Soon after a cold water swim, you may experience what’s called an “after drop”, or continued cooling.

Although previously thought to be a result of altered blood flow, the after drop is actually a conductive phenomenon. When rewarming after a cold swim, while the skin is exposed to warm air or water, the core is still losing heat to the cold muscles and fat of the surrounding tissues, and therefore has a delayed response to warming up.

The body’s natural response is to shiver to generate heat and gradually restore a deep body temperature of 36.5 – 37.5°C. Frequent exposure to the cold will result in a decreased metabolic response to cold (shivering) over time.

How long does the “after drop” last?

The length of time is takes for your deep body temperature to be restored to normal levels depends on various factors, such as the temperature of the water, the length of time that was spent in the water, and your adaptation to cold water.

The rewarming period may last from a few minutes up to an hour in extreme cases, such as after being exposed to ice water. During this time it is normal to experience shivering as your body heats itself up.

The best way to rewarm after a cold swim:

• Remove wet clothing as soon as possible and dress into dry, warm clothing. Also make sure you are sheltered from cold draughts.
• Cover areas prone to heat loss (head, neck, arm pits, groin). This can be done by wearing a beanie, scarf, and warm jacket, for example.
• To improve your comfort, it helps to warm the body from the inside out. Drink a luke-warm, energy-rich drink such as hot chocolate. This will also provide energy for reheating through shivering.
• In extreme cases, gradual external heat can also be provided, such as using heaters and luke-warm hot water bottles (be careful not to burn your skin).
• Avoid getting into a hot shower or going for a run soon after a cold swim, as this will promote blood flow away from the core, which is counterproductive to the rewarming process.

The swim itself is only a part of the challenge – the real challenge is the recovery. Be sensible and responsible when taking part in open water swims. Have a tough mind, but be smart enough to listen to your body and to stay safe during your open water swim.