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The majority of existing passive energy storage and return prostheses for people with below-knee (transtibial) amputation are stiffer than the biological ankle, particularly at slower walking speeds. Additionally, passive devices provide insufficient levels of energy return and push-off power, negatively impacting biomechanics of gait. Here, we present a clinical study evaluating the kinematics and kinetics of walking with a microprocessor-controlled, variable-stiffness ankle-foot prosthesis (945\u00a0g) compared to a standard low-mass passive prosthesis (Ottobock Taleo, 463\u00a0g) with 7 study participants having unilateral transtibial amputation. By modulating prosthesis stiffness under computer control across walking speeds, we demonstrate that there exists a stiffness that increases prosthetic-side energy return, peak power, and center-of-mass push-off work, and decreases contralateral limb peak ground reaction force compared to the standard passive prosthesis across all evaluated walking speeds. We demonstrate a significant increase in center-of-mass push-off work of 26.1%, 26.2%, 29.6% and 29.9% at 0.75\u00a0m\/s, 1.0\u00a0m\/s, 1.25\u00a0m\/s, and 1.5\u00a0m\/s, respectively, and a significant decrease in contralateral limb ground reaction force of 3.1%, 3.9%, and 3.2% at 1.0\u00a0m\/s, 1.25\u00a0m\/s, and 1.5\u00a0m\/s, respectively. This study demonstrates the potential for a quasi-passive microprocessor-controlled variable-stiffness prosthesis to increase push-off power and energy return during gait at a range of walking speeds compared to a passive device of a fixed stiffness.<\/jats:p>","DOI":"10.1038\/s41598-024-67230-3","type":"journal-article","created":{"date-parts":[[2024,7,17]],"date-time":"2024-07-17T07:03:16Z","timestamp":1721199796000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Variable-stiffness prosthesis improves biomechanics of walking across speeds compared to a passive device"],"prefix":"10.1038","volume":"14","author":[{"given":"Emily","family":"Rogers-Bradley","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Seong Ho","family":"Yeon","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Christian","family":"Landis","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Duncan R. 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