Biomechanical engineer’s app can help people stay mobile longer.

Scott Delp became fascinated by the differences in human performance as a college athlete after a serious sports injury. Magnetic resonance imaging was not yet widely available, leaving doctors unclear about how best to treat him. Delp wondered why some people are able to hone their bodies to win Olympic medals, while others struggled to walk.

As an undergraduate engineer at Colorado State University, Delp realized how little was known about the biomechanics of the body. In 1985, he came to Stanford for his graduate studies and began to focus on how to apply principles of mechanical engineering to medicine. Working with clinicians at Lucile Packard Children’s Hospital Stanford and advisers in mechanical engineering, neuroscience, surgery and computer science, Delp trained in the design division of the Department of Mechanical Engineering, which later became Stanford’s renowned Hasso Plattner Institute of Design, known as d.school.  

“Everything we were designing was from an engineering point of view and on a computer,” Delp says of his early research. “But medicine was being practiced by watching people move and trying to figure out this extraordinarily complicated system by just thinking about it.” 

Delp decided that, just as mechanical engineers design satellites, they should develop surgical procedures and medical interventions using computer-generated simulations. That would require what he calls “intensive cross-training” in engineering, computation, design, biology and medicine, a high bar given the complexity of those disciplines. That approach has made Delp a leading figure in modern bioengineering, a field with profound implications for extending healthspan and changing the future of aging. 

As the founding chair of Stanford’s bioengineering department and developer of the widely used OpenSim software, an open-source platform that enables engineers to build, exchange, test and improve musculoskeletal simulations, Delp has helped change how human movement is modeled to treat disabilities for people of all ages. He also has enabled a global collaboration around the science of human movement. “Keeping people moving is the most important medicine we have to maintain our healthspan,” he says.

Movement patterns — being able to walk and talk — are a window into cognitive and mental health as well as a key indicator of aging.

Indeed, Delp sees movement as a key longevity biomarker. Movement patterns — being able to walk and talk — are a window into cognitive and mental health as well as a key indicator of aging. “If I’m walking with an older person, they’re holding my arm,” says Scott by way of example. “We’re walking along. They want to talk to me. So they have to do dual tasks now. Some may stop walking because the cognitive task and the physical task leads to overload.”

For these reasons, accessing gait, balance and other basic aspects of human movement should be accessible and affordable, argues Delp. Which is why his lab recently developed OpenCap, a smartphone-based system that brings laboratory-quality biomechanical analysis into clinics, gyms or even someone’s home.

The core innovation of OpenCap is its technological mashup. It uses videos from just two smartphones to capture human movement and then applies AI- and physics-based modeling to extract detailed biomechanical data, including joint angles, muscle forces and movement patterns. The data quality is comparable to what you would get from motion capture labs with specialized cameras and force plates. The technology helps with diagnosis and treatment — for example, revealing someone’s risk for ACL injuries or for gait issues that relate to osteoarthritis and pain and could indicate early signs of neuromuscular deterioration from diseases like Parkinson’s and MS. It’s also being used in clinical trials to determine the effectiveness of certain treatments. 

“The OpenCap software allows us to democratize access to very sophisticated motion analysis that we’ve been able to do in my laboratory for 30 years,” Delp says. “We developed the software because we wanted to be able to make assessments rapidly, inexpensively. Instead of 10 participants, we can study 1,000.”

OpenCap is a project of the Wu Tsai Human Performance Alliance, which Delp directs. The research coalition of more than 100 institutions now has access to the app, which like OpenSim is open source. “It’s better science,” Delp says of the approach. “We support this for thousands of research groups around the world.”

Next on Delp’s research agenda is the mind-body connection. He notes that how a person is moving reveals a lot about their mind. “The ability to quantitatively assess motion can give us a window not just into physical ability but also into mental health and cognitive ability,” he says. “This interface is fascinating and untapped and important to understanding thriving in old age.”

Liz Wollman is a veteran business editor who previously covered Silicon Valley and the tech industry at The Wall Street Journal.