Your Fancy Non-Cotton Workout Clothes Stink

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Photo: Alex Macro/Corbis

Cotton is rotten” goes the exercise apparel mantra favored by runners and outdoor enthusiasts. But some new research suggests we’ve got it backwards, at least when it comes to smelliness: Synthetic workout gear smells worse than cotton clothing one day after a sweaty exercise session, according to a new paper published in Applied and Environmental Microbiology.

After participating in a sweaty, hour-long spin session, 26 study volunteers handed their T-shirts over to a team of Belgian researchers, who kept the shirts incubated for 28 hours. When they checked in with the clothes, a “trained odor panel” deemed the polyester gear smellier than the cotton, according to the press release, which offers this by way of explanation:

Freshly secreted sweat has little odor, because the long-chain fatty acids the axillaries secrete are too big to be volatile, says first author, Chris Callewaert of Ghent University, Belgium. Bacteria break these, as well as hormones and sulfur compounds, down to waftable sized, odoriferous molecules.

On the clothes, the main culprit bacteria are micrococci, says Callewaert. “They are known for their enzymatic potential to transform long-chain fatty acids, hormones, and amino acids into smaller—volatile—compounds, which have a typical malodor.”

Staphylococci, which inhabit both axillary skin and adjacent textiles (the latter with much less diversity), create a normal, non-malodorous body odor, he says.

And micrococci — again, this is the bacteria responsible for the smell — seems to grow better on polyester clothing than cotton, Callewaert explained in the press release, although it’s not entirely clear why. So the solutions, if you’d rather your laundry basket didn’t smell like a locker room, are as follows: Wear cotton clothing when working out, which Callewaert says will minimize the stink. Or, if you don’t want to wear cotton, Scott Douglas over at Runner’s World points out that workout gear made from merino wool is also odor-resistant. Or maybe just wash your sweaty clothes before the bacteria have time to “incubate” (shudder).