Under Armour was built on a simple premise: synthetic performance fabric outperforms natural fiber for athletic use. The brand's identity is inseparable from its fabric technology. HeatGear, CoolGear, and its various moisture-management systems are the product. That makes Under Armour a useful case study in what performance chemistry in activewear actually involves.
For buyers evaluating non-toxic workout clothes, performance brands like Under Armour are exactly where the commitment-versus-certification distinction becomes most consequential.
What Under Armour's Performance Fabrics Are Made Of
Under Armour's core performance fabrics are synthetic, primarily polyester and nylon blends engineered for specific functional outcomes. The brand's moisture-management systems work by pulling sweat away from the skin and distributing it across the fabric surface for faster evaporation. This function is achieved through a combination of fiber construction and chemical finishing.
The chemical finishing component is the relevant part of this conversation. Moisture-wicking treatments, anti-odor applications, and the various performance finishes that give Under Armour fabrics their specific hand feel and functional properties involve chemistry that is applied to the fabric surface during manufacturing. What that chemistry consists of is not routinely disclosed on product labels. The full range of these finishing categories is covered in the research on toxic chemicals in workout clothes.
What the Certification Record Shows
As of the most recent publicly available information, Under Armour products do not uniformly carry OEKO-TEX Standard 100 certification on finished garments. Under Armour publishes a Restricted Substances List as part of its compliance framework, which sets limits on certain chemicals in materials sourced from suppliers. The brand has made commitments to responsible chemical management through its sustainability reporting.
A Restricted Substances List is a supplier-facing compliance document. It establishes what the brand requires of its supply chain. It is not independent testing of the finished garment at the product level. The distinction matters because compliance requirements and verified outcomes are different stages in the same process, and the publicly available record confirms the former without providing the latter for most Under Armour products. For context on how this gap has materialized at the industry's most scrutinized brand, whether Lululemon is non-toxic in 2026 and the PFAS specifics in whether Lululemon contains PFAS are directly relevant.
Performance Chemistry and Skin Contact
Under Armour's products are designed for extended wear during exercise, which means sustained skin contact under conditions of heat and perspiration. Research published in Environmental Science and Technology has documented that synthetic textiles release chemical compounds during wear, with transfer rates increasing under conditions of heat and moisture. Activewear worn during exercise is precisely the context where this transfer is most significant.
This does not mean Under Armour products contain PFAS at harmful levels. It means the performance chemistry that defines the brand's value proposition involves a set of questions about what is applied to the fabric and whether the finished product has been independently tested for the presence of regulated substances.
The Performance vs. Safety Trade-off Frame
There is a common assumption in the activewear category that performance and safety exist in tension: that fabrics engineered for athletic performance necessarily involve more chemical complexity than natural alternatives. This assumption is worth examining.
TENCEL Lyocell achieves its moisture management through the physical structure of the fiber itself. The hygroscopic properties of the fiber, its ability to absorb and release moisture within the fiber structure rather than on the surface, produce functional outcomes without applied finishing chemistry. Research by Kaplan et al. (2014) published in Fibers and Polymers documented TENCEL Lyocell's thermal comfort and moisture management properties in active wear contexts, confirming that the functional performance comes from fiber architecture rather than chemical treatment.
The Sempre Leggings are made from 92% TENCEL Lyocell and 8% spandex. No surface treatments. The performance properties are structural, not chemical. For a broader look at how large sportswear brands approach this same question, the Adidas PFAS analysis and the non-toxic activewear buying guide provide additional context for the full evaluation.
The Honest Assessment
Under Armour makes genuinely high-performing activewear built around a coherent and well-executed fabric technology strategy. The brand delivers on its performance promises. The gap in the publicly available record is finished product independent certification that confirms what is and is not present in those performance fabrics at a chemical level.
If maximum athletic performance is your primary criterion, Under Armour is a strong choice and the brand delivers what it promises. If you also want to know that the performance chemistry in your activewear has been independently verified at the finished product level, the public record does not provide that confirmation for most Under Armour products.
Sources
- Kaplan, S., et al. (2014). Thermal comfort of lyocell and other fibers in active wear. Fibers and Polymers, 15(6).
- Kotthoff, M., et al. (2015). Perfluoroalkyl and polyfluoroalkyl substances in consumer products. Environmental Science and Pollution Research.
- Under Armour. (2024). Restricted Substances List and Sustainability Commitments. underarmour.com.
- OEKO-TEX Association. (2024). OEKO-TEX Standard 100 Public Certification Database. oeko-tex.com.
- Lenzing AG. (2024). TENCEL Lyocell Fiber Certification and Production. lenzing.com.
