How and Why

Designers sweat the details to let athletic clothes breathe

By Leslie Tamura
Tuesday, August 10, 2010

Most of us are familiar with dry-wick athletic apparel. We see the advertisements claiming that this shirt has the textile technology to keep you dry, that those shorts can wick away your sweat, that this fabric will keep you feeling cool and comfortable during the most intense workouts.

But what's the science behind these promises? How do dry-wick textiles actually work?

It comes down to two principles: percolation and evaporation. "Moisture-management" fabrics absorb the sweat from your body, propelling it away from your skin, then spread it throughout the garment so it can easily vaporize into the environment.

But these products differ in how they use various fibers. A natural fiber may absorb more than a synthetic fiber, but a synthetic fiber may dry faster. Searching for the desired balance between wicking and drying, manufacturers mix different amounts of natural and synthetic fibers or transform an individual fiber's silhouette. The fiber recipe determines how the overall garment copes with sweat.

Natural fibers tend to love water. They pick it up whenever they can. Synthetic fibers, however, do their best to avoid or repel water.

Cotton is a natural fiber and a fantastic lover of water. When you sweat, cotton fibers will absorb the fluid, "wicking" the droplets away from your body. But because cotton fibers love liquid so much, they don't give it up very easily. The cotton fabric will hold onto the water, absorbing moisture into its fibers, resisting evaporation.

This is why it takes so long for your cotton T-shirts to dry.

"With natural fibers, you get what Mother Nature makes, and you have to live with it," said Becky Rose, an activewear research and development fellow for Invista, the manufacturer of Coolmax fabric. "Sometimes it's good, sometimes it's not so good."

Wearing a cotton shirt during a workout may feel cool because you're essentially wearing a shirt drenched in your bodily fluids, but as your core body temperature comes down, you may experience post-workout chills. Your cotton shirt does not want to dry, and you're left feeling cold and clammy.

"For athletic wear," said Yiqi Yang, a professor of textile chemistry at the University of Nebraska at Lincoln, "you want [the fabric] to wick water as good as cotton, but you don't want it soaked."

At the other end of the spectrum is polyester.

Polyester wants nothing to do with water. Its synthetic fibers are not tempted to absorb the beads of sweat pooling along your skin. When you do sweat, a 100-percent polyester shirt will simply trap the beads of sweat against your skin, often forcing the liquid to just trickle down your body. Polyester may just leave you feeling wet.

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