A sport shoe comprises a sole and an upper portion attached to the sole and defining an inner space with the sole, and having an entrance opening for receiving a user's foot therethrough, into the inner space, and an attachment system to secure the user's foot therein, the sport shoe having, in longitudinal succession, a heel cage, a middle section, and a toe box, the middle section having at least four generally transversally-oriented strips in the upper portion, including tightening strips receiving the attachment system externally and having a heat-moldable layer internally, and flexibility strips, the tightening strips and flexibility strips being in longitudinally alternating succession, at least a section of the flexibility strips being heat moldable layer free.