Multiple sclerosis (MS) is a chronic inflammatory disease characterised by deterioration in the mechanics of the lower extremities and respiratory muscles and a decrease in respiratory function. Fatigue and depression are among the most common symptoms. The aim of this study is to investigate the potential effect of the mechanical properties of the lower extremity and respiratory muscles on respiratory function, fatigue, and anxiety-depression. The sample will consist of 29 MS patients who meet the inclusion and exclusion criteria and volunteer to participate in the study. The sociodemographic data of the individuals will be recorded. Subsequently, the Pulmonary Dysfunction Index (PDI), Modified Medical Research Council Scale (mMRC), Expanded Disability Status Scale (EDSS), Fatigue Severity Scale (FSS), and Hospital Anxiety and Depression Scale (HADS) will be administered to the individuals. The mechanical properties of the accessory respiratory and lower extremity muscles will be recorded using a digital palpation device, and respiratory function and respiratory muscle strength values will be recorded using a portable spirometer. Lower extremity function and strength will be assessed using the 30-second sit-to-stand test. At the end of the study, the level of association between the mechanical properties of the auxiliary respiratory and lower extremity muscles and respiratory function, respiratory muscle strength, fatigue, and depression will be evaluated. The SPSS software package will be used for data analysis. A significance level of p˂0.05 will be accepted. Furthermore, this study will determine the relationship between the mechanical properties of respiratory and lower extremity muscles in MS and provide a different perspective on the clinical management of the disease.