Author Archives: Jason Franz

A team of faculty from the Lampe Joint Department of Biomedical Engineering at the University of North Carolina at Chapel Hill and NC State University, the Department of Orthopaedics at the UNC School of Medicine, and the University of Delaware received a $3M R01 grant from the National Institutes of Health (NIH) to explore Achilles subtendon relationships and their role in treatment outcomes in patients with Achilles tendinopathy.

The project will be led by Stephanie Cone, assistant professor in Biomedical Engineering at the University of Delaware and Jason Franz, professor in the Lampe Joint Department. Other project contributors include Geoffrey Handsfield, assistant professor in biomedical engineering and orthopaedics at UNC-Chapel Hill, along with Karin Silbernagel, professor of physical therapy at the University of Delaware.

Achilles tendinopathy is a painful and debilitating condition that results in inflammation, stiffness and difficulty walking. Exercise therapy is a gold standard treatment of the condition, but has a high recurrence rate in nearly half of all patients with this diagnosis. The Achilles tendon connects the heel to three separate muscles in an anatomical arrangement that varies between people, resulting in a complex anatomy that may lead to this inconsistency in success rates with current treatment.

To meet this challenge, the research team will integrate biomechanical sensors and medical imaging to develop models and enhance the understanding of anatomic variability between individuals. Through this research opportunity, the researchers’ insights and discoveries will guide future personalized clinical interventions to better support patients with this painful condition.

FROM UNC RESEARCH STORIES

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.”

 

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.

 

 

We are thrilled to congratulate Aubrey Gray for successfully defending her PhD dissertation, titled “Mechanical leverage of the foot and ankle: aging, balance, and the future of super shoes”. We also thank the wonderful support of her committee members, Jacque Cole (UNC/NC State), Kate Saul (NC State), Eric Ryan (UNC), and Kota Takahashi (Utah). Fantastic job, Aubrey!

Congratulations to 4th-year PhD candidate Emily Eichenlaub for receiving a 2024/2025 Award for Research Achievement from the Lampe Joint Department of Biomedical Engineering. The awards committee noted Emily’s NIH Fellowship “The Proactive and Reactive Neuromechanics of Instability in Aging and Dementia with Lewy Bodies”, industry internship experience in wearable sensing and movement biomechanics, and impressive scholarship and productivity as reasons for her selection.

An interdisciplinary team spanning Biomedical Engineering, Exercise and Sports Science, Biostatistics and the Thurston Arthritis Research Center has received a new 5-year, $3M R01 Grant from the National Institutes of Health titled “Discovering the Mechanisms Linking Gait to Osteoarthritis Onset and Progression.”

The project will be led by Co-Principal Investigators Dr. Jason Franz (Associate Professor in BME) and Dr. Brian Pietrosimone (Professor in Exercise and Sport Science) and will see pivotal contributions from BME Associate Professors Dr. Brian Diekman and Dr. David Lalush as well as from Dr. Todd Schwartz (Professor of Biostatistics) and Dr. Lara Longobardi (Associate Professor of Medicine).

Together, the research team will investigate the underlying mechanistic pathway to explain how aberrant knee joint loading in walking alters the mechanical, biophysical and biological properties of tibiofemoral articular cartilage in individuals at risk for knee osteoarthritis. The researchers noted “Establishing this mechanistic pathway is the single most important milestone toward advancing precision gait retraining as an effective strategy for preventing knee osteoarthritis.”

From the UNC/NC State Joint BME News announcements: https://bme.unc.edu/2024/01/dr-jason-franz-receives-two-awards-to-accelerate-wearable-sensing-to-optimize-knee-joint-health/

BME Associate Professor Dr. Jason Franz has established a highly productive and collaborative line of research that integrates wearable sensing and machine learning for precision rehabilitation of individuals with knee osteoarthritis. That research, in close partnership with Dr. Brian Pietrosimone from the UNC Department of Exercise and Sports Science, was recently recognized with two awards to accelerate their path from scientific discovery to commercialization and genuine translational impact.

The first, a 2-year $110k translational research grant from the North Carolina Biotechnology Center, will generate patient data to demonstrate proof-of-concept and feasibility of a novel wearable sensing and machine learning prediction technology for detecting, treating and monitoring aberrant forces during walking relevant to the onset and progression of knee osteoarthritis.

The second, a $50k commercialization grant from UNC Kickstart Venture Services, was awarded to VETTA Solutions – the start-up company inspired by these research discoveries and co-founded by Drs. Franz and Pietrosimone.

