People learn to use robotic leg prostheses but misjudge their gait ^{CEFR B2}

Understanding how the body represents movement is important for teaching physical skills. A new study, led by Helen Huang, a professor of biomedical engineering at North Carolina State University and the University of North Carolina at Chapel Hill, is the first to examine how people incorporate a lower-limb robotic prosthetic into their body image and how that changes with practice. The researchers recruited nine able-bodied participants for a four-day experiment. Each person walked on a treadmill while wearing the robotic prosthetic with the knee fixed at a right angle and was instructed to walk as quickly as possible without touching the handrails.

After each practice session, participants viewed computer animations showing a range of biomechanical walking gaits and selected the gait that best matched their recent performance with the device. Objective performance improved significantly over the four days, but subjective perception diverged from reality: initially participants judged their gait as more off-balance and stilted than it actually was, while by the end they judged it as more fluid and natural than it actually was. In short, confidence grew but accuracy did not.

The study found that participants based their judgements mainly on torso position and rarely emphasised the behaviour of the prosthetic itself. The authors suggest this focus may stem from limited direct feedback about the device and the fact that users usually cannot see themselves while walking. They propose that giving visual or other feedback could help calibrate body image and gait during training, and warn that overconfidence may reduce users’ effort to improve. The paper appears in PNAS Nexus and the work was supported by the National Institutes of Health and the National Science Foundation. Source: NC State.