Principle number five: Humane technology doesn't outsource people, but instead empowers them. How healthy or humane is it to have an escalator to the gym? Humane technology should not aim to replace the human mind and body. Rather, it should be used as a tool to augment existing capabilities. The Cheetah Flex-Foot, a prosthetic foot and lower leg, integrates with a user's existing knee and upper leg to enable comfortable walking and running. Users are at least as fast as those with flesh-and-blood feet, and may even be faster thanks to the mechanical efficiencies of springy metal. The initial design was closely modeled on the human foot, but evolved into a sleeker blade-like shape that's more cheetah than person. The Flex-Foot is therefore not an exact replacement for the human form, but a way to radically re-imagine it.