Fabric composition is the most important factor in activewear performance, yet it's often overlooked by shoppers who focus primarily on brand, style, or price. Understanding what different materials do—and don't do—empowers you to make informed choices that enhance your workouts and maximise value. This deep dive into activewear fabrics explains the science behind performance materials.
The Fundamentals of Fabric Performance
All fabrics manage four key factors during exercise: moisture, temperature, stretch, and durability. Different materials excel in different areas, and the best choice depends on your specific activities and preferences.
Moisture Management
When you exercise, your body produces sweat to cool itself. What happens to that sweat depends entirely on your clothing. Absorbent fabrics soak up moisture and hold it, becoming heavy and uncomfortable. Moisture-wicking fabrics use capillary action to pull sweat away from your skin to the fabric's outer surface, where it can evaporate.
Thermoregulation
Your clothing affects how efficiently your body maintains optimal temperature. Some fabrics insulate, trapping body heat—useful in cold conditions but problematic when exercising in heat. Others facilitate heat transfer to the environment, keeping you cooler during intense activity.
Stretch and Recovery
Athletic movements require flexibility. Fabrics with good stretch accommodate full range of motion, while those with good recovery return to their original shape rather than bagging out over time.
Fabrics described as "4-way stretch" extend both horizontally and vertically. This provides superior movement freedom compared to 2-way stretch fabrics that only stretch in one direction.
Cotton: The Traditional Choice
Cotton has been clothing humanity for thousands of years, and its popularity in casual wear is well-deserved. However, its properties make it less than ideal for many exercise applications.
How Cotton Performs
Cotton fibres are highly absorbent—they can hold up to 27 times their weight in water. This means cotton readily soaks up sweat, becoming heavy and staying wet against your skin for extended periods. While the initial moisture absorption can feel cooling, the extended wetness often leads to chafing and discomfort during longer workouts.
Cotton dries slowly because moisture binds to the fibres rather than sitting on the surface where airflow can evaporate it. In humid conditions, cotton activewear may never fully dry between exercises.
When Cotton Works
Despite its limitations, cotton excels in certain scenarios. For low-intensity activities like stretching, light yoga, or walking, cotton's softness and breathability provide unmatched comfort. Cotton is also ideal for casual, everyday wear where performance isn't critical.
Cotton's environmental credentials deserve mention—it's biodegradable, renewable, and often available in organic versions. For environmentally conscious consumers who prioritise sustainability over performance, cotton remains a valid choice.
Cotton Limitations
- Absorbs and holds moisture against skin
- Becomes heavy when wet
- Slow to dry
- Can cause chafing during intense exercise
- Prone to shrinkage if not pre-treated
- Wrinkles easily
Polyester: The Performance Standard
Polyester dominates modern activewear because its properties align perfectly with exercise demands. Most technical tank tops, regardless of brand, use polyester or polyester-based fabrics.
The Science of Moisture Wicking
Unlike cotton, polyester fibres are hydrophobic—they repel water rather than absorbing it. When engineered into specific weave patterns, polyester fabrics create channels that draw moisture away from skin through capillary action. The moisture spreads across the fabric surface, increasing the area available for evaporation and accelerating the drying process.
Brand-name technologies like Nike Dri-FIT, Under Armour UA Tech, and Adidas Climalite are essentially engineered polyester fabrics with optimised weave structures for enhanced wicking performance.
Durability and Care
Polyester is remarkably durable. It resists stretching, shrinking, and wrinkling far better than natural fibres. Polyester activewear maintains its shape and performance through hundreds of wash cycles when cared for properly.
Environmental Considerations
Polyester is petroleum-derived, raising sustainability concerns. However, recycled polyester (rPET) made from plastic bottles offers an environmentally friendlier alternative with identical performance. Many brands now offer recycled options—look for terms like "recycled polyester" or "rPET" on labels.
- Excellent moisture wicking
- Quick drying
- Lightweight
- Shape retention
- Wrinkle resistant
- Durable and long-lasting
- Easy to care for
Nylon: Premium Performance
Nylon offers similar moisture-wicking properties to polyester but with some distinct advantages that justify its often higher price point.
