Walking and motor control impairments are among the most common manifestations experienced by people with multiple sclerosis (pwMS) and may already be present in individuals with mild disability. Subtle changes in walking performance can reflect early disease progression, highlighting the need for sensitive clinical outcome measures that capture complex, real-world mobility. Commonly used assessments primarily quantify time or distance and may lack sensitivity to detect early or subtle functional changes in daily-life walking. Successful everyday mobility requires gait adaptability, defined as the ability to continuously adjust walking patterns in response to environmental or task-related challenges, including the processing of external perturbations and internal factors such as fatigue, balance confidence, and fear of falling. Despite its clinical relevance, gait adaptability is not specifically addressed by currently validated clinical tests in pwMS. The Walking Adaptability Ladder Test (WALT), which challenges the interaction between step length, cadence, and walking speed through continuous adjustments, and the Foot Tap Test (FTT), which assesses lower limb motor control and rhythmic coordination, have demonstrated promising measurement properties in other populations but have not yet been evaluated in pwMS. The primary aim of this study is to examine the test-retest reliability and construct validity of the WALT and FTT in pwMS with mild disability. Secondary aims include evaluating the measurement properties of the Balance Recovery Scale and the Gait-Specific Attention Scale in pwMS with mild disability, identifying inertial measurement unit-derived metrics that best discriminate pwMS with low disability from healthy controls, and exploring whether relationships between clinical motor test outcomes and self-reported measures provide complementary insights into subtle gait impairments.

A total of 50 persons with multiple sclerosis (pwMS; EDSS 0-3.5) and 50 healthy controls matched for age (within a 5-year range) and sex will be recruited from the University of León, Ponferrada, and Hospital Universitario de Ponferrada El Bierzo. Test-retest reliability will be assessed exclusively in Spain at these sites, where the specified measurements will be repeated for retest purposes. For validation analyses, single-time-point measurements will be combined with data collected in Italy at the University of Cagliari and Belgium at the University of Hasselt.

The Walking Adaptability Ladder Test (WALT), Foot Tap Test (FTT), Balance Recovery Scale, and Gait-Specific Attention Profile will be assessed twice, with a one-week interval, to evaluate test-retest reliability. The Timed 25-Foot Walk test, 6-Minute Walk Test, 2-Minute Stepping Test, Six-Spot Step Test, Heel Rise Test, Foot Tap Test, and Mini-BESTest will also be performed to assess walking and motor functions. Outcomes will be recorded using time- and observation-based methods, and inertial measurement unit will be used. Cognitive processing speed will be assessed using the Symbol Digit Modalities Test. Patient-reported outcomes will include perceived walking limitations (Multiple Sclerosis Walking Scale), fatigue (Modified Fatigue Impact Scale), balance confidence (Activities-specific Balance Confidence Scale), and fall history and concern about falling (Falls Efficacy Scale-International).

Statistical analyses will be performed to examine test-retest reliability, agreement, and measurement error of the WALT, FTT, Balance Recovery Scale, and Gait-Specific Attention Profile, to assess construct validity through associations with related clinical measures, and to compare performance between pwMS and healthy controls as well as across disability subgroups, using appropriate parametric or non-parametric methods with a predefined significance level (p<0.05)

Inclusion Criteria:

• confirmed diagnosis of definite MS,
• relapse free at least 30 days,
• Expanded Disability Status Scale (EDSS) score between 0 and 3.5

Exclusion Criteria:

• diagnosed with neurological disease other than MS
• cognitive decline that renders the patient incapable of performing tests and questionnaires.
• other neurological, orthopedic, or visual impairments affecting gait

Participants will be recruited from the University of Leon, Ponferrada and Hospital Universitario de Ponferrada El Bierzo. A total of 50 persons with MS will be recruited and divided into two subgroups based on their disability level: EDSS 0-1.5 (n=25), EDSS 2.0-3.5 (n=25). 50 healthy controls, matched for age (considering a 5-year range per subject) and sex, will be recruited for comparison.