It is widely recognized that physical exercise is safe and people with moderate Multiple Sclerosis (MS) are encouraged to train regularly to improve their skills in motor task execution. Several studies demonstrated that these activities represent an effective low-cost therapy which leads to significant and clinically meaningful improvements in gait and balance in people with MS (PwMS) with mild to moderate walking dysfunction, possibly also by promoting brain plasticity.

There is general agreement within the scientific community on the importance of timing intervention also during the early stages of MS to preserve or improve walking and balance abilities and fostering brain functional adaptation, thus slowing down the disease progression. Previous studies highlighted the need to early identify and manage gait disorders using a multimodal approach tailored on individual's need. Moreover, Functional Near-Infrared Spectroscopy (fNIRS) measures blood flow which accompanies neuronal activity and thus, it can provide spatial information about changes in cortical activation patterns due to the possible effects of exercise on cortical plasticity.

To the best of the investigators knowledge, no published studies have assessed the effect of exercise on mobility and brain activity in PwMS with minimal or clinically undetectable disability. This emphasizes the need of trials investigating the effect of walking exercise as preventive strategy on MS clinical worsening.

Inclusion Criteria:

• Age > 17 years
• Stable disease course (without worsening over 1 point at the Expanded Disability Status Scale in the last 3 months)

Exclusion Criteria:

• Major depression
• Mini-Mental State Examination < 27
• Other cardiovascular or orthopedic diseases that interfere with physical exercise
• Progressive course of the disease