An ingenious experiment using an adapted treadmill has shown that our brain seems to store patterns for the smooth movement of our legs independently for each leg, and for each direction of walking.
The study, devised by neuroscientists Julia Choi and Dr Amy Bastian, used a split-belt treadmill – a normal treadmill for walking but where each side can be programmed with its own speed and direction.
They asked 40 volunteers to walk on the treadmill while they varied the speed and direction of each belt. They then recorded the limb movements with sensors attached to key body positions.
They found that even for unnatural walking patterns, where the two belts were going in different directions at different speeds, participants quickly adapted so that they maintained smooth graceful walking patterns.
The researchers varied these patterns so that they could separate out the adaptation needed for each limb in different directions.
After the person had adapted to the new pattern, the researchers then asked participants to walk normally.
The participants walked with a limp, showing that the brain had adjusted existing walking patterns within a matter of minutes to allow for the new style of walking, and that this new pattern was stored and still in place, even to the point of slightly disrupting normal walking.
The best demonstration of this is a short video of the results produced by the research team.
Because this could be shown to occur separately for each leg and direction, it suggests that we don’t have a single ‘rhythm generator’ (known as a central pattern generator or CPG) for walking.
This could have important implications for treating people who have walking problems caused by brain damage that affects movement in one particular limb.