ULTRALIGHT FLEXIBILITY FOR EVERYDAY WORKOUTSThe Nike Free TR 4 Mezzo Print Women's Training Shoe is lighter than its predecessor with a revolutionary upper that uses breathable engineered mesh. Plus, the Nike Free 5.0 platform offers training-specific flexibility and traction.BenefitsUltralight Flywire technology offers dynamic support for your forefootComfort collar wraps the heel for a supportive fit and feelFlex grooves help enhance flexibility and natural range of motionBreathable, engineered mesh upper with lightweight synthetic backing for ventilation and supportPhylite midsole for lightweight, durable cushioningEnvironmentally-preferred rubber pods in the heel and forefoot for durability on a variety of surfacesProduct DetailsHerringbone pattern in the forefoot for multidirectional tractionWeight: 12 ounces (based on women's size 7)Nike Free OriginsAfter 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.