The Surprising Complexity of Walking

Next time someone tells you to watch your step, tell them you already are.

Placing your foot down when walking was thought to be a predetermined process: lift foot, decide where to put it based on what's on the ground, and if nothing moves, land it down on the original target. Scientists thought this procedure requires no immediate visual information once the foot was lifted off the ground.

But a new study has found that continuous visual guidance mechanisms may be needed for accurate foot placement.

"We have demonstrated that vision can be used in an online fashion to fine-tune foot placement during a step," said Raymond Reynolds, of the Institute of Neurology, Queen Square, London.  "It was previously thought that vision was used to plan the step in advance but not necessarily monitor its ongoing progress."

Reynolds and colleagues looked at how well people placed their feet onto a target in the process of walking. In half of their tests, they blocked off the subjects' vision as they were lifting their feet off of the ground. This caused them problems in placing their foot accurately on the target. When vision was restored, foot placement was once again on the mark.

"We observed that when vision was restored, corrective adjustments were made as the foot came close to the target," Reynolds told LiveScience.

The possible consequence of a misstep is, of course, a fall. The scientists hope that by learning how basic walking is controlled, they can better understand what goes wrong in people.

"It is important to know how healthy people control foot placement, so that we may understand what goes wrong in people who have neurological disorders which may cause them to fall," Reynolds said.

The researchers are now working on determining the extent to which one can alter foot placement during a step, which may have relevance for obstacle avoidance, Reynolds explained.

The study was detailed in the December issue of the Journal of Physiology.

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