Hemiparesis, a primary cause of disability in the United States, impairs motor control, weakens muscles, and causes spasticity on one side of the body. This condition affects 80% of stroke survivors, leading to reduced mobility and diminished quality of life for millions. Walking demands complex biomechanics, and even minor strength loss on one side forces compensatory efforts from the other, increasing energy expenditure by 60% compared to healthy individuals. Consequently, affected people experience slower speeds, fatigue, pain, and higher fall risks.
Breakthrough Hip Exoskeleton from University of Utah
Engineers at the University of Utah’s John and Marcia Price College of Engineering, in collaboration with the College of Health, have developed a portable hip exoskeleton that reduces walking energy needs by nearly 20% for stroke survivors with hemiparesis. The findings appear in Nature Communications (DOI: 10.1038/s41467-026-69580-0).
Weighing just 5.5 pounds, the device straps around the hips and thighs. Battery-powered motors assist leg movement with each step, promoting efficient gait. Custom-tuned assistance levels for each side sync in real time via an intelligent control system, delivering precise boosts during hip lift and push-off.
Improving quality of life after a stroke remains one of healthcare’s greatest challenges,” said senior author Tommaso Lenzi, associate professor in the Department of Mechanical Engineering. “Robotics now demonstrates measurable benefits here.”
Why Hip Assistance Outperforms Ankle Exoskeletons
Prior powered exoskeletons targeted ankle issues like foot drop and poor propulsion. However, lead author Kai Pruyn, a graduate student in Lenzi’s HGN Lab for Bionic Engineering, notes a key shift.
Portable ankle exoskeletons have not lowered walking energy for stroke patients, prompting our hip-focused approach,” Pruyn explained. “Weak ankles lead to hip compensation, demanding extra effort. Our fully portable hip exoskeleton addresses this directly. Positioned near the center of mass, it achieves lighter weight and lower torque needs than ankle versions, effectively countering reduced ankle propulsion.”
Lenzi’s team, known for the Utah Bionic Leg—a 2023 Time magazine top invention—leads in wearable robotics. While others showed hip exoskeletons boost efficiency in healthy users, this group first proves benefits for hemiparesis patients.
Study Results and Participant Feedback
Researchers analyzed seven hemiparesis patients walking on an instrumented treadmill, with and without the exoskeleton, using motion-capture and metabolic monitoring. The device offloaded 30% of hip joint work, slashing overall metabolic cost by 18%.
For healthy walkers, this equates to shedding a 30-pound backpack,” said co-author Bo Foreman, professor of Physical Therapy & Athletic Training. “For those with hemiparesis, it transforms daily life.”
Participants reported enhanced mobility. Stroke survivor Lidia shared, “At first, I couldn’t move my leg. With the device, it’s much better now.” Her husband Marcellus added, “The exoskeleton handled some movement for her. The more she used it, the stronger she became even without it.”
Future Developments
Next, the team refines the exoskeleton for home use and diverse activities, partnering with prosthetics experts for commercialization.
We aim to prevent strokes from limiting lives,” Lenzi stated.
