Inverse Optimal Control Based Enhancement of Sprinting Motion Analysis with and without Running-Specific Prostheses

Abstract

Over the past decade, the sprinting performances of athletes with a leg amputation have come significantly closer to those of their non-amputee colleagues. The differences in the underlying whole-body mechanics of amputee and non-amputee sprinting have not yet been fully explored, though. The aim of this study was to investigate optimality principles applied by amputee and non-amputee sprinters by means of inverse optimal control (IOC). We have formulated hypotheses for five potential elementary optimality criteria and identified their respective weights that allow the closest possible matches to reference motions for both cases. We have established rigid multi-body system models of a non-amputee and a unilateral transtibial amputee athlete. Each of them has 13 degrees of freedom in the sagittal plane and is equipped with torque actuators at all internal joints - except for the ankle joint of the passive running-specific prosthesis. The IOC problem is formulated as a bi-Ievel problem that solves an identification problem in the outer loop and a motion synthesis optimal control problem in the inner loop. We found a set of optimal weights for each of the two athletes with which motions are synthesized that come close to motion capture data. We conclude that the IOC approach is promising for the identification of optimization criteria in sprinting with and without prostheses.