Drop 1 is Merino Gym Shorts, in a Founding Run of 100. Join the waitlist below to get first access when it opens.
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Our Story
Why Certamen Exists.
Who's building it, what the name means, and why it starts with what you train in.
Who's building this
Built by an Insider, Not an Expert.
I'm Ben. I'm 18, I'm from Australia, and I train the same way most guys reading this do. Training locked in. Sleep tracked. Macros tracked. Bloodwork done.
Certamen didn't start with a health scare. It started with me going deep on my own health and finding the one thing nobody was talking about.
The Name
Certamen
A contest, competition, battle or struggle.
Why the Name
I named the brand Certamen because that's how I see men's health right now: a struggle most guys don't know they're in. Research suggests men's testosterone has been declining for decades, and some of what's driving it may be built into everyday life.
Certamen is about choosing to compete for your health. Not out of fear. Through better choices: how you train, how you sleep, what you eat, and what you wear while you do it.
Our Motto
The Struggle Is Natural.
Certamen means struggle. Most brands sell you a way around it. I think the struggle is the point.
Training is a struggle. So is sleeping right, eating right and saying no when it's easier to say yes. That's not something to escape. It's how men have always built themselves, and it's natural.
So is what we make. Natural fibres, for men building their health the natural way, without shortcuts.
What I found
The Research Was Sitting in Plain Sight.
While researching what actually moves testosterone and fertility, I kept running into the same thing. Peer-reviewed studies linking synthetic fabric, microplastic exposure and hormonal health. No major activewear brand talks about it.
The Polyester DefaultSee the Research
Big Brands Never Asked If It Was Healthy. Only If It Was Cheap.
Nike, Gymshark, and Lululemon build most of their gymwear from synthetic, petroleum-based fabric, not because it performs better, but because it's cheaper to produce and easier to dye and print on.
That gym kit sheds microplastics when you wash it and when you move in it. Research is starting to show where those particles end up. We call this The Polyester Default: an industry norm nobody stopped to question.
Fibre-First training
Choose Your Gym Kit Like You Choose Your Food.
You already think about what goes into your body. Food, sleep, supplements. Fibre-First training applies the same thinking to what you wear while you train.
That's why Certamen is built from Organic Cotton and Merino Wool, not polyester. Merino matches or outperforms synthetic activewear on moisture-wicking, odour resistance and temperature regulation.
The Other Options
Most Natural Alternatives Stop at the Fabric.
Swapping polyester for something natural isn't rare anymore. What's rare is a brand that treats the fabric as the starting point, not the whole pitch.
- ✗Vague health claims with no research behind them. You're asked to just trust them.
- ✗Built from trendy materials like bamboo that look good on paper but aren't functional, and don't hold up in the gym.
- ✗Built around sterile minimalism. No meaning behind the brand, nothing to actually feel.
Certamen was built to close all three at once: backed by real research, made for the gym you actually train in, and built around a brand that has meaning.
What I stand for
Five Things Certamen Won't Compromise On.
- ✓Evidence over vague wellness marketing. Every claim links back to a source.
- ✓Clothing is a training input, not an accessory.
- ✓You don't need to be an outside expert to build something real.
- ✓Straight answers about the science, caveats included.
- ✓Simple Clothing, never shallow.
Why nowJoin the Founding 100
I'm Not Waiting Until I Feel Qualified.
My generation is fighting for its hormonal health. Somebody has to build the gym kit that takes it seriously. I'd rather start now, with you, than wait.
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The Shop Opens with the Founding 100.
Drop 1 is Merino Gym Shorts, in a Founding Run of 100. Join the waitlist below to get first access when it opens.
Average male testosterone has dropped 54% since 1972
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Your Clothing Is the One Gap Left.
You've fixed your training. Your sleep. Your diet. The last stone left unturned is hanging in your gym bag: soaked in polyester.
Join the Founding 100Loading spots...
Free to join. No payment until it ships.
Before You Join
Straight Answers, No Spin.
Not yet. We're in the validation phase and currently selecting suppliers for Organic Cotton and Merino Wool. Founding Members lock in early access and pricing before that process finishes, not a finished product today.
