title: Prosthetic ankle push-off work reduces metabolic rate but not collision work in non-amputee walking.
abstract: Individuals with unilateral below-knee amputation expend more energy than non-amputees during walking and exhibit reduced push-off work and increased hip work in the affected limb. Simple dynamic models of walking suggest a possible solution, predicting that increasing prosthetic ankle push-off should decrease leading limb collision, thereby reducing overall energy requirements. We conducted a rigorous experimental test of this idea wherein ankle-foot prosthesis push-off work was incrementally varied in isolation from one-half to two-times normal levels while subjects with simulated amputation walked on a treadmill at 1.25 m · s(-1). Increased prosthesis push-off significantly reduced metabolic energy expenditure, with a 14% reduction at maximum prosthesis work. In contrast to model predictions, however, collision losses were unchanged, while hip work during swing initiation was decreased. This suggests that powered ankle push-off reduces walking effort primarily through other mechanisms, such as assisting leg swing, which would be better understood using more complete neuromuscular models.
authors.affiliation: Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Caputo
authors.affiliation: Department of Mechanical Engineering and Robotics Institute, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
authors.forename: Steven H
authors.initials: SH
authors.lastname: Collins
mesh_terms: D000328:Adult; D000674:Amputees; D000842:Ankle / Q000502:physiology*; D000843:Ankle Joint / Q000502:physiology*; D001186:Artificial Limbs; D004734:Energy Metabolism / Q000502:physiology; D005684:Gait / Q000502:physiology; D006801:Humans; D008297:Male; D019736:Prostheses and Implants; D019415:Torque; D016138:Walking / Q000502:physiology*