Shoe having an improved upper

Shoe (1) including an outer sole assembly (2) and an upper (3), the shoe (1) extending lengthwise from a rear end (4) to a front end (5), widthwise between a lateral side (6) and a medial side (7), and height-wise from the sole assembly (2) to an upper end (12), the upper end (12) demarcating a rear opening (13), the upper (3) including a first envelope (14), characterized in that the first envelope (14) includes a rear portion (20), which itself includes a lateral wall (21), a rear wall (22), and a medial wall (23), the rear portion (20) being at least partially porous or having low resistance to the passage of a fluid, and in that the first envelope (14) includes a front portion (25), which itself includes a lateral wall (26), a front wall (27) and a medial wall (28), the front portion (25) being resistant to the passage of a fluid or being impervious.