Physiotherapy 88(8): 493-9. 44(1), 59-64. Shah, S. and A. Farrow (2012). PRG 3 IFT: Wide Sweep: 1-250 Hz (fixed), 24 sec sweep time (12/12), 4-electrodes, 20 min. Frequency Sweep The basic principle of Interferential Therapy (IFT) is to utilise the significant physiological effects of low frequency (<250pps) electrical stimulation of nerves without the associated painful and somewhat unpleasant side effects sometimes associated with low frequency stimulation. Edema. The preferable clinical option in the light of the available evidence is to use the IFT to bring about local muscle contraction(s) which combined with the local vascular changes that will result (see above) could be effective in encouraging the reabsorption of tissue fluid. At the present time, it is suggested that it is best avoided in these regions), ​Active or suspected malignancy except in hospice/palliative/terminal care, Dermatological conditions e.g. "Interferential therapy machines as possible vehicles for cross infection." Note : Care needs to be taken when setting the sweep on a machine in that with some devices, the user sets the actual base and top frequencies (e.g. Bellew, J. W., Z. Beiswanger, et al. The result of applying a higher frequency is that it will pass more easily through the skin, requiring less electrical energy input to reach the deeper tissues & giving rise to less discomfort. "The effect of three electrotherapeutic modalities upon peripheral nerve conduction and mechanical pain threshold." 1173185, Physiological Effects & Clinical Applications. IFT was conducted with following characteris-tics: isoplanar vector field with 6:6 sweep mode; carrier frequency 4 kHz; beat frequency 100 Hz; and sweep frequency 150 Hz. Sinewave sweep Frequency response 0 f DUT Impulse input 0 t DUT 0 f VNA IFT FT IFT FT Integrate Differentiate Integrate Differentiate Step input 0 f DUT TDR oscilloscope Step response 0 f Impulse response 0 t. 6 The time resolution and time span obtained with the inverse Fourier transform DFR - Dielectric Frequency Response In addition to the 4 key areas identified above, there are several other specialist application for which IFT has been employed. Low frequency nerve stimulation is physiologically effective (as with TENS and NMES) and this is the key to IFT intervention. "A comparison of true and premodulated interferential currents." (2006). PRG 4 IFT: Dual: i) Sweep: 60-160 Hz (fixed), 12 sec sweep time (6/6), 4-electrodes, 20 min. As IFT acts primarily on the excitable (nerve) tissues, the strongest effects are likely to be those which are a direct result of such stimulation (i.e. Phys Ther 90(9): 1219-1238. The most likely mechanism is via muscle stimulation effects (IFT causing muscle contraction which brings about a local metabolic and thus vascular change). "The effect of interferential therapy on swelling following open reduction and internal fixation of ankle fractures." Lambert, I. et al. Using larger electrodes will minimise patient discomfort whilst small, closely spaced electrodes increase the risk of superficial tissue irritation and possible damage / skin burn. Physiotherapy Theory and Practice 19: 99-107. If you make use of the information, please acknowledge its source. Fuentes et al, 2010). (2000). PRG 2 IFT: High Sweep: 100-250 Hz (fixed), 12 sec sweep time (6/6), 4-electrodes, 20 min. 3 insert In other circumstances, it may be necessary to stimulate the tissues for 20-30 minutes. *Frequency Sweep : IFT : Nerves will accommodate to a constant signal & a sweep (or gradually changing frequency) is often used to overcome this problem. PRG 7.1 IFT: Constant Frequency with Vector Sweep (Frequency adjustable 4-160 Hz) PRG 7.2 IFT: 1/1 Shift, Selectable Frequency from 10-160Hz, in step of 10 Hz (frequency reduces by 50% for 1 sec., then increases to 150% for the next 1 sec.) Knowing which was round your machine works is critical to effective treatment. & Interferential Stimulation (frequency of 5000 Hz with three fixed sweep frequencies and one fixed beat frequency.) the interference is generated within the machine unit (Ozcan et al, 2004). "The analgesic effects of interferential therapy on two experimental pain models: cold and mechanically induced pain." "Optimal frequencies for electric stimulation using medium-frequency alternating current." In APS, a negative electrode was placed on the anterior knee joint line and a positive electrode was placed posteriorly on … Treatment times vary widely according to the usual clinical parameters of acute/chronic conditions & the type of physiological effect desired. Variable Frequency (15 Hz to 400 Hz): Moisture and Aging 2. References If desired, the clinicians can select the Combination Stimulation, which combines EMS (for 1 minute and more) and IFT (for 1 minute and more) throughout the treatment session. Physiotherapy Theory and Practice 18: 131-139. sets the base frequency and then how much needs to be added for the sweep (e.g. It has been repeatedly demonstrated that ‘wide’ sweep ranges are ineffective whenever they have been tested or evaluated in the clinical environment. Read more on these physiological effects & clinical applications here ..... Stimulation can be applied using pad electrodes and sponge covers (which when wet provide a reasonable conductive part), though electroconductive get is an effective alternative. Ozcan, J. et al. Despite their size, they are perfectly capable of delivering ‘proper’ interferential therapy, though some have limited functionality and ability for the practitioner to ‘set’ all parameters. There is no evidence that has demonstrated a significant benefit of IFT over active exercise. Physiotherapy 81(2): 82-91. 