Research at the University of North Carolina shows lower-limb amputees could benefit from load-adaptive wearable robotics. While multiple studies examine the ways powered devices help amputees walk on level ground, few delve into the effects of real-world challenges such as carrying groceries. Andrea Brandt, a Ph.D. student in the NC State and University of North Carolina-Chapel Hill Joint Department of Biomedical Engineering, and her team set up experiments involving weighted backpacks. Five amputees using a typical powered knee prosthesis wore the backpacks to add 20 percent of their body weight. A motor in the prosthesis actuates the knee and a fixed ankle joint. The team programmed the devices with several power settings. On the normal setting, the users reported difficulties walking when carrying the added load. “Perceived exertion definitely increased, the device would hyperextend, and people relied more on their intact limb, which is already being overused,” Brandt said.

When the prosthesis setting was switched to load-bearing, study participants reported fewer problems walking on a treadmill while wearing the backpacks. Researchers found the amputees reported few problems with the devices at either setting when not carrying a backpack. “Carrying a load makes your muscles contract in different ways that aren’t being mimicked in prostheses today,” Brandt said. She said more study is needed into real-world tasks involving people wearing the devices.

What’s going on in the lab now? Brandt plans to study how to get more function out of powered prosthetic devices. The key is find the right parameters that control how the prostheses perform. By developing smart controllers that adapt the devices to everyday situations — such as carrying loads, walking on grass — amputees could return to activities they love, she said. The result also could potentially prevent secondary health issues such as osteoarthritis and back pain from overuse of intact limbs. Health Tech Insider earlier this month reported a Mayo Clinic study into the short-term costs and longtime health benefits of smart powered prosthetics.