Due to the functional impairments caused by a lower limb amputation, it is essential to determine the benefits of rehabilitation strategies such as real-time visual feedback training. Such training could allow Veterans with transtibial amputations (TTAs) to better utilize their prostheses and regain the greatest possible level of function. It is not clear how much the prosthetic device (passive-elastic prosthetic foot versus battery-powered ankle-foot prosthesis) and/or the user's response to the prosthesis contribute to the biomechanical and metabolic effects of using these prostheses during walking. Better use of a prosthesis due to targeted real-time visual feedback training could enhance rehabilitation, improve function and reduce asymmetric biomechanics, which in turn could reduce common comorbidities such as osteoarthritis, leg and back pain, and indirectly, diabetes in Veterans with TTAs. The purpose of the proposed project is to systematically establish the metabolic and biomechanical effects of targeted real-time visual feedback training of peak propulsive ground reaction force (GRF) on the biomechanics, metabolic costs, and muscle activity of Veterans with TTAs using their own passive-elastic prosthetic foot and a battery-powered ankle-foot prosthesis. The results of the investigators' research could enhance the use of prosthetic technology to improve the rehabilitation and function of Veterans with lower limb amputations.

Previous studies suggest that use of passive-elastic and/or powered ankle-foot prostheses may not optimize the function of Veterans with TTAs during walking. Targeted, real-time visual feedback training of peak propulsive ground reaction forces increased propulsion and improved walking function in older (\>65 years) and post-stroke adults, who typically have impaired ankle power. To the investigators' knowledge, no research has addressed how visual feedback of peak propulsive force affects the use of passive-elastic or powered ankle-foot prostheses by people with TTAs. In the proposed research, the investigators will determine the underlying metabolic costs, biomechanics, stability, and muscle activity resulting from targeted real-time visual feedback training of peak propulsive force to identify how Veterans with a TTA benefit from more effective use of a passive-elastic prosthesis and/or a battery-powered ankle-foot prosthesis and to determine if the addition of mechanical power provided by a battery-powered ankle-foot prosthesis can further enhance the function of Veterans with unilateral TTAs during walking. 30 Veterans with unilateral TTAs will use their own passive-elastic prosthesis both with and without visual feedback training during level-ground walking, while the investigators measure their metabolic costs and biomechanics. Then, they will use a powered ankle-foot prosthesis (emPOWER, BiONX, Ottobock) both with and without visual feedback training during level-ground walking, while the investigators measure their metabolic costs and biomechanics. With each prosthesis, subjects will walk at 1.25 m/s on a dual-belt force-measuring treadmill 1) with no visual feedback, and then with real-time visual feedback of: 2) peak propulsive force from the "no feedback" condition, 3) +20% greater peak propulsive force, and 4) +40% greater peak propulsive force. During these visual feedback trials, the investigators will ask subjects to match the peak propulsive force displayed on a computer screen with their affected leg. The investigators will also ask subjects to: 5) match symmetric visual feedback of the peak propulsive force from both legs. The investigators will determine if Veterans with TTAs utilizing real-time visual feedback training of peak propulsive force can improve metabolic costs, biomechanical symmetry, and dynamic stability/balance, while using their own passive-elastic prosthesis or a powered ankle-foot prosthesis. The investigators will also establish if Veterans with TTAs can retain the metabolic and biomechanical benefits elicited by real-time visual feedback training once that feedback is removed. Results from the proposed project will be used to inform rehabilitation strategies and prosthetic design, which could ultimately improve health, maximize function, and improve quality of life for Veterans with TTAs.