20 Hz to 20 kHz, you can actually test the acoustic characteristics of an object or a room. A randomised crossover study " Physiotherapy 96(1): 22-29. The skin impedance at 50Hz is approximately 3200 whilst at 4000Hz it is reduced to approximately 40. Gundog, M. et al. Muscle stimulation PRG 1 IFT: Low Shift: 1-20 Hz (fixed), 12 sec shift time (6/6), 4-electrodes, 20 min. These include stimulation as part of the management of incontinence and pelvic floor training (e.g. Using larger electrodes will minimise patient discomfort whilst small, closely spaced electrodes increase the risk of superficial tissue irritation and possible damage / skin burn. (1995). Other Clinical Applications The adjacent diagram illustrates the effect of setting a 90 – 130Hz rectangular sweep. ii) IFT Shift: 1-20 Hz (fixed), 12 sec sweep time (6/6), 4-elect, 20 min. Pulse Duration - 1:1, 1:4, 1:7, 1:9. "Interferential therapy effect on mechanical pain threshold and isometric torque after delayed onset muscle soreness induction in human hamstrings." (2004). So, I was thinking about a small display where the marker (center frequency) can be moved and the -3db points found manually. Burst -2, PWM, Sweep, Combi. "Reviewing approaches to trigger point decompression." Ward, A. R. (2009). IN THE MEANTIME, HEAD FOR THE pdf FILE ON THE DOWNLOAD PAGE. Most multifunction stimulators include all interferential modes, so the practitioner has several machine types to select from (examples below). 10 and 15Hz). FREQUENCY SWEEP Nerves will accommodate to a constant signal & a sweep (or gradually changing frequency) is often used to overcome this problem. Care should be taken with regards maintenance of electrodes, electrode covers and associated infection risks (Lambert et al 2000). Combination therapy Equipments is mainly designed for Home visit purpose having digitally controlled Interferential therapy ,Muscle stimulator TENS with fixed programs used to relieve pain, reduce swelling, repair tissues, promote healing and to restore function.. Combo (IFT MS UST TENS) Unit. (2005). Adedoyin, R. A., et al. Figure 19.11 90–130 Hz rectangular frequency sweep pattern with IFT. *The use of IFT should be considered a part of the whole treatment of the condition. Jorge, S. et al. Physiotherapy 92(2): 95-102. Hurley et al 2004, Johnson and Tabasam 2003, Walker et al 2006, McManus et al 2006, Jorge et al 2006, Gundog et al 2012, Rocha 2012, Atamaz et al 2012) provide substantive evidence for a pain relief effect of IFT. "The effect of combined therapy (ultrasound and interferential current) on pain and sleep in fibromyalgia." The International Society for Electrophysical Agents in Physical Therapy (ISEAPT) is a formal subgroup of the World Congress Physical Therapy (WCPT) and is the leading International organisation concerned primarily with Electro Physical Agents. Physiological Effects & Clinical Applications PRG 1 IFT: Low Shift: 1-20 Hz (fixed), 12 sec shift time (6/6), 4-electrodes, 20 min. The sponges should be thoroughly wet to ensure even current distribution. (2003). able to move the peak of the filter. The principle of using the sweep is that the machine is set to automatically vary the effective stimulation frequency using either pre-set or user set sweep ranges. Queralto, M. et al. When refering to evidence in academic writing, you should always try to reference the primary (original) source. Figure 19.11 90–130 Hz rectangular frequency sweep pattern with IFT. Other patterns of sweep can be produced on many machines, for example a rectangular (or step) sweep. Patients who do not comprehend the physiotherapist’s instructions or are unable to co-operate should not be treated. Recent research evidence supports the benefit of 2 pole application (e.g. It is rather a generic means of stimulation – the machine can be set up to act more like a TENS type device or can be set up to behave more like a muscle stimulator – by adjusting the stimulating (beat) frequency. Yik, Y. I. et al. It is obtained when one carrier frequency remains fixed and the other keeps on changing in frequency at regular interval from lower to higher value and back down. "Does amplitude-modulated frequency have a role in the hypoalgesic response of interferential current on pressure pain sensitivity in healthy subjects? Most machines offer several sweep patterns, though there is very limited ‘evidence’ to justify some of these options. Self adhesive pad electrodes are also available (similar to the newer TENS electrodes) and make the IFT application easier in the view of many practitioners. "Home transcutaneous electrical stimulation to treat children with slow-transit constipation." Arch Phys Med Rehabil 84(9): 1387-94. (2000). Spine 29(20): 2207-16. Ganne, J.