Activewear Fabric Specs 101: A Brand's Technical Guide From GSM to Recovery
If you want consistent fit, stable sizing, reliable bulk production, and durable performance, you don't need"fabric feelings."
You need a measurable, verifiable, repeatable Fabric Specification.In custom activewear development, most rework and returns trace back to one root cause: the fabric was never standardized by specs. Words like "soft,” "high-stretch," "squat-proof," and "premium" aren't wrong—but they're not executable standards. They're hard for factories to reproduce consistently and hard for brands to approve objectively.This guide converts subjective descriptions into factory-ready technical language and a brand-side acceptance framework, applicable to Sports Bras, Leggings, Yoga Sets, Tops, Skirts, Jackets, Hoodies, and more.
What Are Activewear Fabric Specs?
In activewear, fabric specs turn "feel" into "standards"—so brands can choose the right fabric, develop the right sample, and control bulk consistency.Fabric specs are a set of measurable parameters that define how a fabric should behave in real wear and bulk production, including:
• Weight & coverage (GSM, thickness, opacity)
• Elasticity & stability (Stretch, Recovery)
• Coverage & support (Opacity / Squat-proof, Support)
• Durability & appearance (Pilling, Abrasion, Seam Safety)
• Color performance & consistency (Colorfastness, Shade Consistency)
• Shrinkage & bulk risk control (Shrinkage, Lot Control)
• Handfeel & surface style (Handfeel, Finish)
The 12 Core Fabric Specs Every Brand Should Define
You don't need to test everything on day one, but you should always define target range + tolerance + verification method.
Spec 1: Composition
• Why it matters: handfeel, durability, dye behavior, cost, and certification feasibility
• How to specify: e.g., Nylon 80% / Spandex 20% (with allowed deviation)
• Common mistake: saying "nylon spandex" without the ratio—support and recovery can vary drastically
Spec 2: Fabric Structure
• Why it matters: stretch behavior, opacity, stability, and pilling tendency
• How to specify: Interlock / Jersey / Rib / Double-knit / Seamless knit
• Common mistake: same composition, different structure—looks similar but performs completely differently
Spec 3: GSM (Fabric Weight)
• Why it matters: coverage, support, drape, cost, and opacity
• How to specify: use a range, not a single number (e.g., 250–270 GSM)
• Common mistake: sample swatch is 260 GSM, bulk becomes 230 or 290 after dye/finish → fit and handfeel shift
Spec 4: Width
• Why it matters: affects yield/cost and directional stability
• How to specify: width range + tolerance
• Common mistake: width fluctuations change fabric consumption and the "fit feel"across lots
Spec 5: Stretch %
• Why it matters: mobility, comfort, and sizing tolerance
• How to specify: warp/weft stretch + test condition (load and extension)
• Common mistake: only asking for "4-way stretch"—that term covers huge variations
Spec 6: Recovery %
• Why it matters: the key indicator of premium performance; poor recovery causes baggy knees, sagging seats, rolling waistbands
• How to specify: recommend recovery at 1 min + 30 min
• Common mistake: focusing only on "high stretch," not "high recovery"
Spec 7: Opacity / Squat-proof
• Why it matters: the #1 complaint driver for leggings and light colors
• How to specify: define stretch ratio (e.g., 1.3×) + lighting condition + pass criteria
• Common mistake: treating "squat-proof"as a slogan instead of a test condition
Spec 8: Pilling Resistance
• Why it matters: perceived quality + return rate (inner thigh is the danger zone)
• How to specify: target rating after defined cycles
• Common mistake: writing "anti-pilling"without method or acceptance standard
Spec 9: Abrasion Resistance
• Why it matters: longevity at inner thigh/seat areas
• How to specify: cycles-to-failure or rating target
• Common mistake: confusing abrasion wear (fuzz/whitening/thinning) with “random quality instability”
Spec 10: Colorfastness (Sweat / Rub / Wash)
• Why it matters: staining, crocking, fading complaints
• How to specify: set targets for perspiration (acid/alkali), dry/wet rubbing, and washing
• Common mistake: dark colors often fail wet rubbing; light colors are sensitive to sweat
Spec 11: Shrinkage
• Why it matters: sizing stability, especially for hoodies/jackets/cotton blends
• How to specify: max shrinkage % in warp/weft + wash condition
• Common mistake: assuming "sample doesn't shrink = bulk won't shrink"
Spec 12: Finish & Handfeel
• Why it matters: brand positioning and perceived premium level
• How to specify: finish type (matte/brushed/peach/cooling/wicking) + sealed reference swatch
• Common mistake: "buttery" interpreted as "shinier/thinner" → wrong aesthetic and durability risk
Practical Spec Ranges by Product Type (Starting Points)
These are typical working ranges. Final targets depend on positioning (studio vs training), silhouette, and price tier.
• Common composition: Nylon/Spandex or Polyester/Spandex
• Typical GSM: 220–320
• Key focus: recovery (prevents ride-up), stability (reduces dig-in), sweat colorfastness
• Common composition: Nylon 75–85% + Spandex 15–25%
• Typical GSM:
• Studio/Yoga: 220–280
• Training/Compression: 250–320
• Key focus: opacity under stretch, inner-thigh pilling, knee recovery
• Typical GSM: 160–220
• Key focus: neckline/edge stability, lightweight but not sheer, wash shape retention
• The key isn't "each piece looks good,"but "both pieces match"
• Recommendation: same lot/same finishing + shade band management to prevent mismatch
• Typical GSM: 280–420 (varies by terry vs fleece)
• Key focus: shrinkage, twisting/skewing, surface fuzz, wash stability
Stretch vs Recovery: The Real Divider of Premium Activewear
Many brands only ask, "How stretchy is it?"
