Trunk inclination during linear and curved trajectories and its relation to walking speed. A. Trunk inclination during the linear (LIN) and curved trajectories (counter-clockwise, CCW; clockwise, CW). The curved trajectories present a similar but opposite value. B. Relationship between walking speed normalized to height and trunk inclination across subjects. A linear relationship is present between inclination and speed but only during curved trajectories. *, p < 0.05; **, p < 0.005; ***, p < 0.0005.