to stand in while getting dressed.
• Sip a warm drink. The scientists say the small volume of a hot drink has absolutely no effect on your core temperature, but even if the effect is psychological, it seems to work for us.
• Find a warm environment. Cars, with heaters on full, are popular with Channel swimmers. It is not recommended anyone drive themselves if cold – it is likely to impair function. Shivering is a sign you are not ready to drive.
• Move around to generate body heat.
• Saunas are great for cold people. Warm baths or showers are down to individual preference: some feel worse after going into them, some better. Just remember you may not be able to sense the water temperature so don’t make it too hot.

If you’re dealing with a cold person, rather than being the cold person yourself, follow the same steps from the start, making sure they remove all their wet clothes.