COTTON AND HYPOTHERMIA

The ubiquitous cotton T-shirt. Comfotable when clean, rather less so when dirty, and very slow to dry even in warm weather. In fact, the cotton T-shirt is so slow to dry that the biker usually does not bother washing it. And with the passing of days and weeks, as the shirt grows ever more soiled and odiferous, it begins acting as a people repellant and attractant for other living species.

On a cold day, when cotton becomes wet -from sweat for example- it can sap vital body heat. Cotton fibers are hydrophilic, meaning that they absorb moisture. This is why the biker who wears cotton, and who sweat-soaks those garments in cold weather, will be socializing with hypothermia at every rest stop. Even as little as one percent cotton in a garment is unfavorable.

Certain synthetics (like polyester and polypropylene) are hydrophobic, meaning that the individual fibers do not absorb moisture appreciably. (Nylon is fractionally absortive, making it somewhat slower drying than the true hydrophobics. This is why the cycling jerseys must be polyester and polypropylene or Thermax, rather than nylon). Any synthetic garment is as cold as a cotton one when wet. However, the synthetics are faster drying; so in essence they are much more forgiving, which helps explain their popularity in today's outdoor apparel.

People sometimes experience reactions to synthetic fabrics. Generally, the fibers themselves are inert, but some of the chemicals added to them can cause sensitivities. Which is not to infer that cotton garments are chemical-free either, by any means. But for most people, synthetic cycling garments offer the best performance, comfort and safety.