The rehabilitation engineering community is working towards the development of robotic devices that can assist during gait training of patients suffering from neurologic injuries such as stroke and spinal cord injuries (SCI). The field of robot assisted treadmill training has rapidly evolved during the last decade. The robotic devices can provide repetitive, systematic and prolonged gait training sessions. This paper presents a review of the treadmill based robotic gait training devices. An overview of design configurations and actuation methods used for these devices is provided. Training strategies designed to actively involve the patient in robot assisted treadmill training are studied. These training strategies assist the patient according to the level of disability and type of neurologic injury. Although the efficacy of these training strategies is not clinically proven, adaptive strategies may result in substantial improvements. We end our review with a discussion covering major advancements made at device design and training strategies level and potential challenges to the field.