-M. (1988). "Modulation of cytokine production by interferential current in differentiated HL-60 cells." The stimulation should be tried in a carefully controlled environment where appropriate equipment is available to correct any pacing problems should they arise. Physical Therapy Reviews 15: 243-252. "Comparison of the efficacy of transcutaneous electrical nerve stimulation, interferential currents, and shortwave diathermy in knee osteoarthritis: a double-blind, randomized, controlled, multicenter study." Modern machines usually offer frequencies of 1-150Hz, though some offer a choice of up to 250Hz or more. Modern machines usually offer frequencies of 1-150Hz, though some offer a choice of up to 250Hz or more. Tabasam, G. and M. I. Johnson (2006). The only sweep pattern for which ‘evidence’ appears to exist is the triangular sweep. The sweep range employed should be appropriate to the desired physiological effects (see below). These can be progressed if the aim has not been achieved and no untoward side effects have been produced. "The transfer of current through skin and muscle during electrical stimulation with sine, square, Russian and interferential waveforms." I WILL UPDATE THE INFORMATION HERE AS SOON AS POSSIBLE. The treatment parameters employed are unlikely to be effective given the information now available. "Comparison of the analgesic efficacy of interferential therapy and transcutaneous electrical nerve stimulation." By careful manipulation of the input currents it is possible to achieve any beat frequency that you might wish to use clinically. and the -3db point is found with the center to edge steps shown. A study by Jarit et al (2003) demonstrated a change in oedema following knee surgery in an IFT group, though the patients did the circumferential knee measures (rather than the therapist) and circumferential knee measurement is not an especially reliable method for identifying oedema as such. In the IFT groups, interferential currents were applied through four suction electrodes positioned to target the quadriceps femoris muscle. Patients who are taking anticoagulation therapy or have a history of pulmonary embolism or deep vein thrombosis should not be treated with the vacuum electrode applications, Similarly, patients whose skin may be easily damaged or bruised, The trunk or pelvis during pregnancy (though this MAY be modified in time in line with the TENS advice. (2003). McManus, F. J. et al. As IFT acts primarily on the excitable (nerve) tissues, the strongest effects are likely to be those which are a direct result of such stimulation (i.e. "An investigation into the analgesic effects of different frequencies of the amplitude-modulated wave of interferential current therapy on cold-induced pain in normal subjects." "The analgesic effect of interferential therapy on clinical and experimentally induced pain." Am J Phys Med Rehabil 91(2): 107-113. The basic principle of Interferential Therapy (IFT) is to utilize the significant physiological effects of low frequency (<250pps) electrical stimulation of nerves without the associated painful and somewhat unpleasant side effects sometimes associated with low frequency stimulation. "Pilot study using transcutaneous electrical stimulation (interferential current) to treat chronic treatment-resistant constipation and soiling in children." All frequencies between the base and top frequencies are delivered in equal proportion. because Nerves will accommodate to a constant signal. There are numerous other variations on this theme, and the ‘trapeziodal’ sweep is effectively a combination of these two. It is difficult to show categorically that this is the case in the tissues but it is reasonable to suggest that the resultant current will be stronger than either of the 2 input currents. The sweep range employed should be One will deliver a full range of stimulation frequencies between the set frequency levels and the other will switch from one frequency to the other. Some IFT devices are capable of generating a ‘surged’ stimulation mode which might be advantageous in that fatigue would be minimised – this surged intervention would be similar, but more comfortable than Faradism. This is due to the impedance of the skin being inversely proportional to the frequency of the stimulation. Most machines offer several sweep patterns, though there is very limited ‘evidence’ to justify some of these options. Arch Phys Med Rehabil 93(5): 748-756. Parkkinen, A., et al. The other effects are more likely to be secondary consequences of these. Bellew