Step by Step

Lena Huang (SAR’17) hopes her research will inform future studies on the benefits of retraining patients in walking after weight loss. Photo by Dana J. Quigley

For people struggling with obesity, everyday movements like walking and stepping onto a curb are more than laborious. They can be treacherous, posing the risk of falling. Surgical weight loss can make walking easier, but it doesn’t necessarily cut the risk of taking a tumble.

It seems counterintuitive, but researchers have an explanation: those who have undergone bariatric surgery often retain atypical walking habits they developed to accommodate their weight. Individuals with obesity must exert more energy to maintain their balance while walking than those with average body mass indices (BMIs). And when they step over an obstacle, their supporting leg uses extra energy to keep the body balanced. They adapt their gait—by taking shorter, slower steps, for example—to avoid expending excess energy, but such atypical walking patterns lead to a higher risk of falling. There is no targeted intervention to help people learn to adjust their gait following bariatric surgery.

Lena Huang (SAR’17), a Boston University College of Health & Rehabilitation Sciences: Sargent College (SAR) human physiology and premed student, is studying the body’s movements to determine the variables contributing to fall risk. While previous experiments have been conducted in the lab and on flat ground, Huang is researching the risk of falling after bariatric surgery in a natural environment where obstacles abound: the home. With new technology, she’s gathering data that could lead to more targeted therapies and a reduced risk of falling. “We’re trying to address something not very well known in terms of how to help these clients move safely during their everyday activities,” says Huang’s mentor, Simone V. Gill, a Sargent assistant professor of occupational therapy and director of the Sargent Motor Development Lab.

With funding from BU’s Undergraduate Research Opportunities Program (UROP), Huang is conducting a study for which she aims to engage 20 participants, 10 of whom have undergone bariatric surgery and 10 who have not. The work begins in the lab, where she wraps electronic LEGSys sensors around each participant’s legs, just above the ankle and knee. She secures another sensor to the small of the participant’s back. The participants complete five laps on a runway and step over one of three obstacles—a limbo-style pole at three different heights—introduced midway through each lap. Using Bluetooth technology, the sensors deliver real-time data about the individual’s stride length and width, as well as the number of steps per minute, providing a full picture of their gait and potential fall risk.

The participants continue the assessment at home using a PAMSys sensor, a small device worn around the neck for two consecutive days, except when showering or sleeping. A relatively new tool, the PAMSys sensor provides more realistic measures than when individuals perform specific tasks over a short, predetermined period of time in a lab.

For instance, PAMSys sensors track how individuals transition from standing to sitting. “Some might hold on to the armrest and slowly go down, where others might plop down,” explains Huang.

Her research could illuminate whether potential changes in center of mass or stride length and width associated with weight reduction are connected to postural instability. When one variable changes to an extreme, the other offers a counterbalance to prevent fall risk. For example, an individual’s center of mass is constantly shifting left to right and front to back when walking; if the body shifts a little too far from a normal range, the likelihood of falling increases

Huang intends for this research to inform future studies on the benefits of retraining patients in walking after weight loss and hopes it will lead to innovations that minimize fall risk. “Ideally, clinicians will be able to tailor interventions to the client,” Gill says. Such interventions could include prescribing activities for home practice while a wearable device communicates patients’ progress to their practitioners, who will help them adjust their movements.

Huang’s work earned her the Outstanding Student Researcher Award at the 2015 UROP Symposium. It has also provided her with a foundation for future research and her intended career as a doctor of family medicine. In particular, collaborating with experts, including physicians, statisticians, and biomedical engineers, has given her a deeper understanding of the connections among health disciplines.

Working with Gill, she’s learning how to conduct a study, from applying for grants and designing the protocol, to recruiting subjects and analyzing data. “UROP helped me see how research works and how to do it effectively,” she says. “It helped me see how everything works together.”