PURE BOOST X TRAINING SHOES - The boost midsole on these women's training shoes is a game-changer with its endless supply of light, fast energy. These shoes gently hug feet with sock-like arch support, a lightweight frame and a flexible textile upper. A gap in the overlay at the arch supports the natural movement of your foot. boost's energy-returning properties keep every step charged with an endless supply of light, fast energy. Textile upper for lightweight flexibility. Adjustable forefoot and midfoot support. Sock-like construction for snug fit. Adaptive dynamic fit for optimal flexibility and smooth transition.