★★★★★ Over 30,000+ Shorts Sold

7 REASONS YOUR GYM SHORTS ARE KILLING YOUR TESTOSTERONE

SHOP NERO MERINO SHORTS See the 7 Reasons ↓

25%

Men's testosterone has dropped 25% in the last 20 years

92%

Of gym shorts are made from polyester plastic

0

Brands talking about what that's doing to your body

REASON #01

Your gym shorts are made from the same plastic as a Coke bottle.

Polyester isn't really a fabric. It's a plastic, the exact same material used to make disposable water bottles, melted down and spun into fibre. Every time you wear it, you're pressing that plastic directly against one of the most sensitive parts of your body.

REASON #02

That plastic contains chemicals that tell your body to produce less testosterone.

Polyester contains a group of chemicals called phthalates. These chemicals act like a signal to your body to slow down testosterone production. Your body reads them as a reason to make less of the hormone you're training to boost.

REASON #03

Tiny plastic particles from your shorts are being found inside men's testicles.

Your balls absorb chemicals 12x faster than the rest of your body. Every time polyester is worn or washed, it sheds plastic particles. Scientists in 2023, confirmed they've been found accumulating inside testicular tissue, where they damage the cells responsible for producing testosterone and healthy sperm.

REASON #04

Polyester traps heat exactly where your body needs to stay cool.

For your body to produce testosterone and healthy sperm properly, your testicles need to stay a couple of degrees cooler than the rest of you. That's literally why they hang outside the body. Polyester traps heat and holds moisture against the skin, the worst possible combination for that area of your body.

A study of 656 men found that those who wore breathable, natural fabrics had 25% higher sperm count than men who wore tight synthetic alternatives.

REASON #05

Working out is actually the worst time to be wearing plastic against your skin.

When you exercise, your pores open up to let sweat out. That's also when they're most open to letting things in. Sweat acts like a solvent that pulls chemicals off the fabric, and your open pores absorb them straight into your bloodstream.

REASON #06

Men's testosterone has been crashing for decades and scientists think plastic chemicals are a big reason why.

A 2021 study of over 4,000 men confirmed that young men today have nearly 25% less testosterone than young men did 20 years ago. Doctors and researchers keep pointing to plastic chemicals in the environment as one of the main things they can't otherwise explain.

REASON #07

Gym brands know. They just make more money saying nothing.

Polyester costs about $2 per meter to make. Merino wool can cost up to $50 per meter. That's why 92% of gym wear is polyester. Not because it's better for you. Because it's better for their margins. The silence isn't an accident, it's a business decision. You're cheaper to keep uninformed.

SO WHAT DO YOU WEAR INSTEAD?

Nero shorts are made with a New Zealand merino wool Liner and organic cotton shell. No polyester. No plastic chemicals. No microplastics shedding against your skin.

Here's what that actually means:

No plastic chemicals against your body

No phthalates, no BPA, nothing that interferes with your hormones.

Sweat moves away from your skin

Merino pulls moisture away from the body. Polyester pushes it back toward you.

No microplastics

Natural fibres don't shed plastic particles. Full stop.

Your body stays at the right temperature

Merino wool naturally regulates heat, keeping things cooler where they need to be cool.

Sourced responsibly

New Zealand RWS-certified merino. Certified organic cotton. Nothing hidden in the supply chain.

99-DAY MONEY-BACK GUARANTEE

Wear them for 99 days. If you don't love them, or if you don't feel the difference, return them for a full refund. No forms. No questions. No hassle.

We're that confident.

I WISH I'D TRIED THEM SOONER

“Best Shorts I’ve Ever Owned”

I bought the Nero Shorts and I can confidently say they’re the best shorts I’ve ever worn. The material is next-level, breathable, soft, and somehow manages to feel both lightweight and durable at the same time. The fit is perfect and they move with you without ever feeling bulky or stiff. They’ve quickly become my go-to for everything from casual wear to lounging, and I genuinely notice the quality every time I put them on.

“Comfy and Practical”

These are some of the best shorts i’ve ever worn! Comfy, good pocket size, sits well on the booty! The merino on skin is really cosy, while the cotton outer always looks good!
Finally found a pair of shorts that are good for me and the earth!

Great Shorts

Great shorts, very comfortable and i have not overheated whilst working out doing crossfit or gym.

“So Comfortable”

Great for running in. While they were in the wash I went for a run in some polyester shorts that were nearly the same price and the seam almost cut my sack to shreds. You cannot go back once you have tried these awesome shorts. I ordered another couple of pairs which arrived just as quickly. I wore the same pair on consecutive days for running and they didn't smell at all afterwards.

“Buying More Soon”

I never noticed how restrictive and uncomfortable polyester was until I tried Nero. Sometimes, when I'm forced to wear my polyester gym shorts again, it's actually horrible lol.

YOU TRAIN HARD. WHAT YOU WEAR SHOULD WORK WITH YOU, NOT AGAINST YOU.

Every session in polyester is a session where the very thing you're trying to build, testosterone, strength, performance, is being quietly undermined by what's pressed against your body.
You deserve better than a Coke bottle with a waistband.

SHOP NERO MERINO SHORTS

★★★★★ 4.8/5 (550+ Reviews)

Over 30,000+ Shorts Sold

Nero prices increase every Monday as wool costs rise. Today's price won't be here next week.

Inseam	Waist
5" - 7"	28-30" (S)
5" - 7"	30-32" (M)
5" - 7"	34-36" (L)
5" - 7"	38-40" (XL)
5" - 7"	42-46" (XXL)