Combination units allow you to use two or more modalities, expanding your treatment options.
TENS units use either low frequencies (2-4 Hz) or high frequencies (80-100 Hz) to block pain impulses to the brain. This helps the body produce more natural pain relieving substances and increase blood flow to the area - both help relieve pain. Relief can last for hours.
EMS units (or Electrical Muscle Stimulation) help reduce or prevent muscle atrophy, the weakening and then loss of muscle tone that happens after injuries or surgery. It helps increase blood flow and range of motion and increase muscle strength and endurance. It can also help with pain management by assisting in relieving muscle pains from spastic muscles, tight muscles or sore muscles. EMS signals pentrate deeper than TENS signals and the frequency is usually above 200 Hz.
IFC units (interferential current) is a deeper TENS. It modulates at a high carrier waveform frequency of about 4000 Hz which penetrates deeper and with less user discomfort. In the tissues the waveform is canceled out which produces a TENS like signal deep under your skin. These units are used to reduce swelling and pain, speed healing and restore muscle function. If you have not found relief with a TENS unit, anecdotal evidence suggests an IFC unit may help more effectively.