An article of footwear having an upper and a sole structure secured to the upper, the sole structure comprising: a midsole formed from a foamed polymer material and positioned adjacent to the upper; a first impact-attenuating member located in a heel portion of the sole structure; an upper plate embedded within the midsole and formed from a non-foamed polymer material having an upper surface oriented toward the upper and an opposite lower surface oriented away from the upper; a first leg formed from a non-foamed polymer material extending downward from the lower surface of the upper plate away from the upper, a lower portion of the first leg forming a portion of the first impact-attenuating member; an outsole at a bottom portion of the article of footwear opposite the upper configured to engage the ground during use; and a user-adjustable control configured to modify impact-attenuation characteristics of the sole structure based on receiving adjustment settings from the user, wherein the first leg lower portion is configured to provide adjustable impact-attenuation characteristics for the first impact-attenuating member; the article of footwear further comprising a lower plate oriented generally parallel with the upper plate and forming an upper region of the outsole. characterized in that the first leg forms a hollow container extending downward away from the upper, the hollow container having an opening at its distal end and forming a gap between the distal end and the outsole when the article of footwear is in a relaxed state without receiving downward impacts, the sole structure further comprising a compressible plug disposed partially within the first leg hollow container, extending through the distal end opening, and being disposed partially within the gap between the first leg hollow container distal end and the outsole, the gap is formed between the distal end opening and the upper surface of the lower plate. a midsole formed from a foamed polymer material and positioned adjacent to the upper; a first impact-attenuating member located in a heel portion of the sole structure; an upper plate embedded within the midsole and formed from a non-foamed polymer material having an upper surface oriented toward the upper and an opposite lower surface oriented away from the upper; a first leg formed from a non-foamed polymer material extending downward from the lower surface of the upper plate away from the upper, a lower portion of the first leg forming a portion of the first impact-attenuating member; an outsole at a bottom portion of the article of footwear opposite the upper configured to engage the ground during use; and a user-adjustable control configured to modify impact-attenuation characteristics of the sole structure based on receiving adjustment settings from the user, wherein the first leg lower portion is configured to provide adjustable impact-attenuation characteristics for the first impact-attenuating member; the article of footwear further comprising a lower plate oriented generally parallel with the upper plate and forming an upper region of the outsole. characterized in that the first leg forms a hollow container extending downward away from the upper, the hollow container having an opening at its distal end and forming a gap between the distal end and the outsole when the article of footwear is in a relaxed state without receiving downward impacts, the sole structure further comprising a compressible plug disposed partially within the first leg hollow container, extending through the distal end opening, and being disposed partially within the gap between the first leg hollow container distal end and the outsole, the gap is formed between the distal end opening and the upper surface of the lower plate.