Worn inside on a treadmill with very little use. Design: 3D Fit Print technology in the upper provides structure that moves with you GuideRails® provide a holistic support system and align your body into its natural motion path Put your feet first with the APMA Seal of Acceptance In-Shoe Comfort: 100% DNA LOFT midsole combined with a segmented crash pad for a seamless transition from the heel to toe-off