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Electrode size- does it matter?

Would be grateful for thoughts on the relevance of electrode size when using TENS, muscle stimulation or interferential and any potential effects of size I am a veterinary physiotherapist and particularly wonder about any potential impact of using small electrodes on large animals such as horses- does it alter effectiveness? I have seen a large variety in electrode size used by different therapists, from the small self adhesive electrodes (5cmx5cm) to the larger round 75mm or 50x50mm or 90x50mm. When using electrotherapy on horses the distance between electrodes can be much bigger than on humans and you are also trying to treat a larger area. Does using the small 5cmx5cm electrodes concentrate the current on too small an area? Is it possible to have a greater effect by using bigger electrodes in such big animals? What is the best way to choose electrode size?

Emma Sayers

4 years ago

Back to General Electrotherapy

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Dinesh Verma
Dinesh Verma

Dear Prof Tim - Quiet agree with you. Emma - My