Ask any woman who trains why she stopped wearing a particular pair of leggings and the answer is rarely "they wore out." It is almost always the same sentence: I bent over in class and realised.
Sheerness is the number one reason activewear gets abandoned, and the number one reason it gets returned. It is also almost entirely predictable. Here is what causes it, and how to test a pair you already own before you find out the hard way.
Three things make a legging go sheer
1. Knit density — the one you can't fix
Fabric weight is measured in grams per square metre. A lightweight knit feels wonderful in the hand and disappears under load: stretch it across the widest part of your thigh in a deep squat and the yarns separate far enough for light to pass between them. A denser knit has more yarn in the same area, so the same stretch opens smaller gaps.
This is the biggest single driver, it is decided at the mill, and no amount of careful washing will improve it. It is also why two pairs can feel identical on the hanger and behave completely differently in a squat.
2. Elastane recovery — the one that degrades
The stretch in your leggings comes from elastane, also sold as spandex. Elastane behaves like a spring: stretch it, and it pulls back. Three things shorten its life — heat, chlorine, and oil. A hot wash, a tumble dryer, a spa, a chlorinated pool, and body oils left sitting in unwashed fabric all take a toll.
When elastane stops recovering, the knit no longer returns to its original density after each wear. The fabric goes slack, sits looser on the leg, and needs less stretch to open up. A pair that was opaque when you bought it can be sheer within a year from dryer heat alone.
3. Fabric softener — the one nobody warns you about
Softener works by coating fibres in a thin waxy film. On cotton towels that feels pleasant. On a technical nylon-elastane knit it does two damaging things at once: it blocks the channels that move sweat away from your skin, and it builds up on the elastane, interfering with recovery.
The result is a legging that stops wicking, starts holding smell, and loses shape faster. If you currently use softener on your activewear, stopping is the single highest-value change you can make. Our fabric care guide has the full routine.
The 30-second opacity test
Do this in daylight, in front of a mirror, wearing the underwear you would normally train in. Patterned or contrasting is better, because it shows up what plain black hides.
- Squat to full depth. Not a half squat — sit all the way down, the way you would to pick something off the floor.
- Look at the seat and the outer thigh in the mirror, or ask someone. Those are the two areas under the most stretch.
- Repeat with a forward fold. Feet hip-width, hands towards the floor. This loads the fabric differently and catches pairs that pass the squat.
- Check either side of the seams. Fabric next to a seam is often thinner, because it was stretched during construction.
If you can see colour or texture through the fabric in any of those positions, the pair is not squat-proof. Nothing you do at home will change that.
Why we put "100% squat-proof" in writing
Both Mila and Valerie are knitted at a density chosen to stay fully opaque through a deep squat. Mila uses an 80/20 nylon-spandex blend. Valerie uses a heavier 75/25 compression knit built to hold under load.
If a pair of OXYGENA leggings is sheer under normal use, that is a fault, not a fit issue. Send them back for a replacement or a full refund including postage — your choice. A claim like that is worth exactly as much as the willingness to honour it, which is why it sits on every product page rather than buried in a policy.