Nylon Characteristics
Nylon is softer and more comfortable against skin than most polyester fabrics. It drapes better, providing a more flattering fit for form-fitting activewear. Nylon is also more abrasion-resistant, making it ideal for activities where fabric rubs against surfaces or equipment.
Nylon dries slightly slower than polyester but still vastly outperforms cotton. Its exceptional stretch and recovery properties make it popular in compression wear and sports bras.
Common Applications
You'll find nylon in premium activewear, swimwear, and products requiring superior stretch. Lululemon's popular Luon fabric, for example, uses nylon as its primary component.
Elastane (Spandex/Lycra): The Stretch Factor
Elastane—marketed as Spandex in Australia and Lycra by DuPont—isn't typically used alone but is blended with other fabrics to add stretch. Understanding elastane content helps predict how garments will fit and perform.
Stretch Mechanics
Elastane fibres can stretch up to 600% of their original length and return to shape. Even small percentages (3-5%) dramatically improve a fabric's flexibility. Higher percentages (15-20%) create compression garments that support muscles during activity.
Reading Fabric Labels
When you see "92% Polyester, 8% Elastane" on a label, you're looking at a fabric designed for movement. The polyester provides moisture management while elastane ensures the garment stretches with you. Higher elastane content generally indicates more stretch and compression.
Elastane degrades when exposed to high heat. Tumble drying on high heat or ironing fabrics with elastane content will permanently damage the stretch fibres. Always air dry or use low heat settings.
Emerging Natural Alternatives
Bamboo Viscose
Bamboo-derived fabrics offer an interesting middle ground between natural and synthetic performance. Bamboo viscose wicks moisture effectively (though not quite as well as polyester), feels exceptionally soft, and has natural antibacterial properties that resist odour development.
The sustainability story is complicated—while bamboo grows quickly without pesticides, the viscose manufacturing process uses chemicals. "Closed-loop" bamboo production methods recycle these chemicals, offering better environmental credentials.
Merino Wool
High-performance merino wool challenges assumptions about natural fibres in activewear. Unlike standard wool, fine merino fibres don't itch and can be worn against skin comfortably. Merino naturally regulates temperature (warm when cold, cool when warm) and resists odour remarkably well.
Merino's main drawbacks are cost (significantly more expensive than synthetics) and durability (it wears out faster and requires careful washing). However, for multi-day activities where washing isn't possible, merino's odour resistance makes it invaluable.
Blends: The Best of Both Worlds
Many activewear items use fabric blends that combine the advantages of multiple materials.
Cotton-Polyester Blends
Common ratios like 60/40 or 50/50 cotton-polyester aim to deliver cotton's softness with improved moisture management. These blends work well for lighter exercise and casual athletic wear. They're often more affordable than pure performance fabrics.
Polyester-Nylon Blends
Combining polyester's wicking performance with nylon's softness and durability creates premium activewear fabrics. These blends are common in higher-end products.
Tri-Blends
Some fabrics blend three or more materials—commonly cotton, polyester, and rayon. These "tri-blend" fabrics aim for ultimate comfort with reasonable performance, often used in lifestyle and athleisure products.
Matching Fabrics to Activities
High-Intensity Cardio
For running, HIIT, or spin classes, choose 100% polyester or polyester-elastane blends. Maximum moisture wicking is essential when you're generating significant sweat.
Weight Training
Lifting allows more fabric flexibility since sweat production is typically lower than cardio. Cotton-blend tank tops work fine, though synthetic fabrics still offer advantages for longer sessions.
Yoga and Pilates
Stretch is paramount. Look for fabrics with 10%+ elastane content. Nylon blends provide the soft feel and flexibility these activities require.
Everyday Athleisure
For casual wear, prioritise comfort and style over technical performance. Cotton and cotton blends deliver the relaxed feel appropriate for non-exercise activities.
Understanding fabric composition transforms activewear shopping from guesswork to informed decision-making. Read those labels, consider your specific needs, and choose materials that support rather than hinder your activities.