The Effects of a 12-week In-phase Bilateral Exercise Programme on the Corticospinal Plasticity in People With Progressive Multiple Sclerosis

Progressive Multiple Sclerosis (MS) is a chronic neurological condition characterized by gradual worsening of neurological function due to damage to the central nervous system. Individuals with progressive forms of MS often experience increasing difficulties with movement, balance, muscle strength, hand function, and cognitive performance. Although disease-modifying medications can reduce inflammatory activity, they have limited effects on the neurodegenerative processes that drive disease progression. For this reason, rehabilitation approaches that promote neuroplasticity-the brain's ability to reorganize and adapt-are considered an important complementary strategy for improving function and quality of life in people with progressive MS. This study investigates whether a structured exercise program based on coordinated bilateral upper-limb movements can enhance corticospinal plasticity and improve clinical outcomes in people with progressive MS. The corticospinal tract is a major neural pathway responsible for voluntary movement, and damage to this pathway contributes significantly to motor impairment in MS. However, some remaining neural connections may still retain the ability to adapt through activity-dependent plasticity. The study examines whether targeted exercise can stimulate these mechanisms. Five participants diagnosed with either primary progressive or secondary progressive MS took part in the study. The research used a single-case experimental design with a concurrent multiple baseline approach, in which each participant served as their own control. During an initial baseline period, repeated measurements were collected without intervention to establish stable reference values. The exercise intervention was then introduced at different time points for each participant. The intervention consisted of a 12-week in-phase bilateral upper-limb exercise program performed three times per week. The training included coordinated movements of both arms performed simultaneously, such as adapted sport-related exercises, functional strengthening activities, and proprioceptive neuromuscular facilitation patterns. Sessions lasted approximately 30-60 minutes and were designed to provide a high number of repetitions while maintaining a safe intensity level. The primary outcome of the study was corticospinal excitability, measured using transcranial magnetic stimulation (TMS). Specifically, the study evaluated the active motor threshold, a neurophysiological measure reflecting the responsiveness of motor pathways in the brain. Secondary outcomes assessed potential functional changes in walking ability, balance, manual dexterity, upper-limb strength, cognitive processing speed, fatigue, and health-related quality of life. By combining neurophysiological measurements with clinical assessments, this study aims to determine whether coordinated bilateral exercise can induce measurable changes in brain excitability and functional performance in individuals with progressive MS. The findings may provide preliminary evidence supporting the use of targeted exercise interventions as part of comprehensive neurorehabilitation strategies for people living with progressive MS.