Open water swimming is undoubtedly an adventure. When doing so in lower than usual temperatures, the experience can become even more intense. Before you take the plunge into waters at temperatures of 15 °C or below, you should first consider several important factors. To find out more on the subject, we spoke with Dr. Heather Massey an expert on thermal, altitude and survival physiology at the British University of Portsmouth. Massey not only tells us how best to acclimatize ourselves, but also explains how the body reacts to a dive into cold water.
When you immerse yourself in cold water, your body experiences a cold shock response. This is characterized by a sudden gasp, followed by rapid breathing and increased heart rate and blood pressure. This reaction happens when you get into water at about 10 °C or 15 °C, but it can also occur at higher temperatures, between 20 °C and 25 °C, although not to such extremes. The body's involuntary response can become especially problematic if your airways are underwater when you need to breathe, or if you suffer from an underlying heart or vascular condition.
This shock is produced by the stimulation of cold thermoreceptors on the skin's surface and it is especially likely to happen if the body is not acclimatized. In such cases, swimmers will experience a chilling sensation on their skin; however, if the water temperature is below 8 °C, pain receptors will also be stimulated.
EVERYONE EXPERIENCES COLD WATER SHOCK
Although it is true that before their first immersion in cold water, everyone will experience the same cold shock sensation, those who are acclimatized will no longer have such a pronounced or intense response.
Cold thermoreceptors are located approximately 0.18 mm under the skins's surface and above any subcutaneous layer of fat, so the body's response to cold shock is not affected by the amount of body fat an individual has. However, an individual's shape and size do influence the cooling of peripheral and deep tissues. That is, a lean person will get cold more quickly than a person with larger reserves of subcutaneous fat.
WEARING A WETSUIT DOES NOT PREVENT COLD SHOCK, BUT IT REDUCES THE AMOUNT OF HEAT LOST
Wearing a wetsuit will not prevent a cold shock response, because in order for the wetsuit to do its job, water fills the space between the skin and the suit. This layer of water will be cold at first and therefore stimulate the cold thermoreceptors and cause the body's response. Because wetsuits trap this inner layer of water slowly, the severity of the body's cold shock response may decrease with a more gradual exposure to cold water. This is why many people fill their wetsuit with water before they completely submerge themselves, so that they can overcome the cold shock response before they start swimming.
Although a wetsuit will not prevent you from experiencing an initial cold sensation, wearing a wetsuit will reduce the amount of heat your body loses, increasing your thermal comfort level and extending the time you can swim in cold water. They also bring their own performance advantages, such as improving buoyancy and swimming speed.
HOW TO ACCLIMATIZE
Short, repeated dives in cold water will gradually minimize your body's cold shock response. As few as 6 dives can reduce the change in breathing brought on by cold shock by 50%. It is recommended that swimmers enter cold water gradually, as diving in quickly will cause all cold receptors to be stimulated at once and intensify the cold shock response. Entering the water slowly, on the other hand, will diminish the reaction and allow you to acclimatize little by little.
Swimming in cold water requires profound self-knowledge as well as knowledge of your surrounding environment. These, along with Dr. Heather Massey's advice, will be very useful for any swimmer who wants to experience the sensation of swimming in cold water without sacrificing safety and comfort.