‘body Swap’ Robot Shows How Balance Slowly Declines With Age Due To Delayed Signals

UBC researchers have developed a life-sized ‘body swap’ robotic platform that is helping scientists understand how the brain keeps the body balanced.

The work offers a new way to study how we stay upright and may guide future fall-prevention tools for aging populations.

It suggests the brain treats delays in sensory feedback almost the same way it responds to changes in body mechanics.

How balance becomes harder

Maintaining balance looks effortless, but the brain constantly processes information from vision, the inner ear, and pressure sensors in the feet.

These signals help the body predict movement and correct posture. There is always a slight delay in the process.

As people age or live with neurological conditions such as multiple sclerosis or diabetic neuropathy, those delays grow longer, increasing fall risk.

“There’s no simple way to speed them up,” said Dr. Jean-Sébastien Blouin, senior author and professor in UBC’s School of Kinesiology.

“What’s exciting is that our finding suggests we can help in another way, by giving the body a small mechanical boost that makes balance easier for the brain.”

He said the work could support new rehab strategies, assistive technology, and improvements in humanoid robot balance.

Close-up of the robotic balance simulator’s foot plates. Credit – Sachi Wickramasinghe.

Until now, studying these delays in humans has been challenging because researchers could not artificially slow nerve signals or modify physical mechanics during standing.

The robotic platform solves that problem. Participants stand on force plates attached to a motorised backboard.

The system simulates and adjusts forces involved in standing, including inertia, gravity, and viscosity. Increasing inertia makes the body feel heavier.

Higher viscosity adds resistance. Negative viscosity has the opposite effect, speeding up a lean as if someone were being pushed.

The system can also add a short delay of about 200 milliseconds between a participant’s movement and the physical response of their body.

That delay creates the sensation of reacting too late, similar to what happens when sensory feedback slows.

“The robot lets us rewrite the rules your body normally plays by,” said Dr. Blouin. “In an instant, you’re moving under a completely different set of physical laws, almost like stepping into a different body.”

Researchers ran three controlled experiments. In the first, delayed feedback caused large sways and instability.

In the second, changes in inertia and viscosity created a similar instability, and participants reported that both situations felt alike.

In the final stage, the robot increased inertia and viscosity for a new group facing delayed feedback. Most regained stability quickly, and sway dropped by up to 80 percent.

“We were amazed that adding inertia and viscosity could partly cancel the instability caused by late feedback,” said lead author Paul Belzner.

looking ahead

Falls are a major health concern for older adults and cost Canada more than $5 billion every year.

The researchers believe the findings could eventually inform wearable devices that assist balance or robotic training systems that teach patients to adapt to slower neural feedback.

The team also expects their work to contribute to advances in humanoid robot design.

The platform will soon move into UBC’s new Gateway Health Building, where research on fall prevention, rehabilitation, and aging will continue.

The study is published in the journal Science Robotics.