No Sweat: The Truth About Performance Apparel

Performance-apparel companies have introduced garments that are made with cotton, synthetic and wool fabrics that they claim will improve your performance when you exercise. But no independent data back up these claims, and the results of our lab tests indicate that these shirts keep you about as cool as wearing no shirt at all.

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If you have walked into a sporting-goods store in the past 3 years, you probably noticed that buying a shirt isn’t as simple as just picking up a cotton T-shirt in a color that you like.

These days, the shopping aisles are full of a variety of performance apparel—shirts, pants, jackets, socks and tights that are touted as being capable of  regulating your body temperature, keeping you comfortable and improving your physical performance.

Performance apparel rang up about $1.3 billion in sales in the United States last year. At least 60 companies now make these garments, which can cost roughly $10–$50 for a short-sleeve shirt and up to $300 for a pair of pants.

Performance-apparel commercials and print advertisements typically use college or professional athletes as endorsers. And the gear is marketed toward anyone who might work up a sweat—even toddlers.

“The lines between traditional ‘sports/performance apparel’ and normal everyday clothes are increasingly blurring,” says Janet Shim, who is a retail analyst for IbisWorld, which is a market-research group. “More consumers are wearing performance apparel to run errands and do everyday chores.”

If you’re wearing these clothes to run errands —or around the block—they aren’t improving your “performance.” We spoke with 14 exercise experts, physicians and scientists, and none of them nor the apparel-makers themselves knew of any independent, peer-reviewed evidence that performance apparel of any kind has any measurable influence on regulating temperature and improving performance. But all of our experts agreed that performance apparel will have no effect on regulating body temperature unless you’re pushing your body beyond its limitations.

“If you’re in an extreme environment, where you are challenging yourself beyond your physiological capability, then maybe one of these things can make a difference,” says Delia Roberts, who is a fellow at American College of Sports Medicine.

“But for a recreational runner, I don’t think it makes a difference.”

Through the Paces: Testing Three Fabrics

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We evaluated T-shirts that were made of three different performance fabrics that promised to wick  away moisture from the skin and keep exercisers cool and comfortable. Our results suggest that the fabrics might indeed keep sweat from accumulating on the skin, but this didn’t keep runners cooler or more comfortable than when they wore no shirt at all. (See "Through the Paces: Testing Three Fabrics.")

“These fabrics are probably more of a fashion statement than something functional,” says William Sands, who is the former head of Sport Biomechanics and Engineering for the U.S. Olympic Committee. (Sands also is director of Monfort Family Human Performance Laboratory at Colorado Mesa University, which conducted our evaluation.)

In other words, these shirts might make you feel more comfortable and look trendier at the gym, but we remain unconvinced that they’ll help you to breathe more easily, run longer or lift more weight.

WICKING OR STICKING? Most performance apparel is designed to wick (or pull) away moisture from the skin and through the clothing surface, so the moisture evaporates to leave you dry while you exercise.

Moisture-wicking claims are legitimate and typically are achieved by using one of two methods, says George Havenith, who has studied these fabrics at Environmental Ergonomics Research Centre, which he directs at Loughborough University in England.

The first way to promote moisture wicking is to apply a hydrophilic surface treatment, such as silica, to a fabric. This treatment allows the fabric’s fibers to attract water and pull it into the fabric and away from the skin, Havenith says. The second way is to use a knit structure that involves two types of fibers. The fiber that touches the skin absorbs little moisture, but it wicks away the moisture to the fiber that’s on the outside of the fabric, which is more absorbent, Havenith says.

This process leaves your skin feeling drier. But it won’t make your body temperature any cooler or extend your endurance, says Nigel Taylor, who directs thermal physiology research at University of Wollongong in Australia. Sweat cools you when it evaporates from your skin’s surface, and (depending on the individual) you might cool down less if the evaporation happens on the outside of the fabric instead of on your skin, Taylor says. Consequently, a shirt could cool you less than bare skin does.

“It’s always better to have the sweat evaporate on your skin than on a garment that’s flapping in the wind away from you,” says Timothy Gavin, who is an exercise physiologist at East Carolina University in Greenville, N.C. Gavin published studies in the journals Sports Medicine and Medicine & Science in Sports & Exercise that reported on how different types of clothing influence the body’s capability to keep cool in the heat. None of his research found any discernible effect regardless of fabric types.

That doesn’t surprise Thomas Altena, who is an associate professor of health at Missouri State University and is a triathlete. He believes that the benefits of performance apparel are all in the mind.

If you do 30–60 minutes of weight training or playing a game of pickup basketball, performance apparel isn’t going to make your performance any better, he says. “There might be a psychological effect of having something new, feeling good about yourself.” Call it retail therapy, Altena says.

No fabric helps the body to regulate temperature better than bare skin does, but if you have to wear clothing (and most of us do), fabrics that wick away sweat will make you feel drier and more comfortable than will fabrics that absorb water, Taylor says.

BACK TO NATURE. Polyester and polypropylene ruled the performance-apparel market up until 2 years ago, but lately we’ve seen a surge of “natural” fabrics that are made from cotton and wool. The performance-apparel industry has been criticized for its use of resources that aren’t renewable or biodegradable, Shim says, and manufacturers responded by developing products that use fibers such as cotton and wool.

