People do not always watch their steps and yet most of the time they do not fall. Researchers have now found out how people maintain the balancing act.
Each step can be thought of as a small move intended to help people recover stability after a very tiny fall - a microcosm of the larger, more dramatic moves we employ to stay vertical when something knocks us off balance, the findings showed.
"Our bodies initiate an almost imperceptible fall to the right before taking a step to the right, and a fall to the left before taking a step to the left," the study noted.
If our pelvis happens to move a millimetre differently one way or the other in a particular step, it creates a tiny imbalance, which we seem to compensate for by placing the next step in an appropriate position.
This all happens without conscious thought on our part, the researchers found.
"Every step we take is a balancing act as the body falls forward and sideways," explained Manoj Srinivasan, an assistant professor at the Ohio State University in the US.
"We were able to show that the next foot position can be predicted way in advance of when the foot is placed - as early as the middle of the previous step," he added.
The researcher developed a mathematical model that can explain over 80 percent of the apparent randomness in the location of a person's next step, based only on tiny variations in the movement of that person's pelvis.
They fitted 10 participants with motion capture markers and tracked them walking on a treadmill at various speeds, from a leisurely stroll to a moderate pace.
The study revealed a simple structure in normal walking variability so deviations from that structure would indicate the nature of someone's difficulty.
A better understanding of the human gait could inform the design of assistive exo-skeletons that help people with movement disorders walk naturally.
The study appeared in the journal Biology Letters.
