Muscle weakness is a major disability that is responsible for deeply reducing the overall quality of life (QoL) of patients with Multiple Sclerosis (MS). Research has shown that strength training (ST) has a significant positive effect on the performance of daily living activities in people with MS, resulting in an increased QoL. Several ST methods are currently employed for reducing strength impairment in MS but no one regimen has been portrayed as superior to others. When strength impairment is prominently lateralized to one limb, training is commonly addressed to the weaker side in order to balance the deficit. However, such ST may not always be applicable to a severely weakened limb that is too compromised to sustain it. For these selected patients we hypothesize that training the less affected limb with a Cross Training (CT) approach may overcome the problem, also avoiding patients' frustration and potential withdrawals from rehabilitation programs.