Fig. 2

Effect of the supplier recommended and optimized AFO stiffness on walking energy cost. In the left panel, the average value for walking without AFO, with the supplier recommended AFO stiffness and experimental optimized AFO stiffness are presented. In the right panel, the individual differences between the recommended and optimized AFO stiffness are shown. The circles indicate people with bilateral calf muscle weakness, while the triangles indicates people with unilateral calf muscle weakness. The grey solid line represents no difference between the recommended and optimized AFO. The dotted line represents a 9% reduction (smallest detectable difference) with the optimized AFO stiffness compared to the recommended AFO stiffness. AFO  ankle–foot orthosis. * Dnotes a significant difference, p < 0.001