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A new framework for studying stability during walking — ScienceDaily

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Falls are a serious public health problem, resulting in tens of thousands of deaths each year and racking up billions of dollars in healthcare costs. Although there has been extensive research into the biomechanics of falls, most current approaches study how the legs, joints, and muscles act separately to respond, rather than as a system. The ability to measure how these different levels relate to each other could paint a much clearer picture of why someone falls and precisely how their body compensates. Until recently, however, an integrated measurement approach was elusive.

In recently published research, Pawel Golyski and his Ph.D. Advisor Greg Sawicki, associate professor of mechanical engineering and biological sciences at the Georgia Institute of Technology, is studying whether mechanical energy can be used as a “common currency” to measure how humans use the lower limbs to stabilize themselves during walking . Their research, published in the Royal Society Interface Journal, lays the groundwork for using mechanical energetics to understand the roles of joints and muscles during unsteady locomotion. The article also contributed to Golyski’s selection as this year’s recipient of the American Society of Biomechanics (ASB) Predoctoral Achievement Award.

Golyski, a graduate member of Sawicki’s Wearable Robotics Physiology (PoWeR) Laboratory, previously worked as a research scientist with lower limb amputees at Walter Reed National Military Medical Center. For her graduate studies at Georgia Tech, her goal was to develop an understanding of how devices and the human body work together, particularly at the intersection of three elements: muscle mechanics, wearable exoskeletons, and stability during motion. walking.

Each of the three elements is related to the others. Exoskeletons affect a person’s stability while affecting the functioning of their muscles, and vice versa. But examining how muscles interact with exoskeletons and affect stability is an interesting challenge, Golyski says. Because, although one can observe how muscle dynamics change with the use of an exoskeleton, the relationship between these changes and stability is not understood. To understand how the three pillars work together to help humans compensate during a fall, Golyski and Sawicki needed to come up with a new framework for measuring stability.

Energy accountants

Researchers knew that for a person walking at a constant speed on flat ground, the net mechanical energy of the person and each leg in one stride – from the heel strike of one leg to the next heel strike of that same leg – is zero. They also knew that energy should equal mechanical energy at all levels of description of the leg, especially the joints and muscles.

“The idea is that if we can relate stability to a demand for energy, then we can become accountants and track how energy – our currency – changes at the level of the person, the muscle and the exoskeleton” , said Golyski. “It provides a really powerful framework for linking these three areas.”

Golyski and Sawicki designed an experiment with a person walking on a treadmill. Using a split-belt treadmill, they applied short, quick disturbances, called disturbances, in the form of belt speed increases on one leg while walking. The aim was to inject or extract energy during a stride, in order to then be able to measure the evolution of the energies of the person’s legs and joints.

For the experiment, they used Georgia Tech’s CAREN (Computer Assisted Rehabilitation Environment) – an integrated system used to study stability during movement. It features cameras mounted above a treadmill to track a person’s movement using motion capture markers attached to the person. Using an algorithm designed by Golyski, Sawicki, PoWeR lab Ph.D. student Jennifer Leestma, and high school mentee Esmeralda Vazquez, CAREN can run perturbations based on a person’s movements, allowing researchers to initiate disturbances at specific times in the gait cycle. By combining the force of the treadmill with positional data collected by CAREN, Golyski and Sawicki can calculate energy changes in a person’s individual joints.

Their new framework could help determine which part of a person’s body is dealing with destabilizing energy responses, indicating specific muscles or joints to target with rehabilitation therapy. It could also open the door to advanced exoskeletons and prosthetics that target specific joints to restore stabilizing responses in people with balance disorders.

“The body of research that Pawel has done during his doctoral studies is simply impressive. He has innovated by developing new experimental techniques and a new device to assist the hip exoskeleton, by carrying out measurements new muscle imaging techniques and ultimately answering the question of how exoskeletons alter joint and muscle dynamics to influence the stability of human gait,” said Sawicki. “I was delighted that Pawel’s outstanding contributions as a scientist-engineer have been recognized by the ASB, and I am even more delighted that he is returning to Walter Reed – his dream job – to apply his new skills to help people from here. until there.”

This summer, as part of this recognition, Golyski will deliver a research lecture at an awards session at the North American Biomechanics Congress in Ottawa, Ontario. He will also graduate from Georgia Tech and return to working with veterans and active service members at Walter Reed.

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Material provided by Georgia Institute of Technology. Original written by Catherine Barzler. Note: Content may be edited for style and length.