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 intricate 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 quicker, endure more pain, and face higher fall risks.
Innovative Hip Exoskeleton Offers Relief
Engineers at the University of Utah’s John and Marcia Price College of Engineering, collaborating with the College of Health, have developed a portable, lightweight hip exoskeleton. This 5.5-pound device, worn around the hips and strapped to the thighs, uses battery-powered motors to assist leg movement with each step, promoting a more efficient gait. Custom-tuned motor assistance on each side syncs in real time via an intelligent control system, delivering precise boosts for hip lift and push-off.
“Improving quality of life after a stroke remains one of healthcare’s greatest challenges,” stated senior author Tommaso Lenzi, associate professor in the Department of Mechanical Engineering. “Robotics now demonstrates measurable benefits in this area.”
Why Hip Assistance Beats Ankle Exoskeletons
Previous powered exoskeletons targeted foot drop and ankle propulsion issues but failed to lower walking energy costs for stroke patients. “Portable ankle exoskeletons did not reduce energy demands, prompting a new strategy,” explained lead author Kai Pruyn, a graduate student in Lenzi’s HGN Lab for Bionic Engineering. “Patients with weak ankles often overcompensate with hips, wasting energy. Our fully portable hip exoskeleton addresses this directly. Positioned near the center of mass, it achieves high power with low weight and torque needs compared to ankle versions.”
The lab, known for wearable robotics like the Utah Bionic Leg—named a top 2023 invention by Time magazine—is the first to prove hip exoskeletons boost efficiency in hemiparesis patients, building on prior healthy-user studies.
Study Delivers Compelling Results
Researchers analyzed gait in seven hemiparesis patients using motion-capture on an instrumented treadmill, both with and without the exoskeleton. Equipment measured caloric expenditure to compute metabolic costs. The device offloaded nearly 30% of hip joint work, slashing overall walking energy by 18%—equivalent to removing a 30-pound backpack for healthy walkers.
“For those with hemiparesis, this represents a transformative change,” noted co-author Bo Foreman, professor of Physical Therapy & Athletic Training.
Participants reported enhanced mobility. “At first, I couldn’t move my leg,” shared stroke survivor Lidia. “Now with the device, it’s much improved.” Her husband Marcellus added, “The exoskeleton handled some movement for her. The more she used it, the better she performed without it.”
Path Forward to Everyday Use
Next, the team aims to validate safety and efficacy in home and daily settings, refining mechanics and controls for diverse activities. Partnerships with prosthetics and orthotics experts will commercialize the technology.
“We strive to ensure a stroke does not limit a person’s mobility or lifestyle,” Lenzi affirmed. Findings appear in Nature Communications (DOI: 10.1038/s41467-026-69580-0).
