Customers Speak!

  • We received our ultrasound and have been using it nearly every day since. We purchased it to see if we could relieve pains and help us to get moving. We are pleased with the results. When we don't have pain with every step, it is easier to get out and get the exercise that will help with overall health. Thank you! - Gene R.

  • Easy to Order and arrived very quick. - Patricia M.

  • I’ve done business with company twice; first to buy the TENS unit then to buy a replacement cable. The price is great as is the product. It does what they claim and a bit more. I bought it to work my muscles but when my back became injured, I also used it for pain suppression. I was in no hurry to get the product but when it arrived in two days, it was nice. I recommend this company. - Mark H.

  • Seller was great; I will be using them again!!! - Ed H.

  • This is a great product. It helps with the pain. Price was excellent. Did research on it, can’t beat the price. My physical therapist thought it was great and took down the website to be able to recommend to other patients. - Charlotte L.

  • I would definitely use this merchant again. - Melody W.

  • The basic TENS unit I ordered from Medical Products Online is, I think, exactly like the one a physiotherapist used for the back and neck pain I had after a car accident. It really eliminated all the pain! I am now using my own unit for pain in my feet and legs from all the walking I have to do (no transportation options). Within a week of use at less than half the power output, I am glad to say it's working like a magic charm! - Mary L.

  • Medical Products Online is a great website with plenty of options to choose from. Adequate info is provided for all of their medical devices along with reviews from current users. Delivery was efficient. Prices are remarkable. I have already recommended this website to friends and co-workers. - Sharon G.

  • The customer service agents are very helpful, and knowledgeable about the units. I strongly recommend them to all my friends. - Marvelas E.

  • Shipping was fast and I'm also able to contact them about using the ultrasound I purchased. - Gloria B.

  • Total shopping experience great and outstanding customer service. Product delivered as promised. Will be doing future business and recommend them highly for quality products and exceptional customer service. - Raymond S.

  • They are perfect, exactly what I needed. - Lori S.

  • I purchased the MPO 5000 to replace a rental unit from another company. The MPO 5000 was much better quality. It came in a well protected storage case instead of a soft pouch that the overpriced rental unit came it. The rental unit cost was over 4 times more for each month than the MPO 5000 I purchased. I GRADE THIS UNIT EXCELLENT IN EVERY WAY. - K.C.H.

  • Everything is fine in every aspect of the transaction. I needed information about the use of the product and I received it and I received excellent service after sale. - Paul P.

  • Thank you so much for your promptness!! - Tina B.

  • Excellent service. Fast shipment. Product was what I was hunting for at a great price. - Charles M.

  • Excellent price for what turned out to be quality products. The order arrived in 2 days. They exceeded my expectations and I'll order from them again. - Stephen D.

  • Absolutely perfect transaction! I'm amazed at their service and speed of delivery. And best of all, the prices were among the best. A big shout out to Dolores (I hope I got her name right) she really took great care of me. I will be back! P.S. When I read back through this post, I sound like an employee but can assure all that this is an unbiased representation of a very satisfied customer who has shopped with them twice. - Jay P.

  • Easy ordering, fast shipping and delivery. I will order from this merchant again. - Christopher M.

  • I didn't have any surprises. This merchant did exactly what they promised to do and you can't ask for more than that. I will use them again. - Chris B.

  • It came much sooner than I expected!! I'm a happy camper!! Love the unit!! - Donald W.

  • Delivery, customer service, ease of ordering, products and equipment were everything I hoped for and more. Excellent turnaround time, and equipment was perfect. I would highly recommend this company to everyone. - Cathy L.

  • The item which I ordered has worked for me tremendously. It helps with my back pain and I have recommended it to others. - Celestine V.

  • The item which I ordered has worked for me tremendously. It helps with my back pain and I have recommended it to others. - Celestine V.

  • Just what I needed! - Al T.

  • This is a great value for a quality product. I have used this unit daily since I received it and it has performed flawlessly. Ease of set up was apparent and by reading the instructions, this unit can be ready for use in minutes. - Gary C.

  • Fastest shipping I have ever seen! T.E.N.S. unit is Very High Quality. I have paid for many hours at my doctor’s office, now I have many hours pain free. Thanks MPO! - Tammy T.

