Good activewear uses polyester or nylon for moisture-wicking, blended with elastane for stretch. Cotton absorbs sweat and holds it, which makes it the wrong choice for exercise in heat.
Here is what each fabric does and what to look for on a label.
Polyester
Polyester is the most common activewear fabric because it moves sweat away from the skin and dries fast.
- Strengths: excellent moisture-wicking, dries quickly, holds colour, durable, inexpensive
- Weaknesses: retains odour more than other fabrics, less soft than nylon
- Best for: most exercise, particularly in heat
Nylon
Nylon is softer and stronger than polyester, and usually more expensive.
- Strengths: very soft, strong, good stretch recovery, resists abrasion
- Weaknesses: costs more, slightly slower to dry than polyester
- Best for: leggings and pieces worn against the skin
Elastane (spandex, Lycra)
Elastane is what gives activewear its stretch, and it is always blended, never used alone.
Look for roughly 10 to 25 percent elastane in leggings. Below 10 percent and they will bag out at the knees. Above 25 percent and they become compressive, which some people want and others do not.
Elastane is also the fibre destroyed by heat, which is why you never tumble dry activewear. See how to care for activewear.
Cotton
Cotton absorbs sweat and holds it, making it a poor choice for exercise. This is worth being clear about, because cotton is the default assumption for comfort.
Cotton is excellent for underwear gussets and for loungewear. It is poor for exercise, because it becomes heavy, damp and clinging, and increases chafing. In Karachi heat that difference is significant, not marginal.
See cotton versus synthetic underwear for the same trade-off in underwear.
What does moisture-wicking actually mean?
The fabric moves sweat from your skin to the outer surface, where it evaporates. It does not absorb sweat, it transports it.
That is the entire difference between technical fabric and cotton. Cotton soaks sweat up and holds it against you. Wicking fabric moves it outward and lets it evaporate, so you stay drier.
What should you look for on a label?
A polyester or nylon base with 10 to 25 percent elastane, and a gusset in leggings. A quick checklist:
- Fibre content: mainly polyester or nylon, with elastane for stretch
- Fabric weight: heavier means more opaque, which matters for leggings
- Flatlock seams: flat seams reduce chafing
- A gusset: a diamond or triangular panel at the crotch, which improves both fit and opacity
- Care instructions: if it says tumble dry, treat that as a warning rather than permission
What works best in Karachi's climate?
Lightweight polyester blends, in light colours, with a loose enough cut for airflow. Heat and humidity are the constraints.
In high humidity, even wicking fabric struggles because sweat evaporates slowly. What helps is airflow, so a slightly looser cut outperforms a tight compressive one in Karachi summer, even in the same fabric.
Frequently asked questions
Is cotton good for working out?
No. Cotton absorbs sweat and holds it against the skin, which becomes heavy and increases chafing. Polyester or nylon blends are far better for exercise.
What is the best fabric for leggings?
A nylon-elastane blend for softness, or polyester-elastane for faster drying. Look for 10 to 25 percent elastane and a decent fabric weight for opacity.
Why does my activewear smell even after washing?
Polyester holds odour more than natural fibres. Wash cold promptly after wearing, avoid fabric softener, and do not leave damp kit in a bag.
What is a gusset and why does it matter?
A separate fabric panel at the crotch of leggings. It improves fit, reduces seam pressure and adds opacity where fabric stretches most.
Where can I buy quality basics in Karachi?
Erblis delivers underwear, bras and loungewear across Karachi with free delivery and Cash on Delivery available. Use WELCOME10 for 10% off your first order.
The short version
Polyester or nylon base, 10 to 25 percent elastane, decent fabric weight, flatlock seams and a gusset. Save cotton for loungewear.