The PureMove sports bra incorporates sheer thickening fluid, a substance developed at the University of Delaware, which has already incorporated into spacesuits to protect astronauts from shrapnel and into bullet-proof vests.
The fluid has a unique characteristic: it is more liquid when still or slightly agitated, and becomes harder in response to faster movement.
Its use at Reebok was spearheaded by Danielle Witek, a senior innovation apparel designer who read about the University of Delaware's innovation and thought it could form the basis of a new approach to sports bras.
The brand said that these bras typically rely on a structured design, with multiple layers of material, bonding, straps and hardware to give firm support.
People who participate in multiple sports will often have multiple sports bras, because the firm support required when running and jumping might create a distracting amount of compression when you're sitting on a yoga mat.
Others avoid exercise all together. Reebok — which has been wholly owned by Adidas since 2005 — points to statistics from a 2014 survey that showed one in five women were put off exercising because of breast discomfort. They ranked it as a more common barrier to exercise than cost and access to facilities.
Sheer thickening fluid, developed at the University of Delaware, is used in NASA spacesuits to protect astronauts from shrapnel
To address these issues, Witek wanted to create a single bra that would firm up during high-impact exercise and relax for a looser fit during low-impact exercise or rest.
Reebok worked with the University of Delaware to create a fabric woven with the sheer thickening fluid. The brand calls the resulting proprietary textile Motion Sense Technology.
A total of seven pieces of fabric come together in the construction of what Reebok describes as a "minimalist" garment.
"Many would assume that the more support a sports bra gives would equate to the more fabric, straps or hooks it's comprised of," said Witek. "However, by utilising our Motion Sense Technology, PureMove's design is quite deliberately the opposite."
"The minimalist design of the bra may seem deceiving when you first hold it, but you should not confuse this for lack of support or technology," she continued. "Every single detail is intentional and directly informed by years of our testing and research."
The PureMove sports bra is one of the first mainstream items of clothing to incorporate an "active material". These are materials that change their characteristics on demand, usually in response to temperature or pressure changes, like MIT's Liquid Printed Pneumatics and Active Auxetic material.
The PureMove bra will be available in 10 sizes on the Reebok website from August 17 and from third-party retailers at the end of the month.