We link the primary source wherever a specific study backs a claim, so you can read it yourself. No single study proves polyester alone causes infertility. These are separate findings, from animal studies, lab research, and population data, that consistently point the same way, and we say so rather than overstating it.
Merino Wool matches or outperforms synthetic activewear on moisture-wicking, odour resistance, and temperature regulation, without shedding microplastics in the process.
No. Joining reserves your spot in the Founding 100 for free. You only pay if and when you decide to place an order once Certamen launches.
Most natural fibre brands stop at "clean" or "non-toxic," with no sources attached. We link the primary, peer-reviewed research behind every claim, including the caveats, and we're building this specifically around men's hormonal and fertility health, not general wellness.
We're finalising a supplier for the Organic Cotton and Merino Wool before locking in a date. Founding Members hear about progress first, and get first access the moment it's ready.
We're still finalising exchange and return details ahead of launch, but getting the fit right for you is a priority, not an afterthought. Founding Members get a say in sizing before production locks in.
The Research
Read It Yourself.
Every claim we make links back to the study it came from. Tap a card to read the source.
Toxicological Sciences · 202423 / 23human testes tested contained microplastics
Toxicological Sciences · 2024
Microplastics in Every Human Testis Tested
Researchers tested 23 human and 47 dog testes. Microplastics turned up in every sample. Higher PVC and PET levels were linked to lower testicular weight.
Read the study ↗PubMed · Nanoplastics study200B+nanoplastic particles per gram of fleece
PubMed · Nanoplastics study
Synthetic Fabric Sheds Nanoplastics
One gram of fleece released an average of 210 billion nanoplastic particles from abrasion alone. The first study to show significant polyester nanoplastic release from textiles.
Read the study ↗Environmental Pollution · 2024500×more fibres from wear than washing, in some fabrics
Environmental Pollution · 2024
Training in It Sheds More Than Washing It
Everyday rubbing and movement can release far more fibres than the washing machine. Sportswear is named as a high-abrasion category, alongside socks and underwear.
Read the study ↗Toxicology Reports · 2026Reviewof microplastics and male reproduction
Toxicology Reports · 2026
Hormones, Sperm and Testicular Health
A review of the evidence found microplastics can affect testicular structure, hormone balance and sperm quality. Much of the evidence comes from animal and lab studies.
Read the study ↗IJERPH (MDPI) · 2021PFASand phthalates in textile finishes
IJERPH (MDPI) · 2021
The Chemicals That Come with Synthetics
Water-repellent PFAS coatings and phthalates in plastic prints are known endocrine disruptors. Skin-contact exposure from everyday Clothing is still under-studied.
Read the study ↗Contraception · 199214 / 14men reached zero sperm count
Contraception · 1992
The Polyester Sling Study
14 men wore a polyester scrotal sling for 12 months. All reached a zero sperm count, and counts returned to normal after they stopped. A small, older study, but a striking one.
Read the study ↗NEJM · 20244.53×higher risk of heart attack, stroke or death
NEJM · 2024
Microplastics in Artery Plaque
257 patients were followed for 34 months. Those with microplastics in their artery plaque had a higher risk of heart attack, stroke or death. The authors say it doesn't prove cause, and it isn't about Clothing specifically.
Read the study ↗PubMed · 1996vs cottonpolyester underwear compared with cotton and wool
PubMed · 1996
Polyester Underwear and Sexual Activity
Men wearing polyester or polyester-blend underwear showed a drop in sexual activity that grew over time, compared with men in cotton or wool. A small, older study.
Read the study ↗PubMed · 1993Not heatthe researchers ruled heat out as the cause
PubMed · 1993
Why Polyester, Not Heat?
In a dog study, researchers ruled out heat and pointed to the electrostatic charge polyester builds up against the body. An animal study, so treat it with care.
Read the study ↗This is an emerging field. No single study proves that polyester alone causes infertility. Several of these findings come from animal or lab studies with small sample sizes. They point in the same direction, and we're not going to pretend it's more settled than it is.
Contact
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