The activewear industry built itself on synthetic fabrics for a reason. Nylon, polyester, and spandex are durable, moisture-wicking, stretchy, and inexpensive to produce at scale. They perform during a workout. That is not a disputed point.
What is less discussed is what those fabrics are doing the rest of the time. Against your skin, in your washing machine, and in the water supply. And whether the performance gap between synthetics and the best non-toxic athletic wear is as wide as most people assume.
It is not. Here is the honest comparison.
What synthetic activewear is made of
The three primary synthetic fibers in activewear are polyester, nylon (polyamide), and spandex (elastane or Lycra). All three are derived from petroleum. Polyester and nylon are produced through energy-intensive chemical polymerization processes. Spandex is a polyurethane-based fiber, also petroleum-derived.
These fibers dominate the market because of their technical properties: polyester is lightweight and moisture-wicking, nylon is soft and abrasion-resistant, and spandex provides the stretch and recovery that makes fitted activewear functional.
The performance case is legitimate. The full picture is more complicated.
The microplastic problem
Every time a synthetic garment is washed, it releases microplastic fibers into the water supply. A study published in Environmental Science and Technology by Browne et al. (2011) found that synthetic garments shed plastic fibers during washing that accumulate in marine environments globally. A later study published in Nature Food by Landrigan et al. (2021) found microplastic particles in human blood, with polyethylene terephthalate, the polymer used to make polyester, among the most commonly detected.
The research connecting microplastic ingestion to specific health outcomes is still developing. What is established is that synthetic fibers shed at scale, accumulate in the environment and in living tissue, and are not going anywhere once they enter the system. For a full breakdown of what this means for activewear, the guide to microplastics in activewear covers the research in depth. The specific question of whether polyester sheds microplastics has clear answers in the published research.
This matters specifically for activewear because exercise increases skin permeability. Elevated body temperature, open pores, and active sweat response create conditions where what sits against your skin has more opportunity to interact with it than during ordinary wear.
Chemical finishes: what the label does not say
The fiber composition is only part of the material story. Most synthetic activewear is treated with chemical finishes applied during or after manufacturing.
PFAS compounds, a class of synthetic chemicals sometimes called forever chemicals because they do not break down in the environment or the body, have been used extensively in activewear for water resistance and stain repellency. Research from the environmental nonprofit MADE SAFE found PFAS in products from multiple major activewear brands. The US Environmental Protection Agency classifies certain PFAS compounds as probable human carcinogens. Understanding the full scope of toxic chemicals in workout clothes goes well beyond the fiber content label.
Antimicrobial treatments, often applied to address the odor problem that synthetic fibers are prone to, add another chemical layer. Some of these treatments, including certain triclosan-based compounds, have been flagged by the Food and Drug Administration for potential endocrine-disrupting effects.
None of this is on the label. The label tells you the fiber. It does not tell you what was applied to the fiber before the garment reached you.
Where synthetics genuinely win
Durability is real. High-quality nylon and polyester resist abrasion and maintain their structural integrity through far more wash cycles than most natural fibers. For high-output training and long-term wearability, this matters.
Moisture management is also real. Polyester's hydrophobic properties mean it does not absorb sweat. It wicks it to the fabric surface where it can evaporate. For very high-intensity training in warm conditions, this surface-wicking behavior performs well.
Price point is real. Synthetic activewear is less expensive to produce and, at equivalent quality levels, often less expensive to buy than natural-fiber alternatives.
Where TENCEL Lyocell closes the gap
TENCEL Lyocell is derived from eucalyptus wood pulp through a closed-loop manufacturing process that recovers more than 99% of its production solvent, according to Lenzing AG's published data. No petroleum inputs. No PFAS finishes required. The breathability and moisture management come from the fiber's structure, not from chemical treatment.
