Why You Should Wash Those Dirty Gym Clothes Immediately

09/08/2014 08:26 am ET | Updated Sep 08, 2014
Robert Pavsic via Getty Images

Those fancy, sweat-wicking polyester workout clothes may keep you cool and dry while you exercise, but they might also stink a lot worse after sitting in your laundry basket awhile -- at least, compared with a cotton T-shirt, a new study suggests.

That's because odor-causing bacteria, called micrococci, seem to grow better on polyester than they do on cotton, according to the research, published in the journal Applied and Environmental Microbiology.

Even though freshly secreted sweat doesn't, on its own, stink, micrococci can turn sweat secretions smelly. The bacteria "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," study researcher Chris Callewaert, of Ghent University, explained in a statement. He noted that he is now investigating what it is about polyester that seems to better encourage the growth of this kind of bacteria.

For the study, Callewaert and his fellow researchers had 26 healthy people, with no skin infections or medical disorders, participate for an hour in an intense cycling session. Then, researchers took the shirts the participants were wearing while exercising and put them in separately sealed plastic bags, where they were kept for 28 hours at room temperature in the dark. The materials of the participants' T-shirts ranged from cotton, to synthetic, to mixed cotton-synthetic.

After the 28 hours were up, a panel of seven people -- who were picked specifically because of their sensitivity to odors -- sniffed the T-shirts. They rated the pleasantness of the odor of the polyester shirts lower than that of the cotton shirts. Specifically, "polyester clothing after the spinning session smelled significantly less pleasant, and additionally, more intense, more musty, more ammonia, more strong, more sweaty and more sour," researchers wrote in the study, and the "qualitative differences were the largest for the sourness, strongness and mustiness."

The big takeaway from this study? Definitely wash those dirty gym clothes -- ASAP.

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