Reinforcement learning apparently kept this running posture over human form

A person swings the arms mainly to stop the upper body from twisting with every stride, the twist that each leg puts into the torso. A robot arm is motors, gears, and wires. fast swinging will generate high torque, over and over, for a full lap.

The forward lean puts the mass where speed wants it. It shifts the center of mass ahead of the feet. For a biped, that can mean less time fighting to stay upright and more of each step going into forward motion.

https://t.co/9iVnNu0zhQ