  • Very pleased with my shopping experience with Medical Products Online. I will recommend this website to all my friends needing this type of product. - John D.

  • I was very satisfied that the stim pads are above the rest that I have used in the past. Talk about being sticky wow they are the best ever! Time for delivery was great and on time as I ordered them for standard shipping. I would order from Medical Products Online again. - Robert C.

  • They use a TENS unit at physical therapy, so the only relief from the pain in my neck, trapezoids was 4 hours a week at PT when they would turn on the TENS!! My Physical therapist told me I could go online and buy one for home use. I immediately got on line and searched TENS units. There were quite a few to choose from. I settled on a unit and before I knew it it was at my door. It did not take me long before I found my favorite setting, when my pain level is a 9 I turn it up a hair, when my TENS unit brings the pain level down to a 4 I can turn it down. I wear it all day, every day! My TENS works better on my pain than any prescription pain killer. I'm wearing it now. One more thing, the company, they are so ready to help. At a point I thought there was something wrong with my TENS, they were ready to send me a new one, immediately, no questions....then I realized I just needed a new battery. I love my TENS and I love the company! - Michelle B.

  • A+ excellent service. - Armando D.

  • Product was exactly as specified, price was good, and shipping and delivery were ahead of schedule. Very good merchant. - Brian L.

  • I bought this product for my wife and it is great. It performs as advertised. It is light weight and produces a wide range of stimulation to the affected area to provide almost instant relief for tense back muscle spasms. I ordered it on a Sunday and as promised, it was delivered two days later and shipping was free. - Robert J.

  • Very fast service and the product is exactly what I ordered. - Rose M.

  • My physical therapist reviewed the specifications for this TENS unit. The transaction was easy and it was delivered quickly after purchase. The TENS unit works as it should. I'm happy with my purchase. - Terry V.
  • I have never purchased online before; my products arrived with excellent quality in a matter of days. Medical products that were always a challenge to find were delivered to my door! - Lynn S.

  • I'm in the medical field and this was money well spent. I had a strained muscle in my left should. After using the unit 2 times a day, I already can feel the difference. I would recommend this product for everyone. - Terry S.

  • I didn't have to use Customer Service but I feel it would have also been excellent. Site is very easy to use and find what you need, couldn't believe how quickly the merchandise arrived and I used the least expensive mode to save money! The prices were very reasonable for the things that I ordered also. I'll definitely shop again in the future. - Joyce C.

Receive emails about special offers, promotions, exclusive product info and news.

Payment Options

Free Shipping Banner Image
  • Home >
  • What Is Interferential Therapy?

What Is Interferential Therapy?

What Is Interferential Therapy?

What Is Interferential Therapy?

Click Here to Purchase our Top Selling Interferential System

Interferential therapy, during the past ten years, has increased in popularity to the point that it is now perhaps the most widely used form of electrotherapy in the United States.

First developed in Europe, where this unique form of stimulation has been utilized for numerous indications, interferential units have been marketed since the early 1950's.

It seems, however, that a great deal of confusion, mystery and perhaps even misinformation still exists concerning this therapy.

The purpose of this article is to shed some light on areas that may be confusing to the clinician, share information on proper treatment protocols and offer a few insights into treating patients with interferential therapy effectively and safely.


The original concept of interferential therapy was developed by Austrian physician, Dr. Hans Nemec, approximately forty years ago. Dr. Nemec proposed that by crossing two slightly different medium frequency alternating currents within the tissue; a third frequency current of greater intensity is created in the deeper tissue.

As an example, a frequency of 4000Hz interfering with another frequency of 4080Hz creates a third current of 80Hz. This is caused by the in phase and out of phase relationship of the two original currents as they alternate from positive to negative polarity.

The third current, referred to as the "beat frequency" becomes the actual therapeutic frequency. One output of the unit is a constant 4000Hz while the second output frequency is adjustable from perhaps 4001Hz to as much as 4250Hz. This form of interferential therapy has become known as "true interferential frequency difference interferential".

A second method of creating the interference effect has been developed in recent years and has become known as "pre-modulated interferential". With this method, both outputs of the unit provide a carrier frequency of 4000Hz, however, each output has the ability to pre-modulate or burst the frequency within the unit. It is important that this unit has the capability of perfectly synchronizing these bursts in the same polarity, at the same time in order to create "pre-modulated interferential" Units capable of pre-modulation are not necessarily pre-modulated interferential and may only provide pre-modulation for the purpose of bi-polar (two electrodes) stimulation.

