After viewing athletes training barefoot in 2002, Nike set out to develop an athletic shoe that would feel more natural and weightless, simulating barefoot running. They began to study a group of male and female athletes by taping pressure-measuring insoles to their feet and using high-speed cameras to capture images of each of their feet in motion.
The team spent eight years studying the biomechanics of barefoot running. The results provided a new understanding of the human foot-s natural landing angle, pressure, and toe position and enabled the Nike designers to build an unconventional and flexible shoe from the inside out: The Nike Free.
Nike Free running and training shoes are specifically designed to let your feet move more naturally and freely than traditional athletic shoes, providing all the benefits of barefoot running with the added cushioning and protection of a shoe. The shoe's upper works with the midsole to provide additional support without impeding the barefoot like experience.
Nike Free shoes are assigned a number between 0 and 10, and the lower the number in the shoe's name, the closer that shoe is to true barefoot running. On that scale, 10 would represent a conventional shoe, while zero would be truly barefoot. In other words, the Nike Free 3.0 offers more of a barefoot feel than the Nike Free 5.0, which provides more of the cushioning and protection of a regular athletic shoe.