Core Stability, Functional Capacity, Balance, Strength, and Fatigue in Pediatric Demyelinating Diseases

Core stability (endurance and strength) will be evaluated using standardized trunk endurance tests. The Trunk Flexor Endurance Test measures the duration participants can maintain a 60° trunk flexion position. The Biering-Sørensen Test evaluates trunk extensor endurance in a prone horizontal position supported at the pelvis and lower limbs, recording the time until loss of horizontal alignment. The Side Bridge Test assesses lateral trunk endurance while maintaining a side plank position. All results will be recorded in seconds.

The Modified Star Excursion Balance Test (mSEBT) will be used to assess dynamic postural control. The test consists of three reach directions: anterior, posteromedial, and posterolateral, with the posterior directions positioned at 90° to each other and each forming a 135° angle with the anterior direction. Participants will stand barefoot on the tested limb at the intersection of the three lines and reach as far as possible along each direction with the contralateral limb while maintaining balance and without transferring body weight onto the reaching limb. Before testing, standardized practice trials will be provided to minimize learning effects. Three recorded trials will be performed in each direction for each limb, and the maximum reach distance will be recorded. Reach distances will be normalized to limb length and expressed as a percentage using the formula: (maximum reach distance / limb length) × 100. A composite reach score will also be calculated by averaging the normalized

Functional capacity will be assessed using the 6-Minute Walk Test (6MWT) following standardized protocols. Participants will walk at their own pace for 6 minutes on a 30-meter indoor walkway marked every 2 meters, with turnaround points marked by cones. The total distance walked in meters will be recorded.

For TUG, the person gets up from the chair, walks 3 m, turns back and sits down again. The test will be conducted using the same chair for every child, and the time will be recorded in seconds.

Lower extremity muscle strength and functional performance will be assessed using the 30-Second Sit-to-Stand Test. Participants will perform repeated sit-to-stand movements from a standardized chair for 30 seconds. The total number of full stands completed within the time period will be recorded.

Fatigue severity will be assessed using the Fatigue Severity Scale (FSS), a 9-item questionnaire rated on a 7-point Likert scale (1 = strongly disagree, 7 = strongly agree). The final score is calculated as the mean of all items, with higher scores indicating greater fatigue severity.

Fatigue intensity will be measured using a 0-10 Numeric Rating Scale, where 0 indicates no fatigue and 10 indicates worst imaginable fatigue. Participants will report fatigue levels during activity, at rest, and over the last 24 hours, as well as perceived fatigue over the past week.