科学美国人60秒:To Walk, You Have to Fall in Step

How many times has this happened to you? You start to fall, but then catch yourself and continue on your way. Well, new research shows that falling and catching yourself actually happens every time we take a step. And that we precisely place our feet as we walk to avoid taking a tumble during this ambulatory balancing act. The study is in the journal Biology Letters. [Yang Wang and Manoj Srinivasan: Stepping in the direction of the fall: the next foot placement can be predicted from current upper body state in steady-state walking]

When humans walk, we put one foot in front of the other. But the way each foot lands can vary from step to step. This variation in foot placement can appear pretty random. But researchers decided to take a closer look. 

They fitted 10 volunteers with motion caption markers and then watched as the subjects walked on a treadmill. The investigators discovered that that they could predict exactly where each foot would fall based on the movement of the person’s pelvis during the previous step. The body falls forward and sideways as we walk…and the feet come down in a way that restores our balance.

The findings could be useful for developing ways to help people with movement disorders regain their stability. The info could also make walking robots more surefooted. So they don’t, ya know, fall down on the job. 

—Karen Hopkin