The pinnacle of Ryka performance, the Vida RZX Training Sneaker features the new RZX technology platform. RZX innovates to provide BOTH flexibility and cushioning in a training shoe - she no longer has to decide between the two. Featuring Ultra Flex in the forefoot, the alternating flex grooves on the top and bottom of the midsole, and in the rubber outsole, RZX reduces forefoot pressure during workouts. RZX features RE-ZORB in the heel, designed to absorb impact and provide cushion all the way