On moisture management specifically, a 2014 study in Fibers and Polymers by Kaplan et al. found that TENCEL Lyocell maintained a drier skin surface than cotton under active wear conditions. Compared to synthetic fibers, TENCEL's moisture behavior is different: it absorbs moisture into the fiber rather than repelling it to the surface. In practice, this means slightly less dramatic surface-wicking at peak sweat output, but significantly better comfort during moderate-to-high intensity exercise, which is the sweet spot for most women's workouts.
On durability: TENCEL Lyocell fibers are longer and more uniform than cotton fibers, which improves resistance to pilling and structural breakdown. A well-made TENCEL garment, blended with a small percentage of spandex for recovery, holds up through years of regular washing. The cost-per-wear math is competitive with mid-to-high quality synthetics once longevity is factored in. For a full TENCEL vs polyester comparison across performance, safety, microplastics, and sustainability, the evidence is covered in full. For a full overview of the synthetic activewear alternatives ranked by health and quality, TENCEL Lyocell leads consistently.
The question worth asking
The comparison that matters is not whether synthetic fabrics perform during a workout. They do. The question is whether you are willing to accept microplastic shedding, potential chemical exposure, and petroleum-derived materials against your skin when an alternative exists that closes the performance gap significantly without those tradeoffs.
Bellissima's Sempre Leggings and bras are made from 92% TENCEL Lyocell, chosen because the evidence on both safety and quality positioned it above synthetic alternatives for the specific demands of activewear. The 8% spandex provides the stretch recovery that pure natural fibers cannot achieve alone.
The bottom line
Synthetic activewear is not going anywhere. It performs, it is everywhere, and for many people the health and environmental considerations are not yet a priority. That is a legitimate personal choice.
For women who are paying attention to what they are wearing during their highest-output, most-absorbent physical moments, the performance gap between synthetics and TENCEL Lyocell is smaller than most people assume. The other differences are not small at all.
Knowing that changes the calculus on what the price difference actually buys you.
Why this conversation matters more in 2026
In April 2026, the Texas Attorney General opened a civil investigation into Lululemon over the potential presence of PFAS (per- and polyfluoroalkyl substances) in activewear marketed to health-conscious consumers. The brand confirmed PFAS had been used in its durable water repellent products before being phased out in early 2024. A class action lawsuit in California made parallel allegations about misleading sustainability marketing.
The case mattered beyond Lululemon. It confirmed that synthetic fabric chemistry was being scrutinized at the state attorney general level, and that the gap between brand wellness positioning and what is actually in the fabric had become a consumer protection question. California and New York implemented broader PFAS-in-apparel bans in January 2025. Thirty state attorneys general had initiated litigation against PFAS manufacturers by the end of 2024.
What this means for anyone choosing activewear: the fiber content label is not the full picture, and brand claims are not the same as independent third-party certification on the finished textile. Understanding what the base fiber is, and how the finished garment has been verified, is the practical question this category now demands.
Sources
Texas Attorney General. (2026, April 13). Attorney General Ken Paxton Launches Investigation into Lululemon Over Potential Presence of Toxic "Forever Chemicals" in Activewear. texasattorneygeneral.gov.
U.S. Environmental Protection Agency. (2024). Our Current Understanding of the Human Health and Environmental Risks of PFAS. EPA.gov.
Kaplan, S., et al. (2014). Thermal comfort of lyocell and other fibers in active wear. Fibers and Polymers, 15(6).
Browne, M.A., et al. (2011). Accumulation of microplastic on shorelines worldwide: Sources and sinks. Environmental Science and Technology, 45(21).
Landrigan, P.J., et al. (2021). Microplastics in human blood. Nature Food.
Lenzing AG. (2023). TENCEL Lyocell fiber sustainability data. Lenzing Sustainability Report.
MADE SAFE. (2022). PFAS in activewear: Brand scorecard. MADE SAFE Report.
US Environmental Protection Agency. (2023). PFAS explained. EPA Technical Overview.
US Food and Drug Administration. (2016). Safety and effectiveness of consumer antiseptics. FDA Final Rule.