Experimental: Low-intensity RAGT at progressively increasing intensity

Participants will receive 3 weekly treatment sessions of 3 hours each, for a period of 4 weeks and a total of 12 sessions. In the first two hours of treatment, an experienced physiotherapist will propose a programme based on stretching exercises, muscle strengthening and educational interventions. During the last hour of treatment, subjects allocated to this group will receive gait rehabilitation on the Lokomat device (Hocoma). The device in use will be set at 60% robotic assistance, 50% of load suspension, and a speed initially set at 1.0 km/h, with progressive increments of 0.1 km/h at each training session. The working time consists of bouts of 3 minutes of work alternated by 1 minute of recovery, to be repeated 8 times.

Active_comparator: Conventional RAGT

Participants will receive 3 weekly treatment sessions of 3 hours each, for a period of 4 weeks and a total of 12 sessions. In the first two hours of treatment, an experienced physiotherapist will propose a programme based on stretching exercises, muscle strengthening and educational interventions. During the last hour of treatment, subjects allocated to this group will receive gait rehabilitation on the Lokomat device (Hocoma). . In this case the parameters for setting the machine will be determined by the physiotherapist in charge for treatment administration in relation to the specific characteristics of the patient.

Active_comparator: Over ground training (OGT)

Participants will receive 3 weekly treatment sessions of 3 hours each, for a period of 4 weeks and a total of 12 sessions. In the first two hours of treatment, an experienced physiotherapist will propose a programme based on stretching exercises, muscle strengthening and educational interventions. During the last hour of treatment, the subject will perform a 40-minute walk on a flat surface, preceded by a warm-up phase and followed by a 10 minute warm-down phase each. Subjects will walk back and forth over a distance of approximately 30 metres using their walking aid.