A sole structure for an article of footwear , comprising: a forefoot support component ; a heel support component ; and a midfoot flex component comprising a bi-stable spring element engaging the forefoot support component and the heel support component , wherein the midfoot flex component includes a medial side edge , a lateral side edge , and an intermediate portion extending between the lateral side edge and the medial side edge , and wherein the midfoot flex component is movable between a closed position and an open position, wherein: in the closed position, at least a portion of the midfoot flex component has a transverse cross sectional shape extending in a direction from the medial side edge to the lateral side edge in which the intermediate portion of the midfoot flex component curves in a first direction from a local extrema located in the intermediate portion , and in the open position, at least said portion of the midfoot flex component has a transverse cross sectional shape extending in the direction from the medial side edge to the lateral side edge in which the intermediate portion of the midfoot flex component is substantially flat or curves in a second direction from a local extrema located in the intermediate portion , wherein the second direction is opposite from the first direction. a forefoot support component ; a heel support component ; and a midfoot flex component comprising a bi-stable spring element engaging the forefoot support component and the heel support component , wherein the midfoot flex component includes a medial side edge , a lateral side edge , and an intermediate portion extending between the lateral side edge and the medial side edge , and wherein the midfoot flex component is movable between a closed position and an open position, wherein: in the closed position, at least a portion of the midfoot flex component has a transverse cross sectional shape extending in a direction from the medial side edge to the lateral side edge in which the intermediate portion of the midfoot flex component curves in a first direction from a local extrema located in the intermediate portion , and in the open position, at least said portion of the midfoot flex component has a transverse cross sectional shape extending in the direction from the medial side edge to the lateral side edge in which the intermediate portion of the midfoot flex component is substantially flat or curves in a second direction from a local extrema located in the intermediate portion , wherein the second direction is opposite from the first direction. in the closed position, at least a portion of the midfoot flex component has a transverse cross sectional shape extending in a direction from the medial side edge to the lateral side edge in which the intermediate portion of the midfoot flex component curves in a first direction from a local extrema located in the intermediate portion , and in the open position, at least said portion of the midfoot flex component has a transverse cross sectional shape extending in the direction from the medial side edge to the lateral side edge in which the intermediate portion of the midfoot flex component is substantially flat or curves in a second direction from a local extrema located in the intermediate portion , wherein the second direction is opposite from the first direction. <EOS>