It was five years ago that prosthetics took a very literal step forward when Arizona State University's SPARKy foot offered a more natural walk, capturing the inherent kinetic energy that previously needed a big motor to replicate. Belgium's Vrije Universiteit Brussel may well carry the torch for the next wave of artificial limbs. Its second-generation Ankle Mimicking Prosthetic Foot (AMP-Foot 2.0) uses a pair of force sensors to determine the leg's relative position and let an actuator build energy when the foot bends, locking the power away to use only when the owner pushes off. The efficiency produces all the torque needed to let a 165-pound person walk, but with just a 30W to 60W motor versus SPARKy's 150W -- a big help to battery life that also reduces the AMP-Foot 2.0's weight to that of the fleshy kind. We don't know how likely it is the Belgian prosthesis goes beyond the prototype phase; if we had our way, it would move just as quickly as future wearers undoubtedly will.