A shoe insert including a bladder positioned within a main body. The bladder includes a fluid tight membrane defining an interior chamber containing a liquid. The bladder further includes a heel portion in fluid communication with lateral and medial passages, which are in turn in fluid communication with a metatarsal portion. A central island of solid material is bounded by the heel portion, the lateral and medial passages, and the metatarsal portion, such that the bladder is configured to move liquid contained within the interior chamber in a cycle that conforms to a natural gait cycle.