At least 20 manufacturers claim that their newest garments that are made with new fabrics can surpass synthetics in terms of comfort and performance. (And what a surprise: They charge $25–$30 for one of these T-shirts!) That’s an about-face from 3 years ago. Performance-apparel manufacturer Under Armour went so far as to proclaim that “cotton is the enemy.”

In reality, cotton is no enemy, Havenith says. Natural cotton has a tendency to hold moisture and keep it close to your skin, and that can be a good thing in the heat.

“When you stop [exercising], it feels like a cold towel against your skin. We call that ‘after-chill,’” Havenith says. After-chill can be dangerous if you work out in cool conditions, but it can be refreshing on a hot, sunny day, he says. But cotton can become heavy and uncomfortable as it absorbs sweat after a prolonged period.

To match the wicking capability of synthetic fabrics, the cotton-industry group Cotton Inc. patented a technology that’s called TransDry and introduced it in 2008.

Performance-apparel-maker Longworth became the first to adopt TransDry in its products when it introduced the material into its Polarmax brand of garments. TransDry garments consist of several different cotton yarns that are treated with a proprietary chemical to alter the absorbency. The result is fabric that’s made to wick and spread moisture away from the skin, says David Earley of Cotton Inc. He claims that TransDry dries just as fast as typical performance polyester fabric does.

Under Armour took notice and last year began to market its own line of TransDry apparel under the name Charged Cotton.

“We were never against cotton,” says David Ayers of Under Armour. “We were just against products that don’t perform for athletes.”
Our investigation found that Under Armour’s performance claim holds up: Charged Cotton has the same cooling effect on body temperature as at least one synthetic fabric does—in other words, no effect at all. We called Under Armour back for its response to our study, but the company didn’t return our calls by press time.

Wool is another natural fabric that’s making inroads into performance apparel. At least six companies now sell premium ($35 and higher for a T-shirt) performance apparel that’s made from merino wool, which is a special variety of New Zealand wool that’s prized for its fine, soft texture.

Unlike other fabrics, wool fibers are porous and absorb sweat vapor instead of just sweat droplets, Taylor says. Wool long has been known to provide good performance in cold conditions, because it insulates you (and thus keeps you warm) even when it’s wet.

The treated merino wool that’s used by performance-apparel companies is made of fine fibers that don’t prick the skin as fibers of conventional wool do. Lightweight wool such as merino wool performs best in hot, arid environments, where it helps to speed the evaporation of sweat, says David Harms of Smartwool, which makes merino-wool performance apparel.

But do any of the claims about merino wool hold up? We didn’t find any independent studies beyond ours that showed that. Amy Klee, who is a designer for Icebreaker, says our study proves that merino wool performs as well as do cotton and synthetics in heat. But she didn’t comment on why no performance fabric (wool or otherwise) performed better than bare skin does.

EVEN MORE CLAIMS. Performance-apparel-makers’ claims go beyond moisture control and temperature regulation. Companies tout wool’s natural ability to inhibit the microbial growth that leads to body odor. At least one study, by researchers at University of Otago in New Zealand, confirmed that wool retains fewer odors than do synthetics that contain polyester, which are notorious for breeding bad smells.

But wool’s advantage here might not be as great as it once was. For the past 2 years, AYG, Columbia, Patagonia and Under Armour have treated most of their synthetics at all prices with minerals and salts to make them odor-resistant. We found no independent studies to prove that the treatments work, but Havenith says it’s reasonable to expect silver to reduce odors, because it’s been shown to reduce the growth of bacteria that create odors in clothing.

Less plausible, however, are the claims that manufacturers make about a new treatment of fabric—the use of infrared light to result in a boost of energy, an increase in oxygen levels and a reduction of pain. Hologenix and Schoeller produce this fabric, and several brands of apparel—notably Reebok—have adopted the fabric. A pair of tights that’s made from this exotic material starts at $100. But Dr. Harriet Hall, who is a retired physician who specializes in investigating medical claims and an editor of the website Science-Based Medicine, calls these infrared-light claims “preposterous.”

East Carolina University’s Gavin scoffs at the claims of benefits from infrared light in clothing. “It’s true that we radiate heat through infrared radiation, but usually when you’re exercising, your biggest problem is losing this heat, not keeping it in,” Gavin says.

Hall also rejects the claims of kinetic-energy-absorbing fabric. Seth Casden of Hologenix says the company’s textiles contain a mineral-embedded polyester that’s called Celliant, which absorbs the wearer’s kinetic energy like a sponge and returns the energy to the wearer. Casden claims that his company’s tests have shown that the technology reduces pain, increases blood flow and blood oxygen levels, and helps to balance body temperature. But no independent tests have been conducted to verify this claim, and Hall says none of these claims has any clinical or even preclinical evidence to back it up.

Tom Weinbender, who is president of Schoeller USA, says wearing a garment that’s made of his company’s energear fabric allows your energy to last longer. But he was unable to explain the specifics of how it works.

“It’s an old science that’s been in Asia for hundreds of years,” he says, and he compared it with the (unproven) benefits of wearing a copper bracelet to improve arthritis symptoms.

Our research suggests that instead of selecting apparel that’s based on technological claims, you’re better off to base your choices on comfort and price.
“A lot of it just comes down to personal preference,” Gavin says. “If you like the feel of one type over another and that makes you exercise more, then that’s a good thing.”

Just don’t expect your performance to improve as a result.

Christie Aschwanden is a contributing editor for Runner’s World and Bicycling. A former competitive athlete, she’s also written for Science, Slate and The New York Times.

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