University of Utah Exoskeleton Restores Walking Efficiency for Stroke Survivors
A fresh lightweight hip exoskeleton developed by researchers at the University of Utah is showing promising results in helping stroke survivors regain walking efficiency. The device, detailed in a recent study published in Nature Communications, reduces the metabolic cost of walking by nearly 20% for individuals with hemiparesis – a condition affecting motor control, muscle weakness, and spasticity on one side of the body.
Understanding Hemiparesis and its Impact
Hemiparesis affects approximately 80% of stroke survivors and is a leading cause of disability in the United States. Walking, while seemingly simple, requires complex biomechanics. Individuals with hemiparesis often expend 60% more energy when walking compared to those with a healthy gait, leading to slower speeds, reduced endurance, pain, and an increased risk of falls. This is given that even a small loss of strength on one side necessitates increased effort from the other side to compensate.
How the Exoskeleton Works
The University of Utah’s exoskeleton is a 5.5-pound device worn around the hips and secured to the thighs. Battery-powered motors assist leg movement with each step, promoting a more efficient gait. Crucially, the level of assistance is custom-tuned for each user, and an intelligent control system provides a boost precisely when the hip needs support for lifting or pushing off.
“Improving quality of life after a stroke is one of the biggest unmet challenges in healthcare today,” says Tommaso Lenzi, associate professor in the Department of Mechanical Engineering and the senior researcher on the study. “We’re now showing that robotics can make a measurable impact here.”
A Novel Approach to Exoskeleton Design
Previous exoskeleton designs often focused on assisting ankle mobility, addressing foot drop and impaired ankle propulsion. However, these portable ankle exoskeletons have not consistently reduced energy expenditure for stroke patients. The University of Utah team proposed a different strategy: a hip exoskeleton.
“Patients with ankle weakness often compensate with their hip joints, which requires extra energy,” explains Kai Pruyn, a graduate student in Lenzi’s HGN Lab for Bionic Engineering and lead author of the study. “Our goal was to develop a powerful and fully portable hip exoskeleton. Hip exoskeletons can similarly be extremely lightweight because they are worn closer to the user’s center of mass and have lower torque requirements compared to ankle exoskeletons. We found that the hip assistance effectively compensated for reduced ankle propulsion.”
Study Results and Impact
The study involved seven patients with hemiparesis who walked on an instrumented treadmill both with and without the exoskeleton. Researchers used motion-capture techniques and caloric expenditure measurements to assess the metabolic cost of walking. The results demonstrated that the exoskeleton offloaded nearly 30% of the work from the hip joints, resulting in an 18% decrease in the overall metabolic cost of walking.
“For a person with a healthy gait, this would be like taking off a 30-pound backpack,” says Bo Foreman, professor of Physical Therapy &. Athletic Training and a study co-author. “For someone with hemiparesis, that’s a life-changing difference.”
Participants in the study reported noticeable improvements in their mobility. Lidia, a stroke survivor who participated in the trial, shared, “In the beginning, I couldn’t move my leg. But with the device, it’s much better now.” Her husband, Marcellus, added that the exoskeleton seemed to facilitate movement, leading to improvements even when she wasn’t using the device.
Future Directions
The research team is now focused on ensuring the hip exoskeleton’s safety and effectiveness for everyday apply at home. This involves refining the device’s mechanics and controls to support a wider range of activities beyond walking. They are collaborating with experts in prosthetics and orthotics to translate this technology into a commercially available product.
“Our goal is to ensure that a stroke doesn’t define the limits of where a person can go or how they can live,” Lenzi concludes.
The study, “Portable hip exoskeleton improves walking economy for stroke survivors,” was published on February 14, 2026, in Nature Communications. Contributing researchers included Rosemarie Murray and Lukas Gabert. Funding was provided by the National Institutes of Health, National Institute for Occupational Safety and Health, and the National Science Foundation.