Body Image and Robotic Prosthetics: How Perception Shifts with Use

The way individuals perceive their own body movement is fundamental to learning physical skills, from athletics to dance. However, new research reveals this process differs significantly for those adapting to robotic prosthetic devices. A recent study from North Carolina State University and the University of North Carolina at Chapel Hill sheds light on how body image evolves as individuals learn to walk with prosthetic legs, and the implications for improving prosthetic training.

Initial Misconceptions and Shifting Perceptions

When individuals first commence using a prosthetic leg, they often overestimate how awkward their movements appear, according to Helen Huang, a professor of biomedical engineering and corresponding author of the study [1, 2]. Interestingly, as performance improves with practice, the misperception doesn’t disappear—it simply changes. Participants still struggle to accurately assess their gait, but their inaccuracies develop into different in nature.

“This is the first study to look at this phenomenon in people using lower-limb robotic prosthetics, and it raises a number of questions that should aid us improve people’s ability to walk with these devices,” says Huang [2].

The Role of Body Image

Everyone possesses a “body image”—an internal understanding of their body’s structure and how it moves. This understanding directly influences movement. When learning new skills, there’s often a disconnect between the perceived movement and the actual movement. Over time, these align with practice and performance improves. The study aimed to understand how individuals integrate a robotic prosthetic into their existing body image [1], [4].

Study Methodology and Findings

Researchers recruited nine able-bodied participants for the study. Over four days, participants walked on a treadmill using a robotic prosthetic attached to a leg bent at a 90-degree angle, aiming for the fastest possible speed without using handrails [2]. After each practice session, participants viewed computer animations of various walking gaits and selected the one that most closely matched their perceived movement with the prosthesis.

Initially, participants perceived their gait as more unbalanced and rigid than it actually was. By the finish of the four days, they felt their gait was smoother and more natural, though still inaccurate. While performance improved significantly, participants remained unable to accurately assess their movements, exhibiting greater confidence in their assessments [2].

The study revealed that participants primarily focused on the position of their torso when evaluating their gait, paying less attention to the behavior of the prosthetic device itself. This is likely due to a lack of direct feedback regarding the device’s movement [2].

Implications for Prosthetic Training

The findings suggest that providing visual or other forms of feedback about the prosthetic device’s behavior could help individuals calibrate their body image and improve gait during training. Addressing the overconfidence participants exhibited in their movement skills is as well crucial.

“If you already consider you’re doing great, you’re less likely to put in the operate necessary to get better—even if there is significant room for improvement,” Huang explains [2]. “We think it would be valuable to find a way to give people a more accurate assessment of how their body is really moving.”

Key Takeaways

• Individuals using robotic prosthetics often have inaccurate perceptions of their gait, both initially and with practice.
• The focus tends to be on torso position rather than the prosthetic device itself, likely due to limited feedback.
• Providing feedback on prosthetic device behavior and addressing overconfidence could improve training outcomes.

This research, published in the open access journal PNAS Nexus, was supported by the National Institutes of Health and the National Science Foundation [2]. Further investigation into these perceptual discrepancies promises to enhance the effectiveness of robotic prosthetic training and improve the quality of life for users.