Research Frontiers: Back in Stride -- Innovative Treadmill Study Helps Restore Walk Patterns

Martie
Callaghan

Motion Analysis LaboratoryYou're waiting at the airport for your best friend to arrive. It's been several years since you last saw each other. A figure emerges from the throng of travelers, and as he walks quickly toward you, you recognize your friend right away by his long, loping stride. The way he walks, or his gait, is a very complex characteristic that, like a fingerprint, is unique to every person.

A person's gait is typically driven by a combination of genetic and neurological factors, but sometimes, a traumatic event, such as a stroke or other brain injury can cause a problem with the walk pattern.

Researchers at the Kennedy Krieger Institute's Motion Analysis Laboratory are using an unusual split-belt treadmill to help bring back the walk pattern in children with one-sided brain damage and also in a select group who have undergone a hemispherectomy, a surgery in which an entire lobe of the brain is removed. This treadmill was specially designed to independently control how each leg moves, making one leg walk slower or faster than the other.

"You do it all the time!" says Amy Bastian, PhD. "When you walk in a circle, the leg on the outside has to take a bigger step than the leg on the inside. It's more novel to have a difference in leg speed when walking in a straight line, but very easy for people to do. They immediately produce a pattern that keeps them on the treadmill without falling."

To create a baseline, studies were first performed on people with normal walking patterns, using the treadmill to move their legs at different speeds and in opposite directions. Within a few minutes the subjects were trained to walk with a lurch. No matter how hard they tried to walk normally at the end of the session, they were unable to do so until their nervous system automatically recalibrated, usually within about 10 minutes.

Just as a limp is trained into a person, a limp can be trained out of a person.

The first step was to determine if the brain could learn a new pattern on a short time scale and then to see how the damage to different parts of the brain affected this ability.

"We now know that you need the cerebellum more than the cerebrum to adapt walking in this way," Dr. Bastian says. "That is good because most often, damage occurs in the cerebrum, as with a stroke or a hemispherectomy, and it is that damage that causes the limp."

The training session is somewhat counterintuitive to traditional rehabilitation programs where patients are told to think about what they're doing. Walking on the split-belt treadmill is more easily accomplished if the patient is distracted or thinking about something else. The lower, less conscious control networks take over and the new patterns are learned involuntarily. The challenge is to make the improved walking permanent. As with any activity, walking on the treadmill for 10 minutes does not cause the brain to adopt the new motor pattern.

"The nervous system doesn't want to change its circuitry for something that it will experience only once," explains Dr. Bastian, "but if the pattern is experienced repeatedly, over and over, then the brain is better served by learning that new pattern because it will need to use it."

A new, long-term study is underway to teach people a new walking pattern that they will use all the time - not just when they are on the treadmill.

"We have many studies going on in the Motion Analysis Lab, uncovering basic mechanisms," Dr. Bastian says. "We think that is a critical process that must precede treating patients. This particular study is very exciting because it has reached the point where we can start to test a treatment."