The dirty secret the activewear industry doesn't want you to know...
Why Researchers Are Warning Men About Their Gym Shorts
Brian S.
Wellness Researcher
New studies are raising red flags about what polyester activewear is actually doing to your body — and most guys have no idea.
Here's something most men never think about: the athletic shorts you wear to the gym, on a run, or in the sauna are almost certainly made from polyester.
That matters more than you think.
Polyester is plastic. Literally — it's made from the same petroleum-based compounds as plastic water bottles. And like all plastics, it sheds. Every time you move, stretch, or sweat in polyester shorts, thousands of microscopic plastic fibers break loose from the fabric.
Those fibers don't just float away. They land on your skin. They settle into your pores. And in the groin area — one of the most absorptive and temperature-sensitive regions of the male body — they make direct contact with tissue that was never meant to be exposed to synthetic materials.
This isn't speculation. It's becoming one of the most quietly alarming findings in men's health research.
Here's What The Research Says...
1. Polyester is Plastic
Most "performance" shorts are made from polyester — a petroleum-based synthetic fabric. It's essentially the same plastic compound used to make water bottles and food containers. And like all plastics, it sheds. Every time you move, stretch, or sweat, thousands of microscopic plastic fibers break loose from the fabric and land directly on your skin.
2. And Many Popular Brands Contain high levels of toxic "Forever Chemicals"
Independent lab testing has found that over 100 popular activewear brands contain BPA — an endocrine disruptor linked to hormonal imbalance and reproductive harm. Some tested at levels 40x above recommended safety limits. On top of that, many polyester fabrics are treated with PFAS (per- and polyfluoroalkyl substances) to create "moisture-wicking" properties. These are the same "forever chemicals" that have made national news for contaminating drinking water.
3. These Same Chemicals Have Also Been Linked to Hormone Disruption
BPA, PFAS, and phthalates — all commonly found in synthetic activewear — are classified as endocrine disruptors. That means they can interfere with your body's natural hormone production, including testosterone. Emerging research has linked chronic exposure to reduced T levels, thyroid dysfunction, and long-term reproductive issues in men.
4. And research shows your body can absorb these chemicals - especially when sweating
Here's the part most guys don't think about: the groin area is one of the most absorptive regions of the male body. Research shows scrotal skin absorbs chemicals at significantly higher rates than other skin. When you exercise, your body temperature rises, your pores open, and the fabric is pressed directly against this tissue. Researchers describe these as ideal conditions for chemical transfer from fabric to skin.
5. Not Only That - Polyester Has Also Been Shown To Lower Sperm Count
A widely cited study from the European Society of Human Reproduction found that men who wore polyester underwear experienced a significant decline in sperm count — in some cases dropping to functionally zero. When the polyester was removed, counts recovered. Separately, a 2024 University of New Mexico study found microplastics in 100% of human testicle samples tested — at concentrations nearly 3x higher than other organs.
The Part Nobody In Fitness Is Talking About...
Think about your routine for a second.
You probably track your macros. Maybe you take a greens supplement. You've optimized your sleep. You might wear a WHOOP or an Oura ring. You spend hundreds a month on things that are supposed to make you healthier and perform better.
Then you pull on a pair of shorts made from the same material as a plastic bottle, and go sweat in them for an hour.
Your pores open. Your body temperature rises. The fabric is pressed directly against your skin — against the most vulnerable and absorptive tissue on your body. And the whole time, that fabric is shedding microscopic plastic particles and leaching chemical compounds that researchers are actively studying for their effects on male hormones and fertility.
You'd never drink water from a plastic bottle that had been sitting in a hot car. But you're essentially doing the same thing to your skin — in the place that matters most — every time you work out in polyester.
It's the one blind spot in an otherwise optimized routine. And most guys don't even know it exists.
So What's The Alternative?
The obvious question is: if polyester is the problem, what should you be wearing instead?
The answer isn't complicated. Men wore natural fabrics for thousands of years before synthetic materials were invented in the mid-20th century. Cotton. Wool. Linen. These materials don't shed microplastics, don't contain BPA or PFAS, and don't require chemical treatments to perform.
The challenge has been that most "natural" athletic brands make products that look and feel like what you'd buy at a farmer's market — boxy, rough, and nothing like the fitted, stretchy performance wear guys actually want.
That's starting to change.
A growing number of companies are engineering natural fibers to compete with synthetics on fit, stretch, and moisture management — without any plastic. One brand that's gained significant traction is Ryker, which makes athletic shorts from 100% organic cotton with a 100% merino wool built-in liner.
