Ryka Vida Rzx Women's Athletic Training Sneaker. The Vida RZX features the RZX technology platform. With 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. The RE-ZORB® in the heel is designed to absorb impact and provide cushion all the way to the flex zone. Model: RYKA-VIDA_RZX.