et al (2012) evaluated the stimulatory effects of IFT and various Burst Mode currents in terms of their capacity to generate significant quality muscle contraction, the results were supportive of IFT as a treatment option. "The effect of interferential therapy upon cutaneous blood flow in humans." Read more, © Physiopedia 2021 | Physiopedia is a registered charity in the UK, no. Therapy Modes: Burst, Cont. "Interferential therapy: a new treatment for slow transit constipation. Stephenson, R. and E. Walker (2003). You might be wondering what IFT Machine consider as a part of the whole treatment. The choice of treatment parameters will depend on the desired effect. It is designed in such a way that it can be used to provide IFT and USD separately or in a combined manner. "Interferential therapy electrode placement technique in acute low back pain: a preliminary investigation." This produces a very different stimulation pattern in that the base and top frequencies are set, but the machine then ‘switches’ between these two specific frequencies rather than gradually changing from one to the other. (2012). Sreeraj S R WORKING In the interferential therapy method, two medium- frequency alternating currents that interact with each other are used. Interferential Precautions PRG 3 IFT: Wide Sweep: 1-250 Hz (fixed), 24 sec sweep time (12/12), 4-electrodes, 20 min. All frequencies between the base and top frequencies are delivered in equal proportion. (2010). Modern machines usually offer frequencies of 1-150Hz, though some offer a choice of up to 250Hz or more. Photomed Laser Surg 27(3): 467-71. (2001). Pope, G. D. et al. If IFT has a capacity to influence oedema, the current evidence and physiological knowledge would suggest that a combination of pain relief (allowing more movement), muscle stimulation (above) and enhanced local blood flow (above) is the most likely combination to be most effective. Sontag, W. (2000). Clin Physiol 20(1): 2-7. (2006). 10 and 25Hz) and with other machines the user sets the base frequency and then how much needs to be added for the sweep (e.g. The sweep range employed should be appropriate to the desired physiological effects (see below). will accommodate to a constant signal a sweep (or gradually changing frequency) is often used to overcome this problem. Arch Phys Med Rehabil 85(3): 409-15. I give my consent to Physiopedia to be in touch with me via email using the information I have provided in this form for the purpose of news, updates and marketing. 10 and 25Hz) and with other machines the user sets the base frequency and then how much needs to be added for the sweep (e.g. Sinewave sweep Frequency response 0 f DUT Impulse input 0 t DUT 0 f VNA IFT FT IFT FT Integrate Differentiate Integrate Differentiate Step input 0 f DUT TDR oscilloscope Step response 0 f Impulse response 0 t. 6 The time resolution and time span obtained with the inverse Fourier transform Phys Ther 89(2): 181-190. Clinical Physiology 21(6): 704-711. (2002). Additionally, some parts of the range might be counterproductive for the primary aims of the treatment. If for example, one current was at 4000Hz and its companion current at 3900Hz, the resultant beat frequency would be at 100Hz, carried on a medium frequency 3950Hz amplitude modulated current. There is a clear difference between these examples – even though the same ‘numbers’ are set. It has been suggested that IFT works in a ‘special way’ because it is ‘interferential’ as opposed to ‘normal’ stimulation. Clearly, stimulation at low frequency (e.g. It may take 10 seconds to go up and 5 seconds to come down, it is known as Sweep , this sweep … It is often regarded (by patients) to be more acceptable as it generates less discomfort than some other forms of electrical stimulation. The information on these pages is provided in good faith and should be treated as such. "Trends in the availability and usage of electrophysical agents in physiotherapy practices from 1990 to 2010: a review." After each change, the analyzer waits until a stable reading is detected before switching to the next step. Physiotherapy Theory and Practice 6: 3-7. Physiopedia is not a substitute for professional advice or expert medical services from a qualified healthcare provider. The sweep range employed should be appropriate to the desired physiological effects (see below). ~1-100Hz – This frequency sweep will increase the inflammatory rate. Alternatively, stimulation with lower frequencies (2-5Hz) can be used to activate the opioid mechanisms, again providing a degree of relief. The basic principle of Interferential Therapy (IFT) is to utilise the strong physiologicaportable iftl effects of low frequency (<250pps) electrical stimulation of nerves without the associated painful and somewhat unpleasant side effects sometimes associated with low frequency stim. The principle of using the sweep is that the machine is set to automatically vary the effective stimulation frequency using either pre-set or user set sweep