Natural Fiber Activewear FAQ: Everything You Need to Know
Natural fiber activewear is made from plant-derived or animal-derived fibers rather than petroleum-based synthetics such as polyester or nylon. The most common options used in activewear are TENCEL Lyocell, organic cotton, merino wool, and bamboo-derived viscose. Natural fibers generally do not contain PFAS or phthalates, do not shed synthetic microplastics, and are better suited to sensitive skin than most synthetic alternatives. Performance varies significantly by fiber type and activity intensity.
- Natural fibers used in activewear: TENCEL Lyocell, organic cotton, merino wool, bamboo viscose
- Do not contain PFAS or require fluoropolymer finishing coatings at fiber level
- Do not shed synthetic microplastics — shed cellulose or protein microfibers that biodegrade faster
- TENCEL Lyocell is certified non-toxic at fiber level by OEKO-TEX Standard 100 through Lenzing AG
- Best suited to yoga, pilates, barre, reformer training, and walking at low to moderate intensity
- Most natural fiber activewear contains 5–15% spandex for stretch — that component is synthetic
- Bamboo-derived activewear is typically bamboo viscose, not natural bamboo fiber, despite common labelling
What Are Natural Fibers in Activewear?
What is a natural fiber?
A natural fiber is one derived from a plant, animal, or mineral source rather than synthesised from petroleum or other chemical precursors. Common examples include cotton (plant), wool (animal), and silk (animal). Plant-derived regenerated fibers such as TENCEL Lyocell occupy a middle position: they begin as natural wood cellulose but are transformed through an industrial process before becoming a wearable fiber. These are typically called plant-derived or regenerated natural fibers to distinguish them from both fully natural and fully synthetic materials.
What is the healthiest fabric to wear?
For skin contact during exercise, plant-derived and natural fibers that carry independent third-party certification are the best-supported choice on current evidence. TENCEL Lyocell holds OEKO-TEX Standard 100 certification at the fiber level through Lenzing AG, confirming it has been tested for more than 1,000 harmful substances including PFAS, phthalates, formaldehyde, and heavy metals. Organic cotton and certified merino wool occupy a similar position. The key qualifier is that fiber origin alone is not sufficient: dyeing and finishing processes applied after fiber production can introduce harmful substances regardless of fiber type. Full garment certification such as OEKO-TEX Standard 100 at the finished-product level provides the most complete confirmation. Bellissima holds fiber-level certification through Lenzing AG. Finished-product certification is in progress.
What natural fibers are used in activewear?
The natural and plant-derived fibers most commonly used in activewear are TENCEL Lyocell, organic cotton, merino wool, and bamboo-derived fibers. Each has meaningfully different performance properties. TENCEL Lyocell and merino wool manage moisture actively. Cotton absorbs well but dries slowly and becomes heavy when wet. Bamboo viscose is soft but the chemical processing required to convert bamboo into a wearable fiber is significant, which complicates its natural fiber claim. Bellissima's natural fiber activewear collection is built around TENCEL Lyocell for this reason.
Is bamboo activewear actually natural?
This is contested. Bamboo is a natural plant, but converting it into a wearable fiber typically requires dissolving the plant material in chemical solvents, producing a fiber structurally equivalent to viscose or rayon. The US Federal Trade Commission took action against brands for labelling bamboo-derived viscose as bamboo fabric, finding it misleading (FTC, 2013). The resulting fiber is more accurately described as bamboo viscose or bamboo rayon. TENCEL Lyocell uses a closed-loop solvent recovery process that recaptures more than 99% of its solvent and holds EU Ecolabel certification that bamboo viscose typically does not.
Is merino wool or TENCEL better for activewear?
Both are strong natural fiber options but with different strengths. Merino wool is an excellent thermoregulator and performs well across a wide temperature range. It manages odour exceptionally well and is suited to multi-day wear in outdoor activity. It is more expensive per kilogram of fiber and can feel slightly itchy on sensitive skin when damp. TENCEL Lyocell has a smoother fiber surface and is better suited to skin-contact activewear worn directly against the body during structured indoor exercise such as yoga, pilates, and reformer training. For outdoor endurance activity in variable temperatures, merino wool has advantages. For studio fitness and everyday active wear, TENCEL is the stronger choice for most people.
Is organic cotton good for working out?
