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Prosthetic Model, Not Stiffness or Height, Affects Metabolic Cost of Running

Current stiffness and height recommendations of running-specific prostheses aim to mitigate kinematic asymmetries for athletes with unilateral transtibial amputations. However, a study, published March 30 in the Journal of Applied Physiology, found that prosthetic foot recommendations based on stride kinematics do not necessarily minimize the metabolic cost of running for athletes with unilateral transtibial amputations. Instead, the optimal prosthetic model is one that improves an athlete’s overall biomechanics and thus minimizes the metabolic cost of running.

The researchers investigated how prosthetic model, stiffness, and height affect the biomechanics and metabolic costs of running by measuring ground reaction forces and metabolic rates as ten athletes with unilateral transtibial amputations performed 15 running trials at 2.5m/s or 3m/s. The athletes ran using three different prosthetic models with five different stiffness category and height combinations per model. The Ottobock 1E90 Sprinter foot prosthesis reduced metabolic cost by 4.3 percent and 3.4 percent compared to the Freedom Innovations Catapult and Össur Flex-Run prostheses, respectively. Neither prosthetic stiffness nor height affected the metabolic cost of running. The metabolic cost of running was related to lower peak and stance average vertical ground reaction forces, prolonged ground contact times, and decreased leg stiffness averaged from both legs. Metabolic cost was reduced with more symmetric peak vertical ground reaction forces, but was unrelated to symmetric stride kinematics, according to the study’s authors.

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