The aim of the study (OVERACT\_V1) is to verify if the isometric contraction of ankle plantarflexor and Hamstring muscles, induces a significant reduction of overactive bladder symptoms in patients with Multiple sclerosis. It's known that the electric stimulation of the Posterior Tibial nerve induces an improvement of overactive bladder symptoms through a modulation of spinal circuitry, which occurs with unknown mechanisms. The investigators' hypothesis is that the voluntary muscular activation may induce a modulation of the sacral root as long as the electric stimulation. 30 patients will be recruited within 2 years, since October 2017 through October 2019. This is a monocentric, randomized controlled , in single blind, not pharmacological study.
