It looks like those warm lazy days of summer are coming to a close and our unusual 72 degree waters are beginning to gradually cool. Knowing that the ocean temperature is dropping into the 60's and before we know it will be in the chilly 50's come winter, here is some information that will hopefully help you avoid a case of hypothermia.
The first thing swimmers should be aware of is that cold water affects the vital organs much faster than cold air. Because water is an extremely efficient conductor, immersing your 98.6 degree body in a 60 degree ocean is a recipe for hypothermia. When your core body temperature drops even a few degrees your brain and vital organs become affected. If this happens, incontrollable shivering sets in, your speech begins to slur, and you start to lose your coordination and fine motor control. If your core body temperature drops into the low 90's, you'll become semiconscious. Any lower and your heart will be affected and begin to slow and eventually stop.
So how do you prevent hypothermia? Its best to start with your brain. A part of the brain called the hypothalamus is your body's temperature regulator, and it can be conditioned to differentiate between cold water swimming from other forms of exercise. The body usually responds to physical exertion by shunting the blood to the surface vessels just under the skin in order to dissipate the heat generated by exercise exactly what you don't want when you're swimming in the cold ocean. However your body can learn to recognize water and conserve body heat when you're in it. Within two weeks your body can adapt to the cold by taking daily dips in the ocean, gradually increasing the length of each swim but always staying within your comfort zone.
It also helps to have a little fat on your bones, or at least to dress fat (that is, to wear a wetsuit.) Body fat is a great insulator, and nature's way of protecting our vital organs from exposure to cold condi tions. Without body fat or a wetsuit, your body will have difficulty warming up and could quickly become hypothermic.
Fortunately swimming is a very good way to generate body heat, because it is a relatively inefficient form of exercise. When you exercise muscle, you have at best a 25% efficiency rate according to sci entific studies. The percentage efficiency rate (for example a 25% efficiency rate) means that when you burn 100 calories, you use 25 of them for mechanical (muscle) work and the rest are lost as fric tion. The friction is what generates heat. Swimming's percentage efficiency rate is closer to 7%, meaning you generate more heat. The harder you work while you are swimming, the more calories you will burn, thus you will maintain a higher body temperature and have a higher heart rate. If you cannot sustain a high rate, then you'll end up getting cold.
If you or one of your buddies does become hypothermic, the first thing to do is get out of the water. Once out, the victim needs to get dry and out of the wet swimsuit. Warm the body gradually by putting dry clothing on, or wrapping up in a warm blanket, and move to a warm place. Heat pads or other heat sources will help, but always keep a barrier between the heat source and the skin to pre vent a burn. If the victim is alert, give warm liquids to drink. Do not warm up a hypothermic victim too quickly, nor immerse the victim in warm or hot water. Rapid warming can cause dangerous heart problems.
In cases of severe hypothermia, the victim may be semi-conscious or unconscious. Begin treatment for severe hypothermia by caring for life-threatening problems. Call the local emergency number (9-1-1) or get the lifeguards. The victim of severe hypothermia might have slowed or stopped breathing, as well as a slow and irregular pulse. Keep checking their breathing and pulse. Give rescue breaths if necessary (one full, gradual breath every five seconds) and be prepared to start CPR. Continue to warm the victim until emergency medical personnel arrive.
Before you go out in the ocean for a long swim there is one more important thing you need to know:
your limitations, the best thing an open-water swimmer who's cold can do is get out of the water. If you don't get comfortably warm after a reasonable time swimming in the water, then get out, and try it again on a warmer day. Swim smart and swim safe.