Immediate Effects of Heel Support Stiffness on Gait and Balance in Unilateral Transtibial Amputees Using Composite Carbon Foot: Exploratory Randomized Crossover Trial

Background: Heel support stiffness is routinely adjusted during prosthetic alignment, yet its acute effects on balance and gait in high-functioning individuals with transtibial (TT) amputation using advanced prosthetic systems remain unclear. Objectives: To investigate the immediate effects of different heel support stiffness conditions on static balance, functional performance, spatiotemporal gait parameters, and static load line alignment. Study Design: Exploratory randomized crossover trial. Methods: Fifteen male individuals with unilateral TT amputation using composite carbon feet were assessed under three randomized conditions: black wedge, white wedge, and no wedge. Outcomes included clinical balance and functional performance tests, spatiotemporal gait analysis using an instrumented walkway, and static alignment assessment. Results: Single-leg stance duration was significantly increased in the no-wedge condition compared with both wedge conditions ( P < 0.05). No significant differences were observed among conditions for other functional tests, spatiotemporal gait parameters, static load line alignment, or order effects ( P > 0.05). Conclusion: This exploratory trial suggests that acute changes in heel support stiffness have minimal effects on dynamic gait but may influence static postural control in high-functioning individuals with TT amputation. Balance-focused assessments may therefore enhance prosthetic optimization. Clinical Relevance: This study helps clinicians provide informed alignment decisions by highlighting the sensitivity of static balance to heel stiffness adjustments. ( J Prosthet Orthot . 2026;X:XX–XX)