What Makes Ryker Different
Ryker's approach is straightforward: replace synthetic fabrics with natural alternatives that perform better - and aren't loaded with toxins.
The outer short is made from 100% GOTS-certified organic cotton. It's soft, breathable, and surprisingly stretchy thanks to a specialized knitting technique that gives natural cotton the flexibility you'd normally need spandex for. No polyester. No nylon. No spandex.
The built-in liner is where it gets interesting. Instead of the standard polyester mesh compression liner found in virtually every major activewear brand, Ryker uses 100% merino wool. Merino is naturally temperature-regulating — it wicks moisture away from the skin naturally. It's also naturally antimicrobial, meaning it resists odor-causing bacteria. You can wear these multiple times between washes without them smelling.
Third-party tested. Every batch of Ryker's fabric is independently lab-tested and certified free of BPA, PFAS, phthalates, and formaldehyde. They hold both GOTS and OEKO-TEX Standard 100 certifications — two of the most rigorous textile safety standards in the world.
And they actually fit like Lululemon or Vuori — same athletic cut, zipper pockets, range of inseams. You wouldn't know they were natural fiber by looking at them or wearing them. You'd only know by what's not happening against your skin.
Over 100,000 pairs sold · 4.9-star average across 5,000+ reviews · Endorsed by Ben Greenfield and a growing list of health-focused creators.
How They Compare
Fabric
Breathability, Sweat Wicking & Odor Resistance
Toxic Chemicals
Microplastic Exposure
100% organic cotton +
100% Merino wool
Naturally breathable, Merino wicks sweat & fights odor
3rd party tested + OEKO-TEX Certified
Protects from Microplastics
"The Other Guys"
100% Plastic (polyester, nylon, spandex)
Polyester traps heat, sweat & odor causing bacteria
Often contains high levels of BPA, Phlates and PFAs
Loaded with Microplastics
The choice is clear - you shouldn't be wrapping yourself in toxic plastic shorts all day.
Natural Fiber Gym Shorts With A Compression Liner
The Apex Short - (100% Organic Cotton + 100% Merino Wool Liner)
100% organic cotton short + 100% Merino wool liner
Fits just like Lululemon shorts
Naturally stretchy, temperature regulating and odor resistant
$99.00
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THE APEX SHORT
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Description
- 100% organic cotton shorts + 100% Merino wool liner
- Organic cotton from GOTS-certified sources
- Made with fabrics from OEKO-TEX Standard 100 certified mills
Enough with the polyester shorts with toxic 100% plastic underwear liners. Switch to our natural Apex shorts.
Guaranteed to be the most comfortable gym short you've ever worn.
Materials and Care
Shorts: 100% Organic Cotton
Liner: 100% Merino Wool
Care Instructions: Machine wash cold on gentle setting. Wool specific setting if available. Gentle washing avoids shrinking & felting.
Lay flat to try. Do not tumble dry.
Wash only when needed.
Size Chart
Runs small - we recommend sizing up!
Shipping & Returns
FREE Shipping on orders $150+
If you don't love it, return in 90 days for a full refund.
Trusted By Top Health Experts And Biohackers
Why High Performers Are Switching...
MH
Mark H.
Founder & CEO
Miami
I optimize everything else. This was my one blind spot.
"I spend $600/month on supplements, recovery, and bloodwork. I track every input that goes into my body. Then I realized I was spending 4 hours a day training in petroleum-based plastic that's been linked to hormone disruption. Once I saw the data on polyester and endocrine disruptors, I couldn't unsee it. Switched to Ryker, and I won't go back. These are now a non-negotiable in my protocol."
MH
William T.
Managing Director
New York
I looked at the research. The decision was obvious.
"I don't buy anything based on marketing alone. I looked at the actual studies on polyester, microplastics, and BPA - and the data is hard to argue with. Ryker's third-party lab results showing zero endocrine disruptors sealed it for me. The Merino liner is genuinely more comfortable than any synthetic I've worn. These are the only shorts I train in now."
MH
James G.
VP, Technology
San Francisco
The last gap in my health stack.
"Eight Sleep, WHOOP, my sauna - I've invested in all of it. But I was still training in polyester shorts that shed microplastics. It's absurd when you think about it. Ryker closed the last gap. The fit is identical to Lululemon, the Merino liner handles sweat better than any synthetic, and I'm not absorbing endocrine disruptors through my skin for two hours a day. Should've done this years ago."
Done wearing plastic to the gym?
Make the switch to Ryker.
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