COMPARISONS
This is a side-by-side. Eight criteria. Honest scoring on each.
We sell cotton activewear, so the bias is obvious. We are going to try to be fair about the places polyester actually wins, and there are a few. The point is not to declare cotton perfect. The point is to lay out the trade-offs and let you decide what matters for your training.
Criterion 1, breathability
Cotton wins. Cotton fibres allow air to move through the fabric. Heat releases from the body instead of pooling against the skin. The microclimate under cotton stays closer to ambient temperature. Polyester fibres are denser, more tightly knit in most activewear constructions, and chemically hydrophobic. Heat and moisture have a harder time releasing. High-end performance polyesters use specialised weaves to improve airflow. They help. They do not match the breathability of natural cotton, especially in still air.
Criterion 2, moisture absorption
Cotton wins on absorption. Polyester wins on speed. Cotton absorbs sweat into the fibre. The fabric can hold up to 25% of its weight in water before it starts to feel wet on the surface. Skin contact stays drier longer at low-to-moderate sweat rates. Polyester does not absorb. Sweat sits on the fabric surface and evaporates. At high sweat rates this evaporation can cool you faster, but at low rates the wet sensation against the skin starts immediately because there is nowhere for the moisture to go. Pilates, yoga, light strength training: cotton absorption wins. Sprint intervals in cold weather: polyester surface-evaporation has an edge.
Criterion 3, drying speed
Polyester wins. After your workout, polyester dries dramatically faster. Throw a polyester top in your gym bag and it will be dry by the time you get home. Throw a cotton top in and it will still be damp. This matters for travel, multi-session days, and any situation where you cannot wash and dry between wears. It matters less for daily training where the garment goes straight into the laundry.
Criterion 4, odour control
Cotton wins clearly. This is the gap most people notice in their own laundry. Polyester develops persistent odour faster, holds it longer, and does not always release it in the wash. Cotton does not develop the same biofilm and washes out cleanly. A 2014 study by Callewaert et al. in Applied and Environmental Microbiology found significantly higher concentrations of odour-producing bacteria on polyester garments after a single workout. The full explanation is in why polyester smells faster.
Criterion 5, skin feel and irritation
Cotton wins. Cotton is softer, gentler, and less likely to cause irritation against skin under heat, sweat, and friction. For sensitive-skin wearers and people with eczema or contact dermatitis, this is not a marginal difference. It is often the difference between trainable and unwearable. GOTS-certified cotton has the additional advantage of audited chemical processing. Most fabric-related skin reactions come from finishing chemicals, not the fibre itself, and polyester is rarely sold without a heavy load of finishes. The skin side of that is in why your sportswear makes you itch.
Criterion 6, microplastic release
Cotton wins. Polyester sheds microplastic fibres during every wear and every wash. These fibres end up in the air, in waterways, and in the food chain. Recycled polyester sheds at comparable rates to virgin polyester, which we cover in is recycled polyester actually sustainable. Cotton does not shed microplastics. Cotton does shed cellulose fibres, which biodegrade.
Criterion 7, stretch and recovery
Polyester wins on its own. Cotton wins with a small spandex blend. Pure cotton has minimal stretch. A 100% cotton sports legging would not work. It would bag out at the knees within an hour and lose its shape after one wash. Polyester blended with spandex stretches and recovers extremely well, which is why the activewear industry standardised on it. The fix on the cotton side is straightforward: blend in a small percentage of spandex. With 6 to 10% spandex, cotton-dominant activewear matches polyester on stretch and recovery for almost all training. It does not match polyester for ultra-compression performance gear, but most people are not training in that anyway. Why two leggings with the same percentage on the tag can feel completely different is in why two leggings with the same composition feel different.
Criterion 8, long-term durability
Cotton wins, with a caveat. Quality cotton ages well. The fibre softens, stays comfortable, and holds shape through hundreds of wash cycles. Cotton garments worn into their second decade are common. Polyester does not really degrade in the same visible way, but it changes. The fibre stiffens slightly, the colour fades, the elastic structure breaks down faster than the fibre itself. Most polyester activewear is functionally past its prime within two years of regular use. The caveat: low-quality cotton can pill, tear, or lose shape quickly. Construction quality and yarn grade matter more for cotton than they do for polyester. For LAINE HILL specifically we use long-staple GOTS-certified cotton, which is a meaningful step above commodity cotton on durability.
Final score, six to two
Cotton wins on breathability, odour, skin feel, microplastic release, and long-term durability. It wins on moisture absorption at low-to-moderate sweat rates. Polyester wins on drying speed and on stretch and recovery on its own. The drying-speed advantage is real but matters in narrow conditions: long outdoor cardio, travel, multi-session days. The stretch-and-recovery advantage disappears once you blend a small percentage of spandex into the cotton. For studio, gym, low-impact, and indoor training, cotton with 8% spandex outperforms polyester on every criterion that affects how the workout actually feels on the body. That is what we built. Not because cotton is fashionable. Because the data is clear once you stop trusting the marketing. The full reasoning is in for half a century we got it wrong.
LAINE HILL
Continue reading
- Best natural fabrics for activewear. Cotton, merino, tencel, bamboo, hemp, modal, linen, compared.
- What to wear for what, best fabrics by sport. The right fabric for yoga, strength, running, hot yoga, and more.
- Why polyester smells faster. The bacteria behind workout odour.
Cotton vs polyester, criterion by criterion
| Criterion | Cotton (with 8% spandex) | Polyester | Winner |
|---|---|---|---|
| Breathability | High, air moves through | Lower, denser knit | Cotton |
| Moisture absorption | High, absorbs into fibre | None, sits on surface | Cotton |
| Drying speed | Slower | Fast | Polyester |
| Odour control | Washes out clean | Persistent biofilm | Cotton |
| Skin feel | Soft, gentle | Coarser, more finishes | Cotton |
| Microplastic release | None (biodegrades) | Sheds every wash | Cotton |
| Stretch and recovery | Matches poly with 8% spandex | Excellent | Tie |
| Long-term durability | Ages well, softens | Stiffens, fades | Cotton |
Common questions
Is cotton or polyester better for the gym?
For most types of training, cotton wins on six out of eight criteria: breathability, moisture absorption, odour, skin feel, microplastic release, and long-term durability. Polyester wins on drying speed and on stretch and recovery. With a small percentage of spandex added to cotton, the stretch gap closes. The drying-speed gap is real but only matters in specific conditions like cold-weather outdoor cardio.
Why do most sportswear brands use polyester then?
Three reasons: it is cheap, it is consistent across batches, and it is durable in the manufacturing sense (does not shrink, holds dye, ships well). Those are operational reasons, not performance reasons for the wearer. The activewear industry standardised on polyester in the 1980s and 90s for cost and supply-chain reasons. The performance story was built around the choice that had already been made.
Doesn't polyester wick sweat better?
It moves sweat differently. Polyester is hydrophobic. It does not absorb sweat into the fibre, so the moisture moves along the surface and evaporates quickly. Cotton is hydrophilic. It absorbs sweat into the fibre and releases it through evaporation more slowly. For high-intensity outdoor cardio in cold weather, polyester's faster surface-level drying helps. For most other training, cotton's absorption keeps the skin drier in a different way.
When is polyester actually the right choice?
For long-distance outdoor running or cycling in cold or wet conditions, where drying speed matters most. For pool and aqua training, where chlorine resistance matters. For technical outdoor gear that does not sit against skin all day. For most studio, gym, and indoor training, cotton with a small spandex percentage outperforms polyester on the criteria that affect how the workout actually feels.