Spinal muscular atrophy (SMA) is a rare neuromuscular condition to which all mentioned above issues are completely applicable. Direct current stimulation (DCS) of neural structures is well studied and safe intervention, however, its effects on SMA patients' strength and durability has not been reported for today. The investigators suppose that investigation of DCS action in SMA patient population is an adequate model for visit-free design feasibility, reliability and sensitivity evaluation.