Primera TENS/NMES Unit with HAN Waveform allows you to apply TENS and NMES systems to provide a more well-rounded healing process. TENS systems involve non-invasive nerve stimulation through small electrical currents. These currents trigger your body to produce endorphins which help to control your pain. NMES systems are used to reduce muscle spasms, tone weak muscles, and assist in the healing process. They do this through emission of electrical pulses to stimulate repeated muscle contraction.