Since its inception in 2004 by Tobie Hatfield and Eric Avar, Nike Free has undergone numerous updates. The Nike Free RN 2018 PS 'Gym Blue' shows the modifications of the adult shoe in bold contrast, including a Dynamic Fit inner sleeve and flexible back heel strap to lock down the foot without impeding it. Other upgrades include a rounded heel that rolls with the ground, and spandex integrated with the circular-knit upper and laces for more natural movement.