Flexible insole suitable for being arranged in an item of footwear under the foot of a wearer, said sole comprising a front part and a rear part intended to respectively receive the front of the foot and the heel, and a flexible intermediate part connecting the front part and the rear part, said insole comprising, on the plantar side, an eversion and inversion module comprising: - a first reinforcing element straddling the rear part and the intermediate part and having: a) a first anatomical area comprising a first arch intended to follow the inner part of the wearer's foot, extending substantially along the joints between the calcaneus, the talus, the navicular bone and the medial cuneiform bone, and b) a second anatomical area comprising a second arch intended to follow the outer part of the wearer's foot, extending substantially along the joints between the calcaneus, the cuboid and the fifth metatarsal; and - a second reinforcing element located in the rear part and having: c) a third anatomical area intended to be in contact with the peroneal tubercle, and d) a fourth anatomical area intended to be in contact with the calcaneus, the cuboid and/or the fifth metatarsal, characterised in that said first and second reinforcing elements are arranged to cooperate together such that a compression of the module at the rear part causes a bending of the first and third areas causing, by compensation with the second and fourth areas, a twisting movement of the intermediate part in the axial direction of said sole and a lifting of the front part relative to the intermediate part, wherein the intermediate part comprises in its middle part a strip substantially transversely curved and longitudinally arched between the front edge and the rear edge of the intermediate part, said first and second areas being arranged at the intermediate part on either side of said strip, and wherein the radius of curvature of said strip is dimensioned to form a median retro-capital support at the rear of the metatarsal heads of the foot when said foot rests on said sole. said insole comprising, on the plantar side, an eversion and inversion module comprising: - a first reinforcing element straddling the rear part and the intermediate part and having: a) a first anatomical area comprising a first arch intended to follow the inner part of the wearer's foot, extending substantially along the joints between the calcaneus, the talus, the navicular bone and the medial cuneiform bone, and b) a second anatomical area comprising a second arch intended to follow the outer part of the wearer's foot, extending substantially along the joints between the calcaneus, the cuboid and the fifth metatarsal; and - a second reinforcing element located in the rear part and having: c) a third anatomical area intended to be in contact with the peroneal tubercle, and d) a fourth anatomical area intended to be in contact with the calcaneus, the cuboid and/or the fifth metatarsal, - a first reinforcing element straddling the rear part and the intermediate part and having: a) a first anatomical area comprising a first arch intended to follow the inner part of the wearer's foot, extending substantially along the joints between the calcaneus, the talus, the navicular bone and the medial cuneiform bone, and b) a second anatomical area comprising a second arch intended to follow the outer part of the wearer's foot, extending substantially along the joints between the calcaneus, the cuboid and the fifth metatarsal; and a) a first anatomical area comprising a first arch intended to follow the inner part of the wearer's foot, extending substantially along the joints between the calcaneus, the talus, the navicular bone and the medial cuneiform bone, and b) a second anatomical area comprising a second arch intended to follow the outer part of the wearer's foot, extending substantially along the joints between the calcaneus, the cuboid and the fifth metatarsal; and - a second reinforcing element located in the rear part and having: c) a third anatomical area intended to be in contact with the peroneal tubercle, and d) a fourth anatomical area intended to be in contact with the calcaneus, the cuboid and/or the fifth metatarsal, c) a third anatomical area intended to be in contact with the peroneal tubercle, and d) a fourth anatomical area intended to be in contact with the calcaneus, the cuboid and/or the fifth metatarsal, characterised in that said first and second reinforcing elements are arranged to cooperate together such that a compression of the module at the rear part causes a bending of the first and third areas causing, by compensation with the second and fourth areas, a twisting movement of the intermediate part in the axial direction of said sole and a lifting of the front part relative to the intermediate part, wherein the intermediate part comprises in its middle part a strip substantially transversely curved and longitudinally arched between the front edge and the rear edge of the intermediate part, said first and second areas being arranged at the intermediate part on either side of said strip, and wherein the radius of curvature of said strip is dimensioned to form a median retro-capital support at the rear of the metatarsal heads of the foot when said foot rests on said sole.