ts-DCS will be administered using a direct current stimulator (TCT Research Limited, Hong Kong). 2-mA intensity ts-DCS will be applied to the experimental group, with the active electrode being the cathode electrode. The two electrodes (35-cm2) to be used will be immersed in saline solution (0.9% NaCl). The stimulation electrode (cathodal) will be placed slightly above the spinous process of the T10 vertebral process, while the reference electrode (anodal) will be placed horizontally on the left deltoid.

ts-DCS will be administered using a direct current stimulator (TCT Research Limited, Hong Kong). 2-mA intensity ts-DCS will be applied to the control group, with the active electrode being the cathode electrode. The two electrodes (35-cm2) to be used will be immersed in saline solution (0.9% NaCl). The stimulation electrode (cathodal) will be placed slightly above the spinous process of the T10 vertebral process, while the reference electrode (anodal) will be placed horizontally on the left deltoid. In the application to the control group, the placement of the electrodes will be the same as the active protocol, and unlike the experimental group, the stimulation will be stopped after 30 seconds. This sham procedure has been reported to be a good pseudostimulation method that does not cause significant experimental effects due to the initial itching sensation it provides.

Transcutaneous spinal direct current stimulation (ts-DCS), a neuromodulation technique, is one of the non-invasive brain stimulation techniques. ts-DCS occurs when a continuous and low-intensity electric current passes through electrodes with moist sponges placed on the spinal cord.

Timed 25 Foot Walking Test was used for objective evaluation of walking. In T25-FW, which evaluates lower extremity function, the individual is asked to walk 25 steps as quickly and safely as possible (if he/she uses a walking aid, this is done together). The time spent walking is recorded in seconds.

It is a performance-based test used to evaluate functional mobility and walking speed. The person is asked to get up from the chair he/she is sitting on without support from his/her arms, walk 3 meters at a safe and normal speed, turn around, walk back, sit on the chair again, and the time is recorded in seconds (sec). The test is started with the patient's feet flat on the floor and arms resting on the armrest of the chair. Three repetitions are made and the best result is recorded.

It is a 12-item rating scale used to assess individuals' perspectives on the impact of their disease on their ability to walk. During the test, patients are asked to rate how much MS affects their mobility, such as standing, walking, running, and climbing stairs, on a 5-point Likert Scale (1=almost not at all, 5=extremely). A high score indicates that walking ability is affected or the patient has difficulty walking. The lowest score can be 12 and the highest score can be 60 from the test.

Calculation of walking speed will be done by 2D video analysis method. Kinovea 2D motion analysis software (GPLv2 license, 2019) will be used for analysis. The method has validity and reliability. The videos taken with the cameras placed laterally will be uploaded to the program and the necessary calculations will be made.

The scale, which includes the experience of fatigue, its causes and its effects on daily life, consists of 9 questions and is a Likert-type scale where each question takes a value between 0 and 7. The highest score reached is 63. A score of 36 or above indicates a high perception of fatigue severity.