These Pitt researchers are making steady progress toward a confident gait

A host of changes come with aging, from brittle bones to worsening memory to failing eyesight. People also may experience changes in the way they walk, developing asymmetric gait patterns, though they may not notice the change. It's a problem that often affects people with certain conditions, including stroke.

Researchers from Pitt's Swanson School of Engineering and the Catholic University of Uruguay are working on a series of studies to better understand how people perceive changes in their environment as they walk. The research team, led by Associate Professor of Bioengineering Gelsy Torres-Oviedo, aims to use its results to boost early detection of some conditions and, ultimately, to help people with gait asymmetries walk out into the world confidently and safely.

Their most recent work was published in eNeuro, a journal of the Society for Neuroscience.

For this study, the team sought to determine the smallest change in speed that participants could detect. It turns out, people are more sensitive to change than previously thought.

To figure this out, the researchers used a treadmill with two belts connected to different motors. Research participants - neurologically healthy adults between 19 and 40 years old - walked with one foot on each belt. After a period of normal walking, with both belts going the same speed, researchers increased the speed of one belt and slowed down the other by the same amount.

"When the speed difference was introduced, participants had to quickly identify which leg was moving slower," Torres-Oviedo said. "We found that people could detect these differences even when they were quite small, much smaller than we previously thought possible during walking."

When the speed changed on the treadmill, participants indicated which leg they thought was moving slower by clicking a button. It's this perception of change that the researchers were after.

"We found that people were able to tell when there was a 50 millimeter-per-second difference between their legs with 75% accuracy," said lead author Marcela Gonzalez-Rubio, a PhD candidate in Torres-Oviedo's lab. That's about two inches. Previously, researchers believed people could only sense changes of 5 inches per second.

"This is the first time we've asked, 'How are they sensing?'" said Pablo A. Iturralde, professor of electrical engineering at Catholic University of Uruguay. "This was a big unknown to us"

When Iturralde began studying people on the treadmill as a PhD student in Torres-Oviedo's lab, he said, "We knew what the muscles were doing, we knew how the legs were moving, but we did not know what people were perceiving when this was happening."

Their latest finding has real-life implications. "It helps us to be able to accurately measure when someone has a sensory deficit in a way that is relevant to how they respond to changes in their environment," Iturralde said. It may also help doctors better predict how a patient will be impacted after having a stroke or traumatic injury.

And watching changes in sensory perception could also help when it comes to evaluating how well someone is or isn't responding to rehabilitation, Torres-Oviedo said.

As the team continues to build this body of research, they are developing a framework to better understand the roles people's senses - and sensory deficits - play in navigating their environments. For example, previous work showed, among other things, people have problems adjusting the way they walk in new environments.

The researchers wondered if people become less steady as they age because they have difficulty sensing their environment and so didn't trust themselves to make any corrections to their gait. "Now we can measure people's sensation as they get older and ask that question," Torres-Oviedo said.

Once their questions are answered, the research team will be able to take its next step, working toward solutions that keep people steady on their feet.