Organic cotton is better than conventional cotton for skin safety, grown without synthetic pesticides and processed without harsh chemical finishing agents. As a workout fabric, it has a functional limitation: cotton absorbs moisture but releases it slowly. During moderate to intense exercise, cotton becomes heavy and stays damp against skin. TENCEL Lyocell absorbs moisture at a similar rate but releases it more efficiently, producing a drier feel during movement. For low-intensity activity or casual wear, organic cotton works well. For regular structured exercise, it is not the strongest performing natural fiber option.
Health and Safety
Why do people choose natural fiber activewear?
The primary reasons are skin safety and chemical exposure reduction. Conventional synthetic activewear, particularly polyester and nylon, is often manufactured with or treated by PFAS, phthalates, and chemical finishes that have raised health concerns in independent research. Peaslee et al. (2020), in Environmental Science and Technology Letters, identified PFAS in a range of athletic garments. Vandenberg et al. (2012), in Endocrine Reviews, identified phthalates and PFAS among the chemical classes most associated with endocrine disruption in consumer products. Natural and plant-derived fibers generally do not require these finishing chemicals to perform.
What activewear is free from PFAS?
Activewear made from natural or plant-derived fibers not treated with DWR fluoropolymer coatings is generally PFAS-free at fiber level. TENCEL Lyocell, organic cotton, and merino wool are the most commonly available options. Fiber origin alone does not guarantee PFAS absence in the finished garment: dyeing and finishing can introduce PFAS regardless of fiber type. OEKO-TEX Standard 100 certification at the finished-garment level provides the most reliable confirmation. Bellissima's Sempre collection uses TENCEL Lyocell certified OEKO-TEX Standard 100 at fiber level through Lenzing AG.
Do natural fibers contain PFAS?
Natural fibers in their unprocessed state do not contain PFAS. Contamination enters during dyeing, finishing, and treatment processes applied after the fiber is made. A brand using natural fibers can still produce a garment with PFAS-containing dyes or finishes unless the full supply chain is certified. Fiber-level natural status is necessary but not sufficient for a complete health claim.
Do natural fiber activewear garments shed microplastics?
Natural and plant-derived fibers do not shed synthetic microplastics. Particles shed during washing are cellulose or protein-based microfibers that biodegrade significantly faster than synthetic polymer fragments. De Falco et al. (2020), in Scientific Reports, found cellulose microfibers biodegraded substantially in aquatic environments where polyester microfibers showed little change. One honest clarification: most natural fiber activewear contains a percentage of synthetic spandex or elastane for stretch. That component does shed microplastics. Bellissima's Sempre collection is 92% TENCEL Lyocell and 8% spandex. We do not claim the garments are microplastic-free. The spandex content makes that claim inaccurate.
Are natural fibers better for sensitive skin?
For most people with sensitive or reactive skin, natural and plant-derived fibers cause fewer problems than synthetic alternatives. The primary reasons are surface texture and chemical exposure. Hofer et al. (2020), in Dermatology and Therapy, found that fiber surface roughness and chemical residues from finishing processes are two of the main drivers of textile-induced skin irritation. TENCEL Lyocell fibers are microscopically smooth and produced without the harsh finishing agents common in polyester production. Individual sensitivity varies, but the research basis for natural fiber preference in skin-sensitive individuals is substantive.
Performance
How do natural fibers perform in activewear compared to synthetics?
For yoga, pilates, barre, reformer training, and walking, TENCEL Lyocell moisture management is well matched to the activity. Polyester's advantage at high intensity is that it is hydrophobic: sweat sits on the surface and evaporates quickly rather than being absorbed. This produces fast drying at very high sweat rates. TENCEL Lyocell is hydrophilic and absorbs moisture into the fiber, producing a drier feel against skin during moderate output but potentially saturating faster at extreme intensity. For sustained high-intensity output such as HIIT or distance running, synthetic fabrics have a measurable functional advantage. Bellissima states this distinction directly rather than overclaiming.
Do natural fibers resist odour?
Yes, generally better than synthetic alternatives. Polyester is hydrophobic and sweat sits on the surface, creating conditions that encourage bacterial growth. The permanent odour that builds up in synthetic activewear over time is primarily caused by this. TENCEL Lyocell and merino wool manage moisture in ways that reduce the conditions bacteria need to proliferate. Lenzing's technical documentation shows bacterial growth rates on TENCEL Lyocell substantially lower than on polyester under equivalent conditions. This is a function of moisture management, not a chemical antimicrobial finish.
Do natural fiber leggings hold their shape?
