The invention is an article of footwear having an upper and a sole structure. The sole structure includes a moderator plate and a traction plate. The moderator plate is attached to the upper and the traction plate is attached to the moderator plate, thereby forming a void between the plates. The traction plate functions as a ground-engaging portion of the sole and includes a plurality of projections that provide traction. In addition, the projections may be structured to attenuate impact forces and absorb energy during the running cycle.