Simulating Ideal Assistive Devices to Reduce the Metabolic Cost of Running
(a) The average metabolic power consumed by the three muscles whose energy consumption decreased the most (vasti, iliopsoas, and gluteus maximus) and by the rectus femoris, whose energy consumption decreased marginally. (b) Mean hip adduction (top), hip rotation, hip flexion, and knee extension (bottom) moments are shown for the right leg when unassisted (dashed lines) and when assisted by an ideal hip flexion/extension actuator (solid lines), averaged across 10 subjects; the mean hip actuator torque from Fig 3 is shown for reference (black). The recruitment of the rectus femoris increased to generate more of the necessary knee extension moment during stance, and the superfluous hip flexion moment it generated was neutralized by the ideal actuator. The ideal actuator also provided the hip extension moment originally generated by the gluteus maximus during stance, thereby reducing the co-contraction of the gluteus maximus and gluteus medius in the hip rotation degree of freedom.