Fitness Clothing Manufacturers in China: How to Test Fabric (2026)
Quick answer: With activewear, you are really choosing a fabric, and the factory is the one that sews it. Before you compare prices, get each supplier's fabric spec in writing: fiber blend, weight in GSM, knit type and stretch. Then test samples the way customers will use them: a squat test for see-through, a wash test for shrinkage and stretch recovery, and a sweat test for color bleeding. Ask the factory or its fabric mill for lab results on wicking, colorfastness and pilling. Keep your product claims modest: "anti-odor" and "UPF 50+" each need evidence, and "antibacterial" can trigger US pesticide rules.
Why activewear is a fabric decision first
Two factories can sew the same pair of leggings to the same pattern and get very different reviews. The difference is usually the fabric: how dense the knit is, how much spandex is in it, and how well the dye holds up to sweat and washing. Most garment factories buy fabric from a mill rather than knitting it themselves, so ask early: who knits and dyes this fabric, and can you get me the mill's test report? A factory that can answer is easier to hold to a standard on every reorder.
The fabric spec to get in writing
| Spec | What to ask for | How to check it |
|---|---|---|
| Fiber blend | Exact percentages, e.g. nylon/spandex or polyester/spandex | Must match your label; a lab can test fiber content |
| Weight (GSM) | Grams per square meter of the finished fabric | Weigh a cut swatch; a figure "in writing before sampling" stops quiet downgrades |
| Knit type | Interlock, jersey, rib, seamless circular knit, brushed or not | Compare against your approved swatch |
| Stretch and recovery | Results to ASTM D2594, the method for stretch knits | Lab report; then your own wash test |
| Moisture handling | AATCC 195 (moisture management) or AATCC 197 (vertical wicking) | Lab report, ideally before and after washing |
| Colorfastness to sweat | AATCC 15 (acid perspiration) | Lab report; white-cloth rub test on samples |
| Pilling | ASTM D4970 (Martindale) or ASTM D3512 | Lab report; check inner thighs on worn samples |
You don't need every test for every product. A $15 tank top and a $70 pair of leggings justify different budgets. But the spec sheet costs nothing, and it is the document you compare reorders against.
Nylon or polyester?
Most activewear is one of two blends, each with spandex for stretch:
- Nylon/spandex feels softer and, at the same weight, generally looks more opaque. It usually costs more and is the common choice for premium leggings and yoga wear.
- Polyester/spandex dries quickly, holds color well and is the only base that takes sublimation printing, so it suits all-over prints and high-sweat training gear. It typically needs a heavier fabric to be as opaque as nylon.
Whichever you pick, color changes the result. A fabric that passes the squat test in black can fail in pale pink or grey.
A sample routine for leggings, shorts and sports bras
- Measure first. Check the sample against your size spec at waist, hip, rise and inseam before anyone wears it.
- Squat test the risky combinations. Test the lightest color and the largest size, under bright light, over a contrasting underlayer. Record the lighting and sample number so you can repeat it on bulk goods.
- Wash it. Wash and dry as your care label will say, several times, then re-measure for shrinkage and check that the knees and seat recover instead of bagging.
- Stretch the seams. Flatlock and coverstitch seams should stretch with the fabric without popping stitches. Look closely at the gusset and the waistband join.
- Check the waistband. Does it roll down in a squat or a forward fold? Is there a pocket, and does it hold a phone without sagging?
- Sports bras: check that removable pads sit flat, don't shift after washing, and that straps and underband keep their tension.
- Logos and prints: stretch a printed logo hard; heat-transfer logos can crack. Rub a damp white cloth on dark colors to check for dye transfer.
Approve one sample as the reference and keep it with your supplier or agent. Bulk goods get checked against that unit, not against a photo.
Claims and chemicals: where activewear brands get caught
- "Antibacterial" is a pesticide claim. Under EPA rules, a fabric treated with, say, a silver finish can say it resists odor-causing bacteria on the fabric itself. Claims that it kills germs, is "antibacterial" or protects the wearer are public health claims, and they need EPA registration. Liability can reach whoever sells the product, not only the factory.
- BPA in polyester/spandex. Since 2022, the Center for Environmental Health has sent California Proposition 65 notices to many brands over BPA found in polyester/spandex sports bras, shirts, leggings and shorts. If you sell to California, ask your supplier for bisphenol test results on these fabrics, or plan for a warning.
- PFAS in water-repellent finishes. California bans PFAS in textiles above 100 ppm of total organic fluorine, falling to 50 ppm on January 1, 2027. If a jacket or short is "water-repellent", ask how.
- "UPF 50+" needs a test. In the US, sun-protection ratings are tested to AATCC 183 and labeled under ASTM D6603. Don't print a rating the fabric hasn't been tested for.
- The usual labels. Fiber content, country of origin, your company name and a permanent care label, as with any clothing. Our private label clothing guide covers those rules, including the CPSC flammability certificate.
Where to find activewear factories
For testing, 1688 lists stock leggings, sports bras and seamless sets you can buy in small quantities and relabel. For your own designs, Alibaba.com and the sportswear cluster around Quanzhou and Jinjiang in Fujian, home to several of China's big sports brands, are the usual starting points. When you shortlist, ask each factory whether it can run your fabric in a stock color or needs a custom dye. A custom color usually means a dye-lot minimum at the mill, and shade can drift between dye lots, so compare every reorder with your reference sample.
How fees add up for a first activewear batch
Say you order 400 sets of leggings and sports bras with your logo at a hypothetical $9.00 a set: $3,600 of product. PackQuay's sourcing fee for a transaction up to $5,000 is 10% ($360), and private label adds 2.5% ($90), so $4,050 before shipping. If a customer orders a set as two separate SKUs, pick and pack is $2.00 plus $1.00 for the second SKU on days with up to 19 orders, and less as daily volume rises. Free inspection covers 20% of each batch; measurement checks beyond that are $7 per person per hour. See inspection and pricing for details.
How PackQuay helps
We collect fabric specs and test reports from shortlisted factories, run your samples through the checks above, and keep the approved sample in our warehouse in Xinxiang, Henan, so each bulk batch is compared with it on arrival. Your sets are then packed in your branding and shipped on 30+ shipping lines. If you also sell swimwear or lingerie, they can ship from the same stock in one parcel. Message us on WhatsApp with the styles you have in mind.
FAQ
What fabric is best for activewear leggings?
Most premium leggings use nylon with spandex because it feels soft and stays opaque at a lower weight. Polyester with spandex dries faster, holds color well and takes sublimation prints, but usually needs a heavier fabric to pass a squat test.
What tests should I ask an activewear manufacturer for?
Ask for fiber content, fabric weight in GSM, stretch and recovery to ASTM D2594, wicking to AATCC 195 or 197, colorfastness to perspiration to AATCC 15 and pilling to ASTM D4970. Then do your own squat and wash tests on samples.
Can I call my activewear antibacterial?
Not without care. In the US, a claim that the fabric resists odor-causing bacteria on itself can fall under an EPA exemption, but claims that it kills germs or protects the wearer need EPA registration.
How do I make sure leggings are not see-through?
Get the fabric weight and knit in writing before sampling, then squat-test the lightest color and largest size under bright light over a contrasting underlayer. Repeat the same test on bulk goods before they ship.
Is there a minimum order for custom activewear?
Relabeling stock styles can start small. A custom fabric color usually brings a dye-lot minimum at the mill, so ask whether the factory can use a stock color for your first run.