Natural fibers alone do not provide the compression and shape retention activewear requires. Most natural fiber activewear uses 5 to 15% spandex or elastane for structural hold. The TENCEL Lyocell content provides skin-contact comfort, moisture management, and breathability. The spandex provides compression, shape recovery, and fit security. Bellissima's Sempre collection uses 92% TENCEL / 8% spandex, keeping spandex at the functional minimum while maximising natural fiber content.
Are natural fiber leggings squat-proof?
Squat-proof performance depends on fabric weight and construction, not fiber category alone. A lightweight natural fiber fabric will not be squat-proof. Bellissima's Sempre Leggings and Sempre Shorts use a 240 GSM interlock weft knit construction that is fully opaque under stretch. The opacity comes from fabric weight and construction. Any brand claiming squat-proof performance in natural fiber activewear should be evaluated on fabric weight and construction, not fiber category alone.
Sustainability
Are natural fibers more sustainable than synthetics?
On most environmental measures, yes, with nuance. Polyester is derived from petroleum, is not biodegradable, and carries a higher carbon footprint per kilogram of fiber. Shen and Patel (2010), in Lenzinger Berichte, calculated polyester's lifecycle carbon footprint at approximately 9.5 kg CO2 equivalent per kilogram. Lenzing's 2023 Sustainability Report places TENCEL Lyocell's fiber-level footprint at 1.7 kg CO2 equivalent per kilogram. Organic cotton uses significantly less synthetic pesticide than conventional cotton but is water-intensive. The most accurate sustainability comparison accounts for fiber production, dyeing, transport, garment longevity, and end-of-life disposal together, not fiber origin alone.
Are natural fiber activewear garments biodegradable?
The natural fiber content is biodegradable. TENCEL Lyocell fiber is certified biodegradable by TUV Austria. Cotton and wool biodegrade in most conditions. Finished activewear garments typically include spandex, synthetic thread, and elastic, none of which biodegrade at the same rate as the natural fiber content. Bellissima's Sempre garments contain 8% spandex, which is not biodegradable. Honest sustainability framing acknowledges this rather than claiming full biodegradability based on fiber content alone.
Bellissima and Natural Fibers
What natural fiber does Bellissima use, and why?
Bellissima uses TENCEL Lyocell, produced by Lenzing AG, as the primary fiber in the Sempre collection. The composition is 92% TENCEL Lyocell and 8% spandex across all four products. TENCEL was chosen because it combines the skin safety profile of a plant-derived fiber with moisture management suited to structured exercise, a certified and traceable supply chain, and OEKO-TEX Standard 100 fiber-level certification. No other natural or plant-derived fiber available at scale delivers the same combination of properties for activewear use. Browse Bellissima's full natural fiber activewear range, or explore by activity in the pilates clothes and yoga clothes collections.
What is the difference between Bellissima and conventional activewear brands?
Most activewear is made from polyester, nylon, or polyester-spandex blends, all petroleum-derived synthetic fabrics. Bellissima's Sempre collection is 92% TENCEL Lyocell, a plant-derived regenerated fiber that does not contain PFAS, does not require chemical antimicrobial finishes, and holds OEKO-TEX Standard 100 certification at fiber level. The practical differences include a softer hand feel against skin, better moisture absorption behaviour at low to moderate intensity, and the absence of permanent synthetic odour that builds up in polyester activewear over time. The honest trade-off is that TENCEL Lyocell is not the fastest-drying fabric at very high intensity output. Bellissima states this clearly across all content. See the full non-toxic activewear collection for Bellissima's complete range.
Sources
De Falco, F., et al. (2020). Microfiber Release to Water, Via Laundering, and to Air, via Everyday Use: A Comparison between Polyester Clothing with Conventional and Sustainable Microfibers. Scientific Reports.
Federal Trade Commission (2013). FTC Actions Against Bamboo Fiber Labelling Claims. US Federal Trade Commission.
Hofer, D., et al. (2020). Skin Sensitization and Textile Contact Dermatitis. Dermatology and Therapy.
Lenzing AG (2023). Annual and Sustainability Report. Lenzing Group.
Peaslee, G.F., et al. (2020). PFAS in Clothing. Environmental Science and Technology Letters.
Shen, L., and Patel, M.K. (2010). Life Cycle Assessment of Man-Made Cellulose Fibres. Lenzinger Berichte.
Vandenberg, L.N., et al. (2012). Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and Nonmonotonic Dose Responses. Endocrine Reviews.