Manage The Dive Response
When cold water touches the thermal receptors around your nose and eyes, it causes a reflex known as “cold shock” or the “dive response.” The colder the water, the greater the response. You gasp. Your heart rate slows by about 25 percent and blood vessels constrict in the extremities to keep oxygenated blood in your vital organs. Trying to swim in this state places enormous stress on your cardiovascular system, and you will feel very anxious. Don’t start to swim until you have worked through the initial shock. Always splash your face and neck before you put your whole face in. Stay inside your circle.
By planning ahead, you can also better prepare your body for cold shock by taking these steps: Submerge to the neck in water that’s 60 degrees or colder. Don’t wear a wetsuit. Stay in the water for three minutes (a cold shower does not work).
On race day, get in the water and swim for at least 10 minutes to warm up before your wave goes off. Swim long enough to get into your circle and find your swimming groove.