UBC ‘body-swap’ robot helps reveal how the brain keeps us upright

What if a robot could show us how the brain keeps us balanced? UBC scientists built one – and their discovery could help shape new ways to reduce fall risk for millions of people.

A towering ‘body-swap’ robot built by University of British Columbia researchers is giving scientists an unprecedented look at how the brain keeps us standing—a skill we barely notice until affected by age or disease.

Their findings, published today in Science Robotics with collaborators at Erasmus Medical Clinic, reveal that to stay balanced, the brain treats delays in sensory feedback almost the same way it handles changes in body mechanics. In other words, when it comes to balance, our sense of space and time appears to work from the same playbook.

“What’s exciting is that this opens the door to new practical applications,” said Dr. Jean-Sébastien Blouin, senior author and professor in UBC’s School of Kinesiology. “If we understand how the brain copes with delays and mechanical changes, we can design assistive devices or rehab strategies for older adults and even build robots that move more like us.”

The physics of a body swap

Standing upright is one of the brain’s most complex jobs. Every second it coordinates signals from the eyes, inner ears and feet to assess, predict and correct movements against gravity.

Even in healthy adults, balance signals don’t arrive instantly. There’s a natural lag as information travels to the brain and back to muscles. Aging or conditions like diabetic neuropathy and multiple sclerosis can worsen these delays, making falls more likely.

“Imagine steering a car when the wheel responds half a second late,” said Dr. Blouin.

Studying how the brain handles these delays has been nearly impossible—you can’t easily slow nerve signals or change someone’s body mechanics while they’re standing.

But the UBC robotic platform can, using a clever trick of physics to change how your body feels.

Participants stand on force plates attached to a backboard driven by high-precision motors. The system reproduces the main forces that govern upright stance: gravity pulling down, inertia resisting movement, and viscosity, the damping effect of muscles and joints that stop a lean from turning into a fall, for example.

In real time, the robot tweaks these forces. Increasing inertia makes the body feel heavier; higher viscosity acts like a brake, while negative viscosity does the opposite—like someone giving you a push so you fall faster in the direction you’re moving.

The robot can also add a short delay—about 200 milliseconds, roughly the blink of an eye—by briefly holding your body still after you try to move. That pause makes your response feel late, just like when nerve signals slow down, so your balance corrections come after you expect them.

“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.”

Three tests, one big find

The team ran three experiments.

First, they introduced a delay and watched 20 participants sway dramatically, often exceeding the system’s virtual limits, or the point where they’d have fallen in real life.

Next, they tested whether changing body properties could mimic the same effect. Lowering inertia or applying negative viscosity made participants just as unstable, and many said it felt similar to balancing with the delay—evidence that the brain interprets space and time in overlapping ways.

Finally, they flipped the problem: could adjusting body mechanics help compensate for delays? They brought in ten new participants who had never experienced the machine, and subjected them to a delay. When the robot boosted inertia and viscosity, participants instinctively regained control. Their sway dropped by as much as 80 percent and most did not fall.

“We were amazed that adding inertia and viscosity could partly cancel the instability caused by late feedback,” said lead author Paul Belzner, a former UBC kinesiology master’s student.

What this means for preventing falls

Falls are one of the most serious health risks for older adults, often robbing people of their independence and costing Canada’s health-care system over $5 billion each year.

When nerve signals slow, there’s no simple way to speed them up. “That’s what makes our findings so exciting,” said Dr. Blouin. “It suggests we can help in another way—by giving the body a small mechanical boost that makes balance easier for the brain.”

Future tools could include wearables that add gentle resistance when someone starts to sway or robotic trainers that teach patients to adapt to slower feedback. The same insights could even help engineers design steadier humanoid robots.

The UBC robot will soon move into UBC’s new Gateway health building, where researchers at the UBC Balance and Falls Research Centre, School of Kinesiology, School of Biomedical Engineering, and Centre for Aging SMART will use it to advance fall-prevention technologies and support healthier aging.

The robot was engineered and validated at the UBC School of Kinesiology in the faculty of education with funding from the Natural Sciences and Engineering Research Council of Canada and the UBC School of Kinesiology Equipment and Research Accelerator Fund.

Interview languages: Blouin (English, French), Bilzner (English)