Elderly people are at risk of falling because of their low toe clearance. Gait training to improve toe clearance could be instrumental in avoiding tripping. We propose using a gait-training robot that applies torque during the pre-swing phase to achieve this goal. It is still possible to revert to their original trajectory after the training, however, depending on the magnitude of the applied torque. We investigated the relation between the magnitude of the applied torque and the change in toe clearance before and after application of torque. We developed a robot and carried out an experiment in which a motor pulls a string embedded on the robotic frame worn by the participants, thereby applying torque during the pre-swing phase. The experimental task included walking on a treadmill for 50 s. We applied torque to the knee during the pre-swing phase for 20 s. The phases before and after applying torque were 15-s normal walking phases with no interference from the robot. We compared toe clearance during the phases before and after applying torque. We found that the toe clearance increased after applying a torque of 8 Nm. We were thus able to verify the influence of torque on toe clearance.