Is training in polyester actually a problem, or is it overblown?
What the studies measured in polyester and sweat, what they did not, and the training shirt we made with no plastic in it.
It usually happens in the changing room. You pull the shirt over your head, it sticks for a second, and the tag is right there. Polyester. You already knew. You know what polyester is, you stopped microwaving in plastic years ago, and you still put this on four times a week and heat it against your skin.
“I’d prefer not to wear it, but all my gym clothes contain polyester.”
If that is you, two things have kept the gym bag as it is. You are not sure it matters. And you assumed there was nothing else to train in. This page takes them one at a time, and then shows you the PRFORM Apex tee: a training shirt made of one fibre, 100% merino wool, with no polyester, nylon or elastane in it.
You did not miss anything. The training rack only ever offered plastic.
Walk into any sports shop and read ten labels. Polyester. Nylon. Elastane. The words on the front change: technical, performance, moisture-wicking, recycled. The composition line does not. You trained hard and you bought what the best brands put in front of you, and all of it was the same three fibres.
“‘Tech wear’ is a way for brands to sell cheap polyester at high margins - change my mind.”
So the worry got parked. Not because you stopped caring, but because the one garment you sweat in was never offered to you in anything else.
What people try first, and why it does not hold
Recycled polyester. It is the easy switch, and it is the same fibre with a better story.
“I’m seeing so many 2026 “eco-drops” that are just rPET (recycled plastic bottles) disguised as luxury activewear.”
Cotton. An honest fibre and a good one. It is just not what most people want to train in.
“Cotton is healthier for the skin, but it stays drenched all day.”
The “merino” training tee. You go looking for wool, flip the care label, and find a blend. One buyer’s words: “sure, the wool they used was 100% merino, but the garment itself was 47% Nylon and feels and wears like scratchy polyester”. The fix for a plastic problem cannot be more plastic.
Doing nothing. The most common answer, and a fair one if you believe it does not matter. So here is what has actually been measured.
So is it overblown? What was measured, and what was not
“Is polyester activewear actually bad for your health or is it overblown?”
It is the right question, and the honest answer has two halves.
Scientists at the New York State Department of Health found bisphenol A in 82% of 77 clothing and textile samples tested, with the highest level in a 97% polyester sock (Xue et al., Environmental Science & Technology).
Researchers at the University of Plymouth and Italy’s National Research Council found that polyester garments release microfibres into the air simply by being worn, in yearly quantities of the same order as those released to water by washing (De Falco et al., Environmental Science & Technology).
Laboratory studies show that bisphenols and antimony present in clothing migrate into artificial sweat, and that antimony release from polyester rises with temperature (Biver et al., Regulatory Toxicology and Pharmacology, 2021).
Here is what those studies do not say, because we will not pretend otherwise: nobody has shown that a shirt changes your hormones. What they say is narrower and harder to argue with. The compounds are in the fabric, and heat and sweat move them. Training is the one hour a day when a shirt is hot, wet and pressed against you.
The smell that survives the wash is the plastic holding it
You know the shirt. It comes out of the machine smelling of nothing, and ten minutes into the warm-up it is back. The mechanism is not a mystery. The oily compounds your skin produces when you sweat bind to the surface of plastic fibres, and washing struggles to pull them back out.
Researchers at Ghent University found that after a spin class, polyester shirts smelled significantly more intense and less pleasant than cotton shirts, with odour-associated bacteria growing almost only on the polyester (Callewaert et al., Applied and Environmental Microbiology).
University of Alberta researchers found polyester released the highest intensities of odorous sweat compounds after 24 hours, while wool and cellulosic fibres released less after three hours (McQueen et al., Textile Research Journal). Funded by a national science council, not a wool board.
So if you have ever quietly suspected your washing machine, your detergent or your own body: it was never any of those. The smell lives in the fibre, and the people who train in it worked that out years before any brand said it out loud.
“Polyester smells like death after one gym session and I’m done with it.”
“Marketing gaslighting makes people belive that if their clothing stinks, that means that there is something wrong with THEM [...]”
“I didn’t know that polyester binds to fatty acids, that explains a lot!”
The internet has a whole folklore for fighting it. Vinegar soaks, sport detergents, strip washing, sixty-degree cycles the label warns against, the freezer trick. Some of it helps for a wash or two. None of it holds, because none of it changes the surface the compounds bind to.
Wool works the other way round. It takes the compounds into the fibre and lets them go as it airs, which is why merino wearers hang a shirt up at night and put it back on in the morning. Train Monday, hang it up, train Wednesday in the same shirt, and nobody at the next bench knows.
Read our labelSo the problem is not your sweat, your detergent or how often you wash. It is the fibre. And that is the one thing in this whole subject you can change with a single purchase.
A training shirt with no plastic in it
The Apex tee is one fibre all the way through. 100% merino wool in the body, and the same merino knit more open in the mesh panels at the sides and down the back. No polyester, no nylon, no elastane. Here is what the shirt is, line by line.
- 100% Australian merino woolOne fibre on the label. No polyester, no nylon, no elastane.
- Ø 17.5 micronSuperfine, the grade for bare skin. Reads as soft, not as wool.
