A differential-stiffness impact-attenuation member includes at least one spring element. The spring element has dimensions in height, length and width directions. The height dimension extends from a top surface to a bottom surface. The length dimension extends from a front end to a back end. At least one of the top and bottom surfaces is adapted for mounting. The impact-attenuation member has a first stiffness characteristic in the height direction at the front end of the spring element and a second stiffness characteristic in the height direction at the back end of the spring element. The spring element may define a cavity. A tension element may engage the spring element and be located at least partially within the cavity. The impact-attenuation member may engage at least one of a foot-covering member, a foot-supporting member and a surface-contacting member associated with a foot-receiving device.