When the cause is found, cramping can be due to prolonged sitting or leg position during sedentary activity.

CNN: What causes leg cramps?

They placed him as anchor, the final leg, and a position he'd rarely run.

WSJ: Social Media

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.

ENGADGET: AMP-Foot 2.0 prosthesis gives the power of real feet, keeps a light step (video)