ranges. To a greater extent, the therapist does not have to concern themselves with the input frequencies, but simply with the appropriate beat frequency which is selected directly from the machine. TENS). To produce low frequency effects at sufficient intensity and at sufficient depth, patients can experience considerable discomfort in the superficial tissues (i.e. (2013). The effects of tissue stimulation with these 'medium frequency' currents (medium frequency in electromedical terms is usually considered to be 1KHz-100KHz) has yet to be established. frequency of say a filter, If the filter variable, you would like to be. The exact frequency of the resultant beat frequency can be controlled by the input frequencies. Advanced DC Winding Resistance Ripple and Slope 3. (2004). (2012). Colorectal Dis 15(1): e35-39. For patients who can not generate useful voluntary contraction, IFT may be beneficial as it would be for those who, for whatever reason, find active exercise difficult. The basic principle of Interferential Therapy (IFT) is to utilize the significant physiological effects of low frequency (<250pps) electrical stimulation of nerves without the associated painful and somewhat unpleasant side effects sometimes associated with low frequency stimulation. for pain relief through all the outputs. "Stimulation of bone healing with interferential therapy." 45-90Hz: this frequency will reduce the sympathetic nervous system allowing increased activity of the parasympathetic system and blood supply. Walker, U. Interferential Therapy (IFT / IFC) has been widely used in therapy for many years (usage reviewed in Pope et al, 1995 and more recently Shah and Farrow, 2012), Its use is probably disproportionate to both the volume and the quality of the published evidence, though it is strongly supported on an anecdotal evidence level, and several reviews are indicating an overall supportive evidence base, especially for pain based management (e.g. Atamaz, F. C. et al. Physician Assistant 26(12): 37-41. There is limited evidence at present for the ‘strengthening’ effect of IFT (though this evidence exists for some other forms of electrical stimulation), though the paper by Bircan et al (2002) suggests that it might be a possibility. There is no known physiological difference between the effects of IFT produced with 2 or 4 electrode systems. PRG 2 IFT: High Sweep: 100-250 Hz (fixed), 12 sec sweep time (6/6), 4-electrodes, 20 min. Stimulation of the motor nerves can be achieved with a wide range of frequencies. sweep triangle sweep rectangle sweep trapezoidal (A) Triangular sweep pattern. The following parameters were used in all IFT groups: 125 micros pulse duration, 4 kHz carrier frequency and a 6/6 sweep. "Efficacy of two forms of electrical stimulation in increasing quadriceps strength: a randomized controlled trial." Jenson, M. G. (2002). It is suggested that short treatment times are initially adopted especially with the acute case in case of symptom exacerbation. Types of sweep patterns-Triangular sweep patterns; Rectangular sweep pattern; Trapezoidal sweep patterns; 3) 4 pole and 2 pole IFT: It is possible to continue to stimulate the muscle beyond its point of fatigue – the contractions are forced via the motor nerve – and short stimulation periods with adequate rest might be a preferable option. Fuentes, J. P. et al. It is not capable of direct stimulation of nerve in the common context of such stimulation. The are 4 main clinical applications for which IFT appears to be used: In addition, claims are made for its role in stimulating healing and repair. For example to assist the patient to appreciate the muscle work required (similar to surged Faradism used previously – but much less uncomfortable). The possibility that the IFT is acting as an inhibitor or sympathetic activity remains a theoretical possibility rather than an established mechanism. There is no research evidence to support the continuous progression of a treatment dose in order to increase or maintain its effect. It has been repeatedly demonstrated that ‘wide’ sweep ranges are ineffective in the clinical environment, Note : Care needs to be taken when setting the sweep on a machine in that with some devices, the user sets the actual base and top frequencies (e.g. enormously. Using frequency sweep in the audio frequency range, i.e. IFT has been claimed to be effective as a treatment to promote the reabsorption of oedema in the tissues. Interferential therapy (IFT) is a popular electrotherapeutic modality for pain management. (2002). The pattern of the sweep makes a significant difference to the stimulation received by the patient. It is suggested that as a general rule, if the patient has a pacemaker, it is best to avoid all electrical stimulation, but like TENS, if it is a treatment that is needed. Journal of Hospital Infection 44: 59-64. PRG 4 IFT: Dual: i) Sweep: 60-160 Hz (fixed), 12 sec sweep time (6/6), 4-electrodes, 20 min. Self adhesive pad electrodes are also available (similar to the newer TENS electrodes) and make the IFT application easier in the view of many practitioners. 