But the spec that defines premium quality is often Recovery.
• Stretch answers: "Can it move?"
• Recovery answers: "Will it return and stay new-looking after repeated wear?"
Typical symptoms of poor recovery:
• waistband sliding down (especially high-waist leggings)
• baggy knees and sagging seat
• fit drift across time and washes
Squat-proof Isn't a Claim—It's a Standard
"Squat-proof" must be defined as a repeatable test condition, not marketing language.
At minimum, define:
1. Stretch ratio (e.g., 1.3×)
2. Lighting condition (light box or fixed lighting standard)
3. Pass criteria (visual rating or defined threshold)
This matters because opacity changes by size and stretch. Once standardized, you can determine whether the issue is the fabric, the fit, or the test condition.
Durability Specs: The “Return Rate Trio”
To reduce returns, durability specs matter more than "nice handfeel."
Pilling
• Risk zones: inner thigh, seat, underarm
• Drivers: fiber length, yarn strength, brushed finishes
• Brand recommendation: set rating + cycles, not just "anti-pilling"
Abrasion
• Risk zones: seat rubbing, inner-thigh friction
• Drivers: structure, yarn, finishing
• Recommendation: higher targets for leggings/pants/skirts inner short
Seam Safety
• Stretchy fabric doesn't guarantee strong seams
• Must match thread, stitch density, stitch type, and construction to the stretch level
Colorfastness: Dark Colors = Rubbing Risk, Light Colors = Sweat Risk, Sets = Shade Risk
Color issues are typically three different risks:
1. Crocking (rub-off): most common in dark colors (black/red/purple)
2. Perspiration staining: more visible on light colors (white/pink/light gray)
3. Shade mismatch: the biggest complaint source for sets
Brand best practice: write colorfastness as measurable targets and keep a shade band for repeat orders.
How to Specify "Soft"Without Miscommunication
"Soft" can mean completely different finishes:
• Brushed (warmer, fuzzier, but can pill)
• Peach (fine, matte, premium touch)
• Slick (smooth, can look shiny or thin)
• Matte (premium look, higher quality requirement)
• Cooling (requires specific yarn/finish)
Correct approach:
Use finish naming + sealed reference swatch + acceptable deviation range—so bulk stays aligned.
Fabric Spec Sheet Template (Brand-Ready)
Use this format inside your tech pack or sourcing document.
Fabric Spec Sheet
• Fabric Name / Code
• Supplier / Mill
• Intended Product (Leggings / Sports Bra / Set / Top / Skirt)
• Composition
• Structure
• Finish (Matte / Brushed / Peach / Cooling / Wicking)
• GSM target range + tolerance
• Width target range + tolerance
• Stretch (Warp/Weft) target + test condition
• Recovery (1 min / 30 min) target + test condition
• Opacity / Squat-proof condition:
• Stretch ratio
• Lighting
• Pass criteria
• Pilling target
• Abrasion target
• Colorfastness targets:
• Perspiration
• Rubbing (Dry/Wet)
• Washing
• Shrinkage (Warp/Weft) max
• Reference swatch code
• Certifications (if required): GRS / GOTS / OEKO-TEX
• Bulk approval: Lab dip / Strike-off / Shade band
Bulk Acceptance Checklist (Brand QC)
In bulk stage, at minimum:
• confirm same mill / same lot / same finishing (especially for sets)
• re-check GSM & width on finished bulk fabric (not greige)
• re-test stretch + recovery (not only sample swatches)
• run opacity test at defined stretch ratio + lighting
• verify rubbing and sweat risks (dark vs light focus)
• check shrinkage and skewing for cotton/fleece/blends
• keep sealed reference swatches for repeat orders
Final Note: Turning Fabric Specs Into Bulk-Ready Reality at Bloomto
At the end of the day, fabric specs only create value when they can be executed consistently—across sampling, bulk production, and repeat orders. As a custom yoga wear & activewear manufacturer, Bloomto Sportswear Manufacturer helps established brands translate "premium feel" into lab-verifiable standards: stretch & recovery, colorfastness, pilling resistance, moisture-wicking performance, and more.
What makes the difference is the system behind the fabric. Bloomto's fabric R&D is driven by user experience and market demand, supported by an in-house R&D team and comprehensive testing—so you can approve performance with data, not assumptions. We also support custom development with a steady pipeline of new fabrics each year, including proven in-house innovations (such as our double-brushed stretch fabric option) and certified sustainable directions using recycled yarns and responsible dyeing/finishing practices.
f you're building a collection for scale, the fastest way to reduce returns and rework is to start with a clear Fabric Spec Sheet—and work with a manufacturer that can validate it. Explore our Fabric R&D Capabilities and request fabric samples, or visit the Bloomto homepage to see our full custom activewear solutions.
FAQ
Q1. What GSM is good for leggings?
Many studio/yoga leggings fall around 220–280 GSM, while training/compression styles often use 250–320 GSM. Final GSM depends on opacity and support targets.
q2.Why do leggings get baggy knees even with high spandex?
The problem is usually recovery, not stretch. Poor recovery means the fabric doesn’t return to shape after repeated wear.
q3.How do brands define squat-proof correctly?
Define test conditions: stretch ratio, lighting method, and pass/fail criteria. Squat-proof should be documented and verifiable.
Q4.Nylon vs Polyester—how should brands choose?
Nylon often feels smoother and more premium; polyester can work great for prints and durability. Either way, you need the same spec framework (GSM, recovery, opacity, pilling, colorfastness).
Q5.What's the most important fabric spec for premium activewear?
Recovery. It protects fit stability, reduces returns, and keeps garments looking new longer.
