Legs & Springs

Legs & Springs

Gravity is the main obstacle to locomotion on land. It pulls us down with each step, but our momentum and internal springs redirect this force to our advantage. By shifting our balance, we push against the ground for propulsion.

Animals have evolved diverse numbers of legs and different patterns of movement (gaits) for varying speed and efficiency. Some have two, four, six, or hundreds of legs that they use to skitter, hop, and run across Earth’s uneven surfaces.

But it’s not just about the legs. Other features make an animal’s entire body built for speed. An animal’s posture and how it carries its weight affects how fast it can go. A major trend in vertebrates (animals with backbones) is that the sprawling stance of amphibians has evolved repeatedly into a more upright carriage with legs directly under the body.

Scientists have long been working to mimic the complex biomechanics of a human. The curved, carbon-fiber foot, while still not quite as efficient as a natural leg, possesses enough springiness that amputees can really run. And bipedal robots are well on their way to reproducing the human gait successfully, perhaps someday helping people formerly in wheelchairs to walk again.