Our softest leggings yet: The engineering behind SenseTec™

The search for soft leggings usually starts with a simple desire, comfort, but often ends in compromise.

Softness is determined by how a fabric is built – from fiber selection to knit structure to finishing. Most leggings rely on mechanical brushing to create that soft, fuzzy feel. And it works. But that softness sits on the surface and it can fade with heat, friction, and movement.

SenseTec™ takes a different approach. Through Swiss engineering, it’s designed to feel as refined in motion as it does at rest – so nothing interrupts the run.

The rise of soft and buttery-soft leggings reflects a broader trend in athletic wear: performance alone is not enough. You expect comfort that carries you through every part of your day. This demand for a luxe, weightless feel has pushed the industry to evolve and move beyond surface treatments toward more considered textile engineering.

While brushing processes create an immediate soft sensation, it can compromise the fabric’s structural integrity. These materials tend to trap heat and lose their supportive fit during high-intensity movement.

Performance usually requires a tradeoff. Traditionally, you might have a secure fit that can withstand the friction of a run or a gym session, but that would come with a stiffer, more abrasive textile. This leaves the choice between a pair that feels good on the couch, and a pair that performs during a workout.

This friction point is an engineering problem. SenseTec™ addresses this by balancing softness with durability. “This is through a precise combination of yarn selection and knitting engineering,” says Aleksandra Rakic, Senior Apparel Material Developer at On.

The result provides the technical security required for movement without sacrificing the refined, weightless sensation.

Soft against your skin and smooth to the touch, SenseTec™ fabric feels effortless. But that feel is the result of precise engineering. Rather than relying on surface-level brushing, SenseTec™ is built from the fiber up. 

Knit

Swiss-engineered with just the right amount of stretch, it adapts to your body and allows you to move without resistance.

“A 32-gauge interlock knit structure combines N66 40D elastane, creating a fabric that feels smooth against the skin,” says Rakic. “This paired with a 48-filament yarn refines the surface at a microscopic level, resulting in a suede-like premium touch.”

Plus, customized loop formation and precisely controlled knitting tension create a stable fabric with controlled elasticity. The refined surface finish contributes to the fabric's smooth hand-feel without compromising breathability or stretch.

Stretch 

Softness without structure doesn’t last. SenseTec™ is designed to do both.

“Its single-sided elastane-dominant structure uses polyamide and 55D elastane to deliver a soft, flexible stretch with a supportive hold,” Rakic says. This allows the fabric to move with the body while maintaining its original shape during high-intensity sessions.

This means there’s a strong recovery for the fabric that resists sagging or bagging, even after extended wear or repeated movement.

Performance 

Beyond the initial touch, SenseTec™ is built for movement. The moisture-wicking properties keep the body cool and dry, while the matte finish provides a distraction-free, studio-to-street aesthetic.

Breathability and moisture-management

Softness means nothing if the fabric can’t perform under pressure. SenseTec™ is engineered with a structure that promotes airflow, allowing heat to escape more efficiently than typical lifestyle-oriented yoga fabrics. A moisture-wicking finishing treatment further enhances this, helping draw sweat away from your skin and speed up evaporation.

Together, these elements create a well-balanced fabric that stays dry, breathable and consistent, making the fabric suitable for an intense gym session or everyday errands.

Fiber content

We engineered this fabric to balance the lightest weight with opacity while delivering soft hand wear after wear. The result is a lightweight fabric that remains opaque, supportive and comfortable through workouts, recovery days and everyday movement.

Durability

The SenseTec construction ensures the leggings are “squat-proof” and reliable – from long runs to repeated washes – without losing their original feel. The materials go through performance and opacity testing.

“It [is] a three-fold [process] to ensure that, in every scenario, we have considered what that opacity could look like,” Annaleigh Hockaday, On’s Global Senior Director of Product, describes. “We put this tight on hundreds of women, and then we got them to engage in a Pilates or a yoga class so that we could monitor how it performed in real time.”

Material blends 

SenseTec™ combines 73% recycled polyamide and 27% elastane. The elevated elastane content is key to the fabric’s feel, creating soft support, dynamic stretch and strong shape recovery. Long-lasting performance was validated through rigorous lab and wear testing.

Most soft leggings prioritize immediate hand-feel that’s plush at first touch but fades over time and through movement. SenseTec™ takes a different approach. Instead of engineering surface-level softness, it’s woven directly into the fabric's DNA, creating a streamlined design that holds up through motion. Plus, SenseTec™’s elimination of a front seam reduces friction, and an integrated phone pocket keeps essentials secure.

The search for the perfect pair of leggings usually ends where performance begins.

By moving beyond the surface-level trend of soft leggings, SenseTec™ offers a solution for athletes who refuse to choose between comfort and capability. With a durable and dynamic construction, it is gear intentionally designed to be felt, then forgotten, so you can focus on the movement itself.