FLEXIBLE MEETS FAST The Nike Free Express (3. 5y-7y) Kids' Running Shoe features a flexible outsole for a more natural stride and a breathable, lightweight mesh upper to help you move fast while your feet stay cool. Flexibility Flex grooves along the length and width of the outsole allow your foot to move naturally for a greater range of motion and stability. Enhanced Ventilation Bonded mesh and strategically placed perforations create a seamless, breathable upper to help keep your feet cool and comfortable. Impact Protection Waffle pistons in the outsole work with the Phylite midsole to help absorb impact for softer landings. Easy On and Off A pull tab on the heel makes getting this shoe on and off a breeze. More Benefits Phylite midsole is durable enough to double as an outsole, dramatically reducing the overall weight Abrasion-resistant BRS 1000 carbon rubber under the heel for durability Strategically placed sections of solid rubber under the toe for traction Nike Free Origins After learning that Stanford athletes had been training barefoot on the university's golf course, three of Nike's most innovative and creative employees set out to develop a shoe that felt natural and weightless, similar to bare feet. In 2002, they examined a group of men and women with pressure-measuring insoles taped to their feet, using high-speed cameras to capture images of each foot in motion. The team spent eight years studying the biomechanics of shoeless running. The results yielded a profound understanding of the foot's natural landing angle, pressure and toe position, allowing Nike designers to build an unconventional and flexible running shoe from the inside out.