Multiple Sclerosis (MS) is an autoimmune disease of the central nervous system and is a chronic and progressive disease characterized by inflammation, demyelination, and axonal degeneration. Due to axonal damage and demyelination, various neurological findings with motor and sensory losses are observed in patients with MS depending on their localization in the central nervous system. These findings vary depending on the location and size of the lesion, frequency, and severity of the disease. It is known that there are 2.8 million people living with MS in the world. Generally, the first symptoms appear between the ages of 20-40, but it is defined as early-onset or pediatric under the age of 18, adult-onset between the ages of 18-49, and late-onset after the age of 50. It is approximately twice as common in women, and is more common between the ages of 20-50, especially in white races. Although four clinical types are defined in MS: relapsing remitting MS, primary progressive MS, secondary progressive MS, relapsing progressive MS, clinically isolated MS has been added to the current classification, and the relapsing progressive MS classification has been abolished and those in this classification have been included in the primary progressive MS class. The relapsing remitting type is the most common, and there are periods of exacerbation (relapse) and remission in this type. Complications that occur during the exacerbation period show full or near-full recovery during the remission period. Various neurological findings such as spasticity, muscle weakness, gait disturbance, cognitive impairment, swallowing problems, bladder-bowel dysfunction can be observed in MS patients, and respiratory complications constitute one of the most common and important causes of death in MS. The risk of death is almost 12 times higher due to respiratory complications, which constitute approximately 47% of the causes of death in MS. Involvement of the pulmonary system, which is usually observed to have deterioration in diffusion capacity, respiratory muscle strength, and ventilation-perfusion ratio, leads to exercise intolerance, hospitalization, and mortality in MS. In MS, the primary factor is the formation of demyelinating plaques in the central nervous system, and the secondary factors include medications used, fatigue due to the disease, increased body temperature, a sedentary lifestyle, and loss of fitness, which all come together to cause pulmonary effects such as respiratory muscle weakness, lung volume deterioration, neurogenic pulmonary edema, sleep-disordered breathing, impaired respiratory control, decreased coughing efficiency, and respiratory failure. When the literature is examined, it seems that there is a need to try new methods in these disease groups to prevent respiratory complications and improve respiration due to pulmonary effects seen in MS. This study aims to investigate the effects of functional inspiratory muscle training, basic inspiratory muscle training, and physical activity applied in addition to respiratory exercises on respiratory muscle strength, respiratory function, cognitive function, walking, balance, functional exercise capacity, physical activity, quality of life, and core muscles in patients with Relapsing Remitting type Multiple Sclerosis.