IFT, or interferential therapy, is a type of electrical stimulation used in physical therapy clinics to treat pain, mostly in muscles and joints. It works by sending two medium-frequency electrical currents through the skin via electrode pads. Where those two currents cross inside your body, they combine to produce a lower-frequency current that stimulates tissue at a deeper level than standard electrical stimulation devices can reach.
How IFT Works
The core idea behind interferential therapy is surprisingly simple. A machine delivers two separate electrical currents through two pairs of electrode pads placed on your skin. Each current runs at a medium frequency, typically around 4,000 to 5,000 Hz. The two currents are set at slightly different frequencies, so when they meet inside your tissue, they interfere with each other and produce a new, lower “beat frequency.” If one channel runs at 5,000 Hz and the other at 5,100 Hz, for example, the resulting beat frequency is 100 Hz. That beat frequency is what does the therapeutic work.
The reason for this approach comes down to skin resistance. At low frequencies like 50 Hz, the skin’s electrical resistance is roughly 3,200 ohms, which means a lot of the current gets blocked at the surface and can feel uncomfortable. At 4,000 Hz, skin resistance drops to about 40 ohms. So medium-frequency currents pass through the skin easily and painlessly, then combine deeper in the tissue to create the low-frequency stimulation that therapists actually want to deliver. It’s a workaround: you get the benefits of deep, low-frequency stimulation without the discomfort of pushing low-frequency current through the skin directly.
What a Session Feels Like
During a typical IFT session, a physiotherapist places four electrode pads on your skin around the area being treated. The pads are arranged so that the two currents cross at the target tissue. You’ll feel a tingling or buzzing sensation that most people find tolerable, and the therapist adjusts the intensity based on your comfort. Sessions commonly last 20 to 30 minutes for musculoskeletal pain. For other uses, like treating constipation in children, sessions can last up to 60 minutes with pads placed on the abdomen and lower back.
The therapist can adjust the beat frequency depending on your condition. Lower beat frequencies (around 1 to 10 Hz) are typically used to stimulate muscle contractions, while higher beat frequencies (80 to 100 Hz) target pain relief. The area where the currents intersect forms a clover-leaf shaped zone of stimulation inside the body, positioned at a 45-degree angle between the electrode pairs.
Conditions Treated With IFT
Physiotherapists use IFT for a range of problems, most commonly chronic pain in the back, neck, shoulders, and knees. It’s also used to reduce swelling, improve circulation, and help with muscle rehabilitation after surgery. Some clinics use it for post-surgical recovery after knee procedures like ACL reconstruction or meniscectomy, particularly in older patients. In pediatric settings, IFT has been used to treat chronic constipation by stimulating the muscles of the gut.
Does IFT Actually Work?
This is where things get complicated. IFT is widely used in physical therapy clinics around the world, but the scientific evidence supporting it is mixed, and several major medical organizations have found it lacking.
A randomized controlled trial published in the Journal of the Korean Society of Physical Medicine tested IFT on 40 patients with chronic low back pain. After two weeks of daily 30-minute sessions, the IFT group showed significantly greater improvement in pain during forward bending, disability scores, and balance compared to a placebo group. However, there was no significant difference between the groups for pain at rest.
Larger reviews paint a less optimistic picture. The American College of Physicians concluded in both 2009 and an updated 2017 guideline that there was insufficient evidence to determine whether IFT works for low back pain. The American College of Occupational and Environmental Medicine found the evidence insufficient for shoulder disorders and low back disorders, though it did give a weak recommendation for IFT after certain knee surgeries in elderly patients. The UK’s National Institute for Health and Care Excellence went further in 2016, explicitly recommending against using interferential therapy for low back pain or sciatica. As of 2025, FEP Blue, a major health insurer, classifies interferential current stimulation as “investigational.”
In practice, this means IFT may offer some short-term pain relief for certain people, but it hasn’t been proven effective enough for most medical guidelines to endorse it broadly. Insurance coverage varies, and some plans won’t pay for it. If your physical therapist recommends IFT, it will likely be one part of a larger treatment plan that includes exercise, manual therapy, or other interventions rather than a standalone treatment.
IFT vs. TENS
IFT is often compared to TENS (transcutaneous electrical nerve stimulation), since both use electrical currents for pain relief. The key difference is depth. TENS applies low-frequency current directly to the skin surface, which works well for superficial pain but doesn’t penetrate as deeply. IFT uses its two-channel crossing technique to deliver stimulation to deeper tissues with less skin discomfort. TENS units are small, portable, and widely available for home use, while IFT machines are larger and typically found in clinical settings. Both have similar levels of scientific uncertainty around their long-term effectiveness, though TENS has a larger body of research overall.
Who Should Avoid IFT
IFT is not appropriate for everyone. People with pacemakers or other implanted electronic devices should not use it, since the electrical currents can interfere with those devices. It’s also avoided over areas with active infection, open wounds, or malignant tumors. Pregnant women are generally advised against IFT applied to the abdomen or lower back. If you have a blood clotting disorder or deep vein thrombosis, IFT over the affected area could pose risks. Your therapist should screen for these issues before starting treatment.