45 – 90Hz – This frequency sweep will make the sympathetic nervous system depress which may so allow the increased activity of the parasympathetic system, and also increase the blood supply in … Ozcan J, Ward AR, Roberson VJ (2004). Increased local blood flow In addition, claims are made for its role in stimulating healing and repair and for various specialised application – e.g. There may indeed be significant effect on tissue other than nerves, but they have not as yet been unequivocally demonstrated. The other effects are more likely to be secondary consequences of these. J Hosp Infect. https://www.physio-pedia.com/index.php?title=Interferential_Therapy_/_Interferential_Current_(IFC)&oldid=218287. "Effects of electric stimulation on C and A delta fiber-mediated thermal perception thresholds." Recently, numerous ‘portable’ interferential devices have become easily available. The principle of using the sweep is that the machine is set to automatically vary the effective stimulation frequency using either pre-set or user set sweep ranges. (2004). *The use of IFT should be considered a part of the whole treatment of the condition. The effects of tissue stimulation with these 'medium frequency' currents (medium frequency in electromedical terms is usually considered to be 1KHz-100KHz) has yet to be established. You move the center freq. Rocha, C. S. et al. Top Contributors - Garima Gedamkar, Rachael Lowe, Chee Wee Tan, Laura Ritchie and Kim Jackson. A good number of recent studies (e.g. If for example, one current was at 4000Hz and its companion current at 3900Hz, the resultant beat frequency would be at 100Hz, carried on a medium frequency 3950Hz amplitude modulated current. Selection of a wide frequency sweeps has been considered less efficient than a smaller selective range in that by treating with a frequency range of say 1-100Hz, the effective treatment frequencies can be covered, but only for a relatively small percentage of the total treatment time. One will deliver a full range of stimulation frequencies between the set frequency levels and the other will switch from one frequency to the other. Educational resources for practitioners, students and educators, Physiological Effects & Clinical Applications. dermatitis, broken skin, Danger of haemorrhage or current tissue bleeding (e.g. "A single-blind investigation into the hypoalgesic effects of different swing patterns of interferential currents on cold-induced pain in healthy volunteers." Low frequency nerve stimulation is physiologically effective (as with TENS and NMES) and this is the key to IFT intervention. In the example illustrated, the machine is set to sweep from 90 to 130Hz (figure A) employing a triangular sweep pattern. Care should be taken with regards maintenance of electrodes, electrode covers and associated infection risks (Lambert et al 2000[1]). (2001). Logically one could use the higher frequencies (90-130Hz) to stimulate the pain gate mechanisms & thereby mask the pain symptoms. TENS). Therapy Mode: 2P, 4P, 4PV. Rheumatol Int: 1-4. In other words, the lower the stimulation frequency, the greater the impedance to the passage of the current & so, more discomfort is experienced as the current is ‘pushed’ into the tissues against this barrier. Another advantage of the sweep method is the practical fact that some of the time so saved will be used to obtain refine- ments which would have been overlooked using the slower single frequency methods. Fuentes, J. P. et al (2010). A. et al. Current books on Electrotherapy with brief descriptions. The exact frequency of the resultant beat frequency can be controlled by the input frequencies. The others are perfectly safe to use, but whether they are clinically effective or not remains to be shown. The are 4 main clinical applications for which IFT appears to be used: Pain relief Interferential therapy utilises two of these medium frequency currents, passed through the tissues simultaneously, where they are set up so that their paths cross & they literally interfere with each other – hence another term that has been used in the past but appears to be out of favour at the moment – Interference Current Therapy. Christie, A. D. and G. L. Willoughby (1990). The key difference is that with a 4 pole application the interference is generated in the tissues and with a 2 pole treatment, the current is ‘pre modulated’ i.e. Petrofsky, J. et al. The basic principle of Interferential Therapy (IFT) is to utilise the significant physiological effects of low frequency (<250pps) electrical stimulation of nerves without the associated painful and somewhat unpleasant side effects sometimes associated with low frequency stimulation. If for example, one current was at 4000Hz and its companion current at 3900Hz, the resultant beat frequency would be at 100Hz, carried on a medium frequency 3950Hz amplitude modulated current.