Grooves on the outsole expand and flex with your foot.
the Free TR 8 trainer is designed to provide the stability and support you need. Full-bootie construction with a midfoot flywire cable system creates a firm, sock-like fit, while the updated, flatter heel provides a wider surface area to keep you steady on your feet.
The Nike Free TR8 Women's Training shoe has a stronger heel than ever before, plus extra cushioning that hugs and contains your foot. The sole is still unbelievably flexible, offering a natural, lightweight feel and lateral support through every rep.