Amputee perception of prosthetic ankle stiffness during locomotion

Max K. Shepherd*, Alejandro F. Azocar, Matthew J. Major, Elliott J. Rouse

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Background: Prosthetic feet are spring-like, and their stiffness critically affects the wearer's stability, comfort, and energetic cost of walking. Despite the importance of stiffness in ambulation, the prescription process often entails testing a limited number of prostheses, which may result in patients receiving a foot with suboptimal mechanics. To understand the resolution with which prostheses should be individually optimized, we sought to characterize below-knee prosthesis users' psychophysical sensitivity to prosthesis stiffness. Methods: We used a novel variable-stiffness ankle prosthesis to measure the repeatability of user-selected preferred stiffness, and implemented a psychophysical experiment to characterize the just noticeable difference of stiffness during locomotion. Results: All eight subjects with below-knee amputation exhibited high repeatability in selecting their Preferred Stiffness (mean coefficient of variation: 14.2 ± 1.7%) and were able to correctly identify a 7.7 ± 1.3% change in ankle stiffness (with 75% accuracy). Conclusions: This high sensitivity suggests prosthetic foot stiffness should be tuned with a high degree of precision on an individual basis. These results also highlight the need for a pairing of new robotic prescription tools and mechanical characterizations of prosthetic feet.

Original languageEnglish (US)
Article number99
JournalJournal of neuroengineering and rehabilitation
Issue number1
StatePublished - Nov 8 2018


  • Perception
  • Prosthetics
  • Stiffness
  • Variable-stiffness

ASJC Scopus subject areas

  • Rehabilitation
  • Health Informatics


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