Ordinary TENS devices, very popular in pain management today, send a blast of milli-Amperage electricity directly into the tissue in order to temporarily block pain signals from reaching the brain.  TENS modalities are basically used like an analgesic pain-suppressing medication.  However, the “Pain Gate” effect activated by strong current has been proven to inhibit mitochondrial production of ATP, the “fuel” required by every cell for cellular metabolism.  Common TENS does not contribute to tissue repair or to resolving the underlying cause of painful neuromuscular problems.  Read more in Microcurrent Research.
EMS devices similarly deliver intense, strong milliAmperage currents that can increase blood flow temporarily; however, the effect is designed to tetanize (contract/twitch) muscle and with prolonged use will eventually lead to muscle fatigue, cell exhaustion, and impaired blood circulation.