Soft shoe comprising an external sole unit and an upper, the external sole unit comprising a cushioning sole, the cushioning sole extending lengthwise from a rear end as far as a front end, widthwise between a lateral side and a medial side, and heightwise from a lower face as far as an upper face, the lower face having lower grooves (11, 21, 27, 33, 37, 43), the upper face having upper grooves (14, 24, 30, 35, 40, 45, 47), the lower grooves of the lower face being opposite upper grooves of the upper face, characterized in that the lower grooves (11, 21, 27, 33, 37, 43) of the lower face and the upper grooves (14, 24, 30, 35, 40, 45, 47) of the upper face correspond to the main joints of the foot, in that the lower grooves of the lower face and the upper grooves of the upper face delimit platforms (48 to 68) of the cushioning sole, in that the lower face has a lower longitudinal groove which extends from a rear limit as far as a front limit, the rear limit being distant from the rear end by a distance comprised between 0 and 20% of the length of the cushioning sole, the front limit being distant from the front end by a distance comprised between 0 and 20% of the length of the cushioning sole, the lower longitudinal groove curving over a portion comprised between 80 and 100% of its length, the lower longitudinal groove having a rear point of inflection situated distant from the rear end at a distance comprised between 30 and 60% of the length of the shoe, the lower longitudinal groove having a front point of inflection situated distant from the front end at a distance comprised between 10 and 30% of the length of the shoe, the lower longitudinal groove deviating from the medial side towards the lateral side between the rear limit and the rear point of inflection, the lower longitudinal groove deviating from the lateral side towards the medial side between the rear point of inflection and the front point of inflection, the lower longitudinal groove deviating from the medial side towards the lateral side between the front point of inflection and the front limit, in that the upper face has an upper longitudinal groove which extends from a rear limit as far as a front limit, the rear limit being distant from the rear end by a distance comprised between 0 and 20% of the length of the cushioning sole, the front limit being distant from the front end by a distance comprised between 0 and 20% of the length of the cushioning sole, the upper longitudinal groove curving over a portion comprised between 80 and 100% of its length, the upper longitudinal groove having a rear point of inflection situated distant from the rear end at a distance comprised between 30 and 60% of the length of the shoe, the upper longitudinal groove having a front point of inflection situated distant from the front end at a distance comprised between 10 and 30% of the length of the shoe, the upper longitudinal groove deviating from the medial side towards the lateral side between the rear limit and the rear point of inflection, the upper longitudinal groove deviating from the lateral side towards the medial side between the rear point of inflection and the front point of inflection, the upper longitudinal groove deviating from the medial side towards the lateral side between the front point of inflection and the front limit, and in that the lower longitudinal groove is opposite the upper longitudinal groove.