Abstract: The present invention discloses a sole unit for shoes, sandals, boots, and other articles of footwear. The sole unit comprises at least one spring unit having at least a top wall and a bottom wall that define an opening to allow the top and bottom walls to converge under force, absorbing energy on impact and releasing energy on rebound. Variations in the longitudinal profile, transverse profile, spring-wall thickness, and spring-wall shape permit control over spring force in response to compression. A spring unit may further comprise one or more dampeners to modify the energy-storing properties of the spring unit. A spring unit may further comprise one or more bumpers that come into contact at predetermined distances when compressing the spring unit, to further modify the dynamic response of the spring under a load.