Aim of this project is to investigate and compare in two groups of selected MS patients, with a marked asymmetry of strength, the effects induced on dynamometric, neurophysiological, functional and clinical outcomes by a CT of the less-impaired leg (CT group) compared to a ST of the more-impaired leg (ST group). In order to make comparisons with a population which is not exposed to the condition MS, a third group composed of healthy subjects will also be included in the study.