Stimulation will be applied at an intensity of 2 mA for 20 minutes, with an average ramp-up and ramp-down rate of 0.1 mA/s, using circular electrodes of 35 cm² (resulting in a current density of 0.06 mA/cm²) covered with sponges moistened with 0.9% saline solution. A Sooma tDCS™ direct current stimulator (Sooma Oy Ltd, Helsinki, Finland), certified for clinical use, will be used. The anode will be placed over the Cz stimulation site, and the cathode will be placed on the right shoulder. The electrode will be secured to the participant's head using a neoprene cap (Neuroelectrics, Barcelona, Spain) and to the shoulder with a crepe bandage. Gait training will be performed using a treadmill and a body-weight support system consisting of a harness that also serves as a safety mechanism in case of a fall. Each session will last 20 minutes to allow for a sufficient number of gait cycles to promote motor relearning.

The sham tDCS group will use the same device and electrode placement as the active stimulation group. The protocol will consist of a 10-second ramp-up to 1 mA, followed by a 7-second ramp-down to 0.3 mA, which will be maintained for 19 minutes and 40 seconds, and a final 3-second ramp-down to 0 mA. This sham stimulation method is integrated into the Sooma stimulator. Gait training will be performed using a treadmill and a body-weight support system consisting of a harness that also serves as a safety mechanism in case of a fall. Each session will last 20 minutes to allow for a sufficient number of gait cycles to promote motor relearning.

Stimulation will be applied at an intensity of 2 mA for 20 minutes, with an average ramp-up and ramp-down rate of 0.1 mA/s, using rectangular electrodes of 35 cm² (resulting in a current density of 0.06 mA/cm²) covered with sponges moistened with 0.9% saline solution. A Sooma tDCS™ direct current stimulator (Sooma Oy Ltd, Helsinki, Finland), certified for clinical use, will be used. The anode will be placed over the Cz stimulation site, and the cathode will be placed on the right shoulder. The electrode will be secured to the participant's head using a neoprene cap (Neuroelectrics, Barcelona, Spain) and to the shoulder with a crepe bandage.

Timed Up and Go (TUG) Test: Measures the time it takes for the patient to safely stand up from a chair with armrests, walk three meters to a marked line, turn around, return to the chair, and sit down. The patient may use assistive devices if needed.

Timed 25-Foot Walk (T25-FW): Assesses gait speed by measuring the time it takes for a patient to walk a distance of 25 feet.

12-Item Multiple Sclerosis Walking Scale (MSWS-12): A patient-reported outcome measure that assesses self-perceived walking ability by asking about mobility-related aspects over the past 15 days. Values: 12 up to 60. Higher scores mean worse walking ability.

Questionnaire for adverse events

"Modified Borg Scale. It measures the perception of effort and the intensity of physical activity on a scale from 0 (complete rest) to 10 (maximum effort)."