- 160 g/m²A training weight. Light enough for the session, warm enough at rest.
- Merino mesh panelsAirflow where you heat up, still one fibre.
- Wash cold, non-bio, hang to dryThe care line that keeps a merino tee whole.
- Designed in NorwayBuilt for training, worn everywhere.
Where plastic holds the sweat compounds at its surface, wool takes them into the fibre and lets them go as it airs. So the routine flips:
The session does its worst.
Air is the wash cycle.
Ready before you are.
PRFORM started with a contradiction. I had taken plastic out of my kitchen, out of my water bottle, out of most of my life, and I was still putting it on for the one hour a day I sweat hardest, then heating it against my skin. I built the shirt I could not find.
We are new, so there are no customer reviews on this page and we will not invent any. What exists is what people who already own 100% merino tees say about the fibre:
“I wear this shirts for climbing, sweat a lot, heng them to dry and can wear one shirt for 3-4 times till it starts to smell.”
“Also, I can wear them for a week at a time without them ever smelling.”
The four questions everyone asks before they buy
Straight answers, including the one that loses us a few sales.
Will it survive the gym?
“After a year my $160 dollar t-shirts self destructed with holes and the shirts were then of no use.”
That is the fear, and it is earned. Any 160-gram knit wears where it is rubbed hardest, and the two things that open a merino tee early are abrasion under pack straps and enzyme detergents, which digest protein. So the care line is on this page and on the product page.
Isn’t wool hot?
“Lol wool is warm wet or dry , cool in the summer and warm in the winter [...]”
We answer it with a weight, not with physics. 160 grams per square metre is the light end of merino, a training weight. And the honest limit: if you run very hot at very high output, a merino tee is not your fastest-drying option, and we would rather say so here than in a returns email.
There is no elastane. Does it move?
“100% wool is still not great for something fitted that needs really good recovery.”
True, and we did not build a fitted one. This is a knit, so it stretches with you and comes back, and the mesh panels are knit more open where you heat up. It is cut as a training tee, not as compression. If you want a compression fit, this is the wrong shirt, and we would rather lose the sale than the trust.
How does it fit, and what if it does not?
The cut is athletic and it comes in S, M, L and XL. If you are between sizes, take the larger one. It ships from Norway. And the return is simple: 30-day returns, unworn and with the tags on. Try the fit at home, read the label, and if either is wrong send it back with the prepaid label.
900 kr for one tee, and it replaces a drawer of them
Flip the label on a $150 “technical” tee and on a $15 one from a fast-fashion site. The same polyester. Most of what you pay for in tech wear is the story, and the forums worked that out before we did:
“‘Tech wear’ is a way for brands to sell cheap polyester at high margins, change my mind.”
Ours is 900 kr, more than a polyester tee, and here is what the money buys. Superfine merino at 17.5 micron, which is the expensive end of wool. One shirt that trains all week and gets washed on Sunday, so it replaces a drawer of tees rather than joining it. Put it next to what it replaces: the $160 merino tee that holed, the polyester tees you rebuy every year, the arsenal under the sink. And doing nothing costs the same hour of plastic every session, plus the rebuys.
The return: 30-day returns, unworn and with the tags on. Read the label and try the fit at home. If either is wrong, send it back with the prepaid label.
The two fibres, side by side
Strip the marketing off both and this is the comparison that is left.
Polyester
- holds the odour compounds longest of the fibres measured
- sheds plastic every wear and every wash, and the plastic stays
- back in the machine after every single session
Merino
- takes odour compounds in and lets them go as it airs
- sheds wool, which is protein and breaks down
- hang it up tonight, wear it again tomorrow
Smaller questions
Is merino itchy?
Itch tracks fibre thickness, and ours is superfine: 17.5 micron. If your reference is a school jumper, this is a different material in everything but name.
How do I wash it, and how often?
Far less than you think. Hang it up at night and the shirt resets itself; train in it all week, wash it on Sunday. When you do: cold, a non-bio detergent, no dryer. Biological detergents contain protease, which digests protein, and wool is protein.
Why not just cotton?
Nothing wrong with cotton. We built this for the hour most people did not want to spend in it: the session. If you train in cotton and like it, you do not need us.
What are the blue panels?
Merino mesh, knit more open where you heat up. Still one fibre: no polyester, no nylon and no elastane on the label.
The Merino Tee
One shirt with a label you can read in full. Knit in a single fibre, designed in Norway for people who train, and for the days between.
“[...] cleaner clothes are frequently un comfortable or very expensive and don’t come in gym versions lol”This is the gym version.
The Merino Tee
100% superfine merino wool, 17.5 micron, 160 g/m². No polyester, no nylon, no elastane. Air it overnight, wear it again. It costs more than a polyester tee, and it replaces a drawer of them.
Two ways this goes
You can keep training in the shirt whose tag you have stopped reading, and keep the worry parked where it has been. Or you can take the plastic out of that one hour, with a shirt you can send back unworn inside 30 days. That is the whole decision.
Get the tee 30-day returnsQuotes on this page are from public forums and comment sections about synthetic and natural fibres in general, word for word. Studies are cited as published; none of them tested this shirt.