The treadmill hums as bright lights from a wraparound virtual reality screen flicker on the walls, casting moving shadows across Elizabeth Christopher’s face. Small silver sensors dot her joints, measuring her movement. And behind a computer monitor nearby sits Jason Franz, a professor of biomedical engineering at UNC-Chapel Hill.
Franz is the director of the Applied Biomechanics Lab in the Lampe Joint Department of Biomedical Engineering at UNC-Chapel Hill and NC State University. His mission is simple: find solutions to help people age gracefully. In a world where nearly one in five Americans will be over 65 by 2030, that goal is more urgent than ever.
Franz has spent the past two decades investigating how age-related changes in muscle strength, joint flexibility, and balance impact mobility, especially as people enter their later years. Falls among older adults are the leading cause of injury and death, yet they are often preventable with the right interventions.
“I am 61, almost 62 years old,” Christopher, a participant in one of Franz’s studies, shares. “I’m much more aware of the fear of falling. I’m much more aware of trying to challenge myself in different ways to stay active both mentally and physically. It’s part of getting older and not having the flexibility [or] the stability we take for granted until it’s not there anymore.”
In Franz’s state-of-the-art lab, participants walk, move, and even slip — all under carefully controlled scenarios designed to simulate the unpredictable nature of daily life.
“Young people fall all the time,” he says. “The difference between a fall that you might see in a toddler and a fall that we view in our older community is the consequences. The risk of fracture, risk of injury, and the economic costs of a fall can be devastating.”
Impact Report
Each year, one in four older adults report falling, which is the leading cause of injury in the aging population. Nearly 20% of North Carolina’s population is above 65 years old, making aging a critical research focus for the state.
Since 2003, the Lampe Joint Department of Biomedical Engineering at UNC-Chapel Hill and NC State University has been a significant contributor to education and research on important topics like aging. With approximately 600 students and 50 faculty members, the department boasts a wide variety of expertise and impact.
Mapping mechanics
Growing up, Franz spent his summers on the eastern shore of Maryland with his grandfather. Over time, he saw the toll that aging could take on a man that had once been active.
“I watched him go from being the most physically capable person that I knew to becoming frail,” Franz says. “He had difficulty with walking and standing up out of a chair and eventually started falling. And it struck me that we could probably do better as engineers in coming up with solutions to meet the needs of those in our rapidly aging communities.”
His lab’s research has led to important findings about how aging impacts walking and mobility. Older adults experience changes in how the body moves and how the nervous system controls movement — changes that can make someone more likely to feel tired or to fall.
One key finding is that older adults often exhibit less vigor when pushing off the ground, which leads to shorter, shuffling steps and slower walking speeds. This change is primarily due to muscle redistribution. Older adults rely more on their hip and thigh muscles, which cost us more energy than the ankle muscles used by younger adults.
Franz’s team also found that the Achilles tendon, which plays a critical role in pushing off the ground during walking, loses its stiffness with age. As the tendon loosens, it doesn’t stretch and recoil as effectively. This change means the muscles attached to it, mainly those in the calf, must contract more to produce the same movement, leading to higher muscle activation, increased energy consumption, and more fatigue.
This makes older adults more vulnerable to losing their balance, especially during longer walks or on uneven terrain. The lab’s work is focused on developing interventions to mitigate this.
They use tools like wearable sensors, 3D motion capture cameras, force sensors on a treadmill, and video X-ray to provide real-time biofeedback or inform assistive technologies. That data can help individuals adjust their gait and walking patterns, making them more dynamic and less prone to falls.
Lasting balance
Franz meets with study participants, physical therapists, and members of the older population regularly to ensure his work is having the impact he intends and to address their needs directly.
“We want to have genuine impact when we’re doing a study, and the only way we can do that is by speaking the language of the individuals who might make use of the work we’re doing,” he explains.
“I find that I do kind of trip on my foot every now and then just walking outside,” Christopher says. “My mother has experienced a couple of falls, and she’s 90 now. And so I want to avoid that in my future.
Franz also prioritizes mentoring and teaching in his lab. The curiosity and tenacity that postdoctoral scholars, graduate students, and undergraduate researchers bring to his research gives him hope for the future of the field.
“As we advocate for the fields of rehabilitation engineering and biomechanics more broadly, I would love to see a greater understanding of the impact we’re having on the world,” he says.