Fig. 1

Illustration of the distances between lower limb and obstacle. The solid line represents the leading limb, the dashed line represents the trailing limb, A represents toe-obstacle distance of leading limb, B represents toe-obstacle distance of trailing limb, C represents toe-clearance of leading limb, D represents toe-clearance of trailing limb, E represents obstacle-heel distance of trailing limb, F represents obstacle-heel distance of leading limb, T1 represents the moment of leading limb’s toe is above the obstacle, T2 represents the moment of trailing limb’s toe is above the obstacle