Don't Wear Cotton to Exercise in

Recently a good friend competed in a half marathon, her third, which she chose to walk. The day dawned bright, sunny and a little cool. The forecast said possible showers later in the day with a high temperature of 20 C. At this temperature most would choose shorts and a short sleeve shirt to run in, though my friend decided on long pants, a t-shirt and a light jacket because she would be walking. Her only, and near fatal mistake was that all three pieces were made of cotton.
   Cotton, although soft and natural, is a great sponge for moisture, think cotton balls. So when exercising in cotton all moisture is absorbed and stays next to your skin. When you slow down or stop, like at water stops, to stretch or at the completion of exercise, air flow over your wet clothing will cool your body down. This is exactly what my friend experienced. After walking 21k, her body temperature had dropped; she had impaired blood flow to her extremities, was very sleepy and couldn't form coherent words. After spending an hour in the medic tent being warmed with blankets, Mylar wraps and warm fluids (after removal of wet clothing) her body temperature began to climb. After multiple warm baths it took 2 days for her to not feel cold.
   When exercising vigorously indoors or out, summer or winter, wear synthetic fibers that draw moisture to the top of the fabric and away from skin where it evaporates, allowing you to regulate body temperature easier. Materials to look for when choosing your clothing should be Tectel, Cool-max, Dri-Fit, micro meshes, fleece and breathable outer layers that provide wind and water protection.
   No one imagines getting hypothermic at 17 C, so start out by dressing in synthetics with layers and be prepared to change your clothing as soon as possible after exercise.