Asymmetry index (AI) of the estimated ground reaction force distribution at the heel, metatarsal heads, arches and toes of the foot during linear (LIN) and curved trajectories (Foot-In, Foot-Out). In the ordinate, larger negative values (average ± standard error, SE) of AI represent an increase in vGRF on the lateral part of the relevant foot region. During curved walking, AI of the Foot-Out heel became more negative than that of LIN foot and Foot-In. On the contrary, AI became less negative for Foot-In with respect to LIN foot. At the metatarsal heads, AI showed the opposite behaviour: for Foot-Out, it became slightly less negative with respect to LIN foot. On the contrary, for Foot-In, it became more negative than LIN foot and Foot-Out. *, p < 0.05; **, p < 0.005; ***, p < 0.0005.