Commercialization and entrepreneurship are cornerstones of our mission here in BME, and we want to congratulate Dr. Franz and his entire team for their recent success.”

Exploring the Functional Boundaries and Metabolic Consequences of Triceps Surae Force-Length Relations during Walking (2021 Journal of Biomechanics Award Winner, American Society of Biomechanics)

Abstract. The relationship between individual muscle dynamics and whole-body metabolic cost is not well established. Here we use biofeedback to modulate triceps surae (TS) activity during walking. We hypothesized: (1) increased TS activity would increase metabolic cost via shorter muscle fascicle lengths and thus reduced force capacity and (2) decreased TS activity would decrease metabolic cost via longer muscle fascicle lengths and thus increased force capacity. 23 young adults walked on an instrumented treadmill at 1.25 m/s using electromyographic (EMG) biofeedback to match targets corresponding to ±20 and ±40% TS activity during push-off (late stance). B-mode ultrasound imaged the medial gastrocnemius (MG). Participants increased net metabolic power up to 85% and 21% when targeting increased and decreased TS activity, respectively (p < 0.001). At the instant of peak gastrocnemius force, MG fascicle length was 7% shorter (p < 0.001) and gastrocnemius force was 6% larger (p < 0.001) when targeting +40% TS activity. Fascicle length was 3% shorter (p = 0.004) and force was 7% lower (p = 0.004) when targeting -40% TS activity. Participants were unable to achieve decreased activation targets. MG fascicle length and activity mediated 11.7% (p = 0.036) and 57.2% (p = 0.006) of the changes in net metabolic power, respectively. MG force did not mediate changes in net metabolic power (p = 0.948). These findings suggest that changes in the functional operating length of muscle, induced by volitional changes in TS activity, mediate the metabolic cost of walking, relatively independently of force. Thus, shifts to shorter fascicle lengths may mediate activity-induced increases in metabolic cost.

Congratulations to all our lab members that attended and presented at the 2023 Annual Meeting of the American Society of Biomechanics!

 

Emily Eichenlaub, a third-year BME Ph.D. student, has received a National Research Service Award (NIH F31) from the National Institute of Aging. The award will fund her project titled “The Proactive and Reactive Neuromechanics of Instability in Aging and Dementia with Lewy Bodies.” The research will establish the effects of age and dementia on proactive and reactive neuromechanics underlying vulnerability to balance challenges. Emily will be sponsored by Dr. Jason Franz, Associate Professor in BME, and a mentoring committee that spans Engineering, Physical Therapy, Neurology and Biostatistics. Her research in the BME Applied Biomechanics Lab will pave the way for clinical translation in prescription of personalized interventions, wearable sensor monitoring to mitigate falls, and development of assistive devices with onboard monitoring of muscle neuromechanics to deliver assistance in the face of a balance challenge. Congratulations, Emily!!

 

The Metabolic Cost of Walking Balance Control and Adaptation in Young Adults.

Shawn Ahuja and Jason R. Franz

Background: Our aim was to quantify the role of metabolic energy cost in governing neuromuscular adaptation to prolonged exposure to optical flow walking balance perturbations in young adults. Research Question: We hypothesized that metabolic cost would increase at the onset of balance perturbations in a manner consistent with wider and shorter steps and increased step-to-step variability. We also hypothesized that metabolic cost would decrease with prolonged exposure in a manner consistent with a return of step width and step length to values seen during normal, unperturbed walking. Methods: Healthy young adults (n=18) walked on a treadmill while viewing a virtual hallway. Optical flow balance perturbations were introduced over a 10-minute interval during a 20-minute walking bout while measuring step kinematics and metabolic energy cost. For all outcome measures, we computed average values during the following four time periods of interest: Pre (minutes 3-5), Early Perturbation (minutes 5-7), Late Perturbation (minutes 13-15), and Post (minutes 18-20). A repeated-measures ANOVA tested for main effects of time, following by post-hoc pairwise comparisons. Results: With the onset of perturbations, participants walked with 3% shorter, 17% wider, and 53-73% more variable steps. These changes were accompanied by a significant 12% increase in net metabolic power compared to walking normally. With prolonged exposure to perturbations, step width and step length tended toward values seen during normal, unperturbed walking – changes accompanied by a 5% reduction in metabolic power (p-values≤0.05). Significance: Our study reveals that the adoption of generalized anticipatory control at the onset of optical flow balance perturbations and the subsequent shift to task-specific reactive control following prolonged exposure have meaningful metabolic consequences. Moreover, our findings suggest that metabolic energy cost may shape the strategies we use to adapt walking balance in response to perturbations.