December 2005 — Placing your foot accurately
is a complicated process. If something moves where you plan to place
your foot then you can adjust your step while your foot is swinging
through. Experts thought previously that if nothing changed in the
path, or in your plans, then the place where your foot will land is
fixed before it even leaves the ground. In this case, you would make no
use of immediate visual information during each step.
Researchers monitored the accuracy with which subjects could step
onto a target. In 50% of the attempts they blocked subjects’ vision
just at the point when they were lifting their foot off the ground. On
the occasions when vision was blocked, the subjects were less able to
step accurately on the target.
"Because vision was blocked only after the foot had left the floor,
this research shows that we use visual information to adjust our
footfall while our foot is moving forwards — it is not simply
predetermined at the beginning of the step," says Dr Raymond Reynolds,
who along with Dr Brian Day conducted the work at the Institute of
Neurology, Queen Square, London. The research is published this week in
the Journal of Physiology.
This research models the sort of situation people encounter when
rambling over rough terrain, where they need to accurately place their
feet on well defined targets. Getting it right may avoid your slipping
or twisting an ankle. "This visual guidance mechanism could also help
gymnasts on the beam, or acrobat walkers on a tightrope, as in these
situations accurate foot placement becomes crucial," says Reynolds.
Source : Blackwell Publishing Ltd.