Why Your Gym Clothes Smell Absolutely Horrible

Last Updated on March 31, 2024

Readjusting to the new normal will be difficult, so don’t make it worse than it has to be. If you’re an avid gym-goer, make sure you follow the proper gym etiquette. And I’m begging you, please, don’t be the person whose gym clothes smell.

Sure, everyone stinks a bit when they exercise, but there is always that person — man or woman — who smells like they haven’t taken a shower in a weak. You can usually catch a whiff of their body odor all the way from the stretching area!

Still, I’m not here to smell-shame anyone but to simply offer a bit of advice on why your gym clothes smell horrible. I’ve sniffed out the science behind body odor and investigated the best materials for odor-resistant gym clothes (Merino wool, wink, wink). I’ll also suggest a few of my favorite activewear apparel that stays fresh (for both men and women), even when you don’t.

Sniffing Out The Truth Behind Body Odor

Alright, let’s take a step back here and figure out why you smell.

It’s a common assumption that when your foul-smelling, musty B.O. simply radiates from your body when you work out. Basically, if you sweat, you smell. 

But that’s not exactly the case. And the truth is a little more disgusting.

It’s hard to imagine, but you have millions of bacteria living on your skin. For these microorganisms to survive, they must eat. And what do they snack on? Your sweat, of course! The proteins and other nutrients in your sweat provide fuel for the bacteria. They digest these sweat nutrients and output what we know as body odor in the form of volatile organic compounds (VOCs).

In other words,   bacteria snack on your secretions and fart out a nasty smell. Crazy, right?

That’s not all, though. These bacteria thrive and multiply in warm, moist areas of your body. Thus, the more bacteria, the worse the smell. That’s why places like your armpits, feet, and pelvic region, stink worse than the rest of your body. Gross — I know — but it’s the truth. Okay, Okay, now here’s where it gets even more tricky.

Your gym clothes, no matter how non-odorous they may seem, still have tons of bacteria on them from your previous workout session. This is especially true if you stuff them in a wet duffel bag in your trunk. Thus, when you start to sweat again, both the bacteria on your skin and your clothes create one big mega cloud of body odor.

Just to quickly recap, bacteria eat the nutrients in your sweat. They emit a smell in the form of volatile organic compounds (VOC), and that’s why you smell.

So, Why Do Your Gym Clothes Smell?

Well, hopefully, by now, you understand that your body odor is not your body odor; it’s the bacteria. So the key is to control the bacteria, thus controlling the smell.

But, there is one missing element: why do some clothes smell after being washed?

Well, the science gets even more fascinating. Typical synthetic materials like nylon and polyester (like an Under Armour shirt) are naturally quick-drying. Thus, when those VOCs are released, they become trapped in the fabric structure itself. It’s not just the bacteria producing the smell but also the odor itself sticking to the fabric’s microstructure.

And that’s where Merino wool comes in.

Unlike synthetics, Merino wool has a high moisture absorption capacity. The hydrophilic keratin structure (the same as human hair) invited moisture to become trapped within the fibers. So much so, it can hold up to 30% of its own weight in water without feeling wet.

Therefore, when those pungent bacterial VOCs make it to the Merino fabric, they gravitate toward the moisture and not the material itself. In other words, your body odor gets trapped in the water vapor. Once that moisture evaporates, the smell leaves with it, and your clothes remain fresh.

Think about it like a toilet. If you go number two without any water in the bowl, it’s going to smell a lot worse. I know it’s a gross analogy, but it exemplifies the science pretty well.

Additional Evidence: The Dry Test

To further exemplify this point, the good people over at Besthiking.net did a dry test when comparing different hiking t-shirts. They found that the synthetic blend was the quickest to dry, which is suitable for some applications. But, if you’re worried about odor, the faster it dries, the more likely it will stink.

You can learn more about this experiment in our piece The Disadvantages of Merino Wool. For now, here are a brief summary of the results.

Note: If you’re looking into purchasing a Merino wool t-shirt but are worried about its moisture management properties, you shouldn’t be. The fabric itself may absorb water vapor and sweat, but it doesn’t actually feel wet. AS previously mentioned, studies have shown it can hold about 30% of its own weight in water while still feeling dry to the touch.

Final Note About Why Your Gym Clothes Smell

To sum up, the millions of bacteria on your skin and clothes eat the nutrients in your sweat and excrete what we know as body odor. To control this odor, you should first keep yourself clean and then make sure your clothes stay fresh by wearing Merino wool.

Even though Merino wool is odor-proof, that doesn’t mean that you are. No amount of clothing will make you not stink at the gym if you aren’t already clean. So, make sure to take a quick rinse in the shower before (and after) hitting the gym to stay fresh all day.

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If you have any questions, concerns, or corrections, feel free to contact us, as well.