By watching people on a treadmill, researchers including one of Indian-origin have gained new insight into how the body moves when we are walking and the role our feet play in maintaining balance.
In normal walking, humans place their foot at slightly different positions on each step. To the untrained eye, this step-to-step variation in foot position just looks random and noisy, researchers at The Ohio State University noted.
The researchers describe a mathematical model that can explain over 80 per cent of this apparent randomness in the location of a person's next step, based only on tiny variations in the movement of that person's pelvis.
Every step we take is a balancing act as the body falls forward and sideways, said Manoj Srinivasan, assistant professor of mechanical engineering and the head of the Movement Lab at Ohio State.
"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 - based on how the body is falling," he said.
"Nobody knew that such high predictability was possible with such a simple model and with only normal walking data," said Srinivasan.
What they learned may one day inform the design of assistive exoskeletons or walking robots - or just help doctors diagnose and treat balance problems.
The idea of the study, said former doctoral student Yang Wang, was to capitalise on the natural variability in how we place our steps when walking normally.
Each step can be thought of as a small move intended to help us 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.
Researchers 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 (from around 2 to 3 miles per hour).
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, researchers said.
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, researchers said.
The study was published in the journal Biology Letters.
