Interferential Therapy
Interferential Therapy (IFT): An Overview
Interferential Therapy (IFT) is a type of electrotherapy commonly used to manage pain. It operates by causing two medium-frequency currents with slightly different frequencies to intersect and interfere with each other. For example, if Circuit A carries a current at 4000 Hz and Circuit B at 3980 Hz, their interference produces a beat frequency of 20 Hz, which is effective in pain modulation. This new low-frequency current, generated at the intersection of the two currents within the tissues, is crucial for pain relief.
IFT is primarily used to treat chronic pain, post-traumatic pain, and post-surgical pain. The therapy leverages low frequencies (<250 pps) to achieve therapeutic effects without causing painful or unpleasant side effects. A key advantage of IFT is its ability to target tissues directly, producing desired effects without uncomfortable skin stimulation. This technique is widely employed to induce muscle contractions, promote healing, and reduce edema.
WHAT ARE THE TYPES OF INTERFERENTIAL THERAPIES?
**Vector Effect**: When the interference field is rotated to an angle of 450 in each direction, the field covers a wider area, beneficial for diffuse pathology or when the lesion site can’t be precisely localized.
**Frequency Swings**: Some devices allow speed variation in frequency swings. A rhythmic mode may continuously swing from 0 to 100 Hz in 5-10s and back similarly, or it may hold for 1-6s at one frequency followed by 1-6s at another, with variable transition times.
**Constant Frequency**: Some treatments use a fixed interference frequency. Rhythmic frequency is useful for treating multiple tissue types simultaneously. Varying frequency helps overcome tissue accommodation, where tissue response diminishes over time.
**Frequency Sweep**: This principle involves automatically varying stimulation frequency, using pre-set or user-set sweep ranges. The sweep range should align with the desired physiological effects.
**Sweep Patterns**: The sweep pattern affects patient stimulation. Machines offer several patterns:
– **Triangular Sweep Pattern**: Gradually changes from base to top frequency over 6 seconds, with 1 or 3-second options on some machines. All frequencies between base and top are delivered equally.
– **Rectangular Sweep Pattern**: Switches between the set base and top frequencies rather than gradually changing.
– **Trapezoidal Sweep Pattern**: Combines triangular and rectangular patterns, delivering a full range of frequencies and switching between set levels.
HOW DOES INTERFERENTIAL THERAPY(IFT) WORK?
Interferential current therapy (IFT) works by delivering small electrical stimulations to damaged tissues, enhancing the body’s natural pain response by increasing circulation and promoting hormone release for healing. IFT delivers intermittent pulses to stimulate surface nerves and block pain signals while providing continuous deep stimulation to the affected tissue. IFT relieves pain, increases circulation, reduces edema, and stimulates muscles. A frequency of 100 Hz may stimulate large-diameter A-beta fibers, affecting the pain gate, and inhibit small-diameter nociceptive traffic (C and A-delta fibers), effectively closing the gate to painful impulses. IFT increases blood circulation, reducing swelling by washing away chemicals that stimulate nociceptive nerve endings.
A frequency between 1 and 100 Hz contracts normal innervated muscles. Different frequencies cause different contractions: a low frequency causes a twitch, 5-20 Hz causes partial tetany, and 30-100 Hz causes a tetanic contraction. IFT reduces edema as 100 Hz promotes vasodilation, decreasing swelling. A frequency of 10 Hz activates the musculoskeletal pump, promoting venous and lymphatic return, thus reducing edema. The neurons of the autonomic nervous system, small and poorly myelinated like Aδ and C fibers of the peripheral nervous system, require lower frequencies to increase blood flow and stimulate the autonomic nervous system.