When considering the relative merits of these two methods, many clinicians have noted that while both create the interference effect, there may be a distinct advantage to the pre-modulated technique. Since the "true interferential" provides an uninterrupted, constant 4000Hz frequency to the tissue, a condition known as Widensky inhibition (depolarization of the nerve fibers) will occur beneath the electrodes.

This will create numbness and what will be perceived by the patient as a reduction in the intensity of current. With pre-modulated interferential, however, since the current is being burst inside the unit itself, Widensky inhibition will not occur and a larger treatment area is established with the actual therapeutic frequency.


Virtually all interferential clinical units are supplied with carbon rubber electrodes. The clinician should be aware that either water soaked sponges or a conducting gel should always be used between the electrode and the tissue. This will insure a uniform contact and provide for even disbursement of the current over the entire surface area of the electrode. If water only is used as a conductive agent, pooling may occur with resulting dry spots under the electrode. The current will then become intensified at the site of best conduction, the water pools, with little or no current flow elsewhere. With "true interferential" units this could result in over stimulation of tissue under the water pools and even possible tissue burns as depolarized tissue will not be able to sense the over stimulation.

While some interferential units still offer the vacuum electrode system, many clinicians have discontinued their use. Extra maintenance, tissue bruising and uneven current flow have been cited as reasons for a reduction in the popularity of vacuum systems.

Self adhesive electrodes are rapidly becoming the favorite of clinicians due to the ease of use, patient acceptance and elimination of possible cross-contamination. Difficult to apply areas such as shoulders, hips and the cervical spine are easily treated with the self-adhesive electrodes. Also, recent improvements in adhesive agents have made longer use possible and prices have been reduced substantially.

If carbon rubber electrodes are used, care should be taken to insure proper current flow. When conductive gels are used, the gel will create a glaze over the surface of the electrodes with long-term use. The glaze may prevent the flow of current over the entire electrode surface. Cleaning the electrode periodically with a mild soap and water and soft brush is recommended. It is not a good practice to use conducting mist sprays in lieu of other conducting agents. This is due to the saline content of the sprays which has been shown to destroy the carbon content of the electrode, thus rendering the electrode useless.

The best selection for this device is re-usable Silver Connector Electrodes.


While frequency ranges vary from manufacturer to manufacturer, basic therapy ranges are fairly consistent. Frequencies which vary from approximately 80Hz to 120Hz are considered most effective for acute pain while lower frequencies of perhaps 3Hz to 5Hz or 2Hz to 10Hz are preferred for the treatment of chronic pain. Some units feature a nerve block setting where both channels produce an output of 4000Hz to create an interferential nerve block to quickly block out acute pain. Most clinicians prefer a setting of 1 Hz to 15Hz for treating acute edema.


When treating acute pain with the 80Hz to 120Hz setting, interferential therapy will provide a release of enkephalin with a treatment time of 10 to 12 minutes. Chronic pain, however, requires 15 to 20 minutes of the 3Hz to 15Hz setting to provide release of beta-endorphins. Nerve block techniques, 4000Hz, normally require 10 minutes or more depending upon the size of the area being treated.


Interferential therapy provides a comfortable, soothing stimulation and should never be strong enough to cause any discomfort to the patient. Higher intensities should not be considered "better" as far as obtaining results. It is important to note that once the patients comfort level is established at the onset of therapy, the intensity should not be increased during the treatment. This could cause over stimulation of the tissue and even minor burns, particularly when treating with a unit that produces "true interferential" due to the Widensky inhibition effect.


This procedure is utilized for muscle strength and rehabilitation and is an added feature of interferential units. Space does not permit adequate explanation of this technique at this time; however, Russian Stimulation may be the topic of a future article


Interferential therapy is considered a very safe modality when used properly for appropriate conditions. Most manufacturers list similar contraindications and precautions, most of which are the same as other electrotherapy devices. It is always recommended that the clinician review each manufacturer’s warnings prior to treatment with any device.

Interferential devices are non-addictive.

Copyright© 2015 - All Right Reserved – Medical Products Online of Connecticut Inc.