Interferential current therapy

Interferential current therapy is a form of electrotherapy devised in the early 1950s by Austrian physician Hans Nemec. It began with the problem that applying low-frequency current directly to the skin causes considerable prickling because of skin resistance and makes it difficult to deliver stimulation deep into the tissues. Nemec came up with a way to overlap two medium-frequency currents inside the body, allowing them to pass through the skin relatively comfortably.

It later spread widely throughout Europe, and today it is frequently used as a standard treatment alongside Hot pack and Therapeutic ultrasound in physical therapy rooms in Korea as well. It is commonly called “ICT,” from its English initials.

The key is a phenomenon called “beating.” When two sounds with slightly different pitches are played at the same time, the sound seems to swell and fade in waves. The same phenomenon occurs with electrical currents. For example, when a 4,000Hz current overlaps with a 4,100Hz current, a rhythm of 100Hz—the difference between them—develops where they meet. This rhythm is called an interferential current. In effect, this applies the phenomenon of Interference in motor learning, which occurs when waves overlap, to treatment.

This causes different things to happen at the skin surface and in deeper tissues. Skin resistance is lower for medium-frequency currents of several thousand Hz, so the skin feels less prickling even at the same intensity. Meanwhile, a low-frequency rhythm that nerves and muscles respond to readily is produced deep within the tissues where the two currents cross.

The treatment device adjusts the character of the stimulation by changing this difference frequency. Higher frequencies around 100Hz feel like gentle, rapid vibrations, while lower frequencies of 10Hz or less feel more like tapping or muscle twitching. There is also a “sweep” setting that varies the frequency up and down within a set range to help keep the body from quickly becoming accustomed to the same stimulation.

Treatment is usually given while the area is being warmed with a Hot pack, or after it has been warmed. The standard method is to place four electrodes in a crisscross X pattern around the treatment area. They are positioned so that the two currents cross right in the center. Cup-shaped suction electrodes are commonly used in physical therapy rooms in Korea, so you feel the skin being gently drawn into the cups to hold them in place, along with the electrical stimulation. There is also a method that uses only two electrodes; in this case, the device sends a current that has already been mixed internally.

The therapist slowly increases the intensity until it feels “tingly but comfortable.” They do not push it high enough to cause pain or strong muscle jerking. You receive treatment lying down or sitting for about 10–20 minutes per session.

During treatment, you may feel a humming vibration, a ticklish tingling sensation, or tapping. After a few minutes, your body may adapt and the stimulation may seem weaker. If that happens, tell the therapist so they can readjust the intensity appropriately.

• People with persistent aching, stiffness, or tightness in the lower back, neck, or shoulders
• People with aching knees due to Knee osteoarthritis
• People who want to ease muscle tension before or after exercise or Manual therapy
• People who find firm pressure applied by hand uncomfortable

Research on interferential current therapy for knee arthritis pain has continued over time. In clinical practice, it is often combined with other care, such as exercise or manual therapy, rather than used on its own.

• Let the therapist know beforehand if you have an electrical device in your body or are pregnant. Electrotherapy is not given to people with pacemakers, and electrodes are not placed on the abdomen or lower back during pregnancy.
• Tell the therapist about your skin condition. Electrodes are not placed over wounds, eczema, or areas with reduced sensation. Reduced sensation makes it difficult to judge the intensity.
• Speak up immediately if you feel stinging or burning. If an electrode lifts away from the skin, the current can concentrate at one point and cause stinging.
• Removing metal accessories can make treatment more comfortable. It is a good idea to remove watches or necklaces near the treatment area beforehand.
• Suction electrodes may leave round red marks, but these usually fade quickly.

Transcutaneous electrical nerve stimulation (TENS) delivers low-frequency current directly through electrodes on the skin. The devices are small, so they are also commonly used at home. Interferential current therapy differs in that it crosses two medium-frequency currents with the aim of stimulating a wider, deeper area with less prickling. Its purpose also differs from that of Neuromuscular electrical stimulation, which contracts muscles to build strength. Most Home TENS and EMS devices for the neck and shoulders use low-frequency currents.