Interferential therapy utilises two medium frequency currents, passed through the tissues simultaneously, where they are set up so that their paths cross & they literally interfere with each other. This interaction gives rise to an interference current which has the characteristics of low frequency stimulation. The exact frequency of the resultant beat frequency can be controlled by the input frequencies. This then allows for physiologically effective and controllable low frequency nerve stimulation. At Active Physiotherapy we use this nerve stimulation, which is also achieved through Transcutaneous Electrical Nerve Stimulation (TENS) or Neuro-muscular Electrical stimulation (NMES), for the following two purposes.
This can be achieved by using higher frequencies to stimulate what is known as the pain gate mechanisms & thereby mask the pain symptoms. Alternatively, stimulation with lower frequencies can be used to activate the opioid mechanisms releasing opiates from higher centres in the brain to have a calming and soothing effect on the painful area.
Stimulation of the motor nerves can be achieved with a wide range of frequencies depending on the type of contraction desired. Your physiotherapist may use this form of treatment in combination with a muscles strengthening program or it may be used to re-educate a muscle or re-stimulate a never that has been damage to help to restore normal function.
The effects of ultrasound can be placed into 2 groups, thermal and non-thermal. Depending on your type of injury and the stage of healing that you are at will determine which of these effects are most desirable at that particular point in time. However it is inevitable that both will occur at the same time but to different degrees.
This relates to the ability of ultrasound to heat the tissues to produce a therapeutic healing effect.
These are the combined effect of what is known as acoustic streaming and cavitation. Acoustic streaming is a small scale circling of fluids around a vibrating structure. This is known to increase the diffusion rates and cell membrane permeability of the vibrating cells. As a result the cells become “excited” and the activity of the whole cell increases. It is this increased cellular activity that is responsible for the effectiveness of the therapy. Cavitation is the formation and growth of gas bubbles by accumulation of dissolved gas in the area which acts to enhance the effect of acoustic streaming.
The application of ultrasound during the different phases of the healing process stimulates and enhances each phase and hence increases the efficiency of the repair process. It helps to speed the whole process up and thus enable the tissue to reach its endpoint faster than would otherwise be the case.