Interferential therapy is a modality that applies currents at around 4000 Hz through the affected area of a patient. Four electrodes are placed in such a way that allows two currents to cross each other and penetrate deep within a joint or body area.
Stimulation of the motor nerves can be achieved with a wide range of frequencies. Clearly, stimulation at low frequency (e.g. 1Hz) will result in a series of twitches, whist stimulation at 50Hz will result in a tetanic contraction.
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.
On the basis of the current evidence, the contraction brought about by IFT is no ‘better’ than would be achieved by active exercise, though there are clinical circumstances where assisted
contraction is beneficial.
For example to assist the patient to appreciate the muscle work required (similar to surged Faradism used previously – but much less uncomfortable).
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.
There is no evidence that has demonstrated a significant benefit of IFT over active exercise. 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
- Pain relief / anaesthetic effect by stimulating the release of endorphins and blocking the transmission of pain impulses (pain gate mechanism).
- Increase in blood flow to promote tissue healing and reduce swelling/ inflammation
- Muscle stimulation to activate weak muscles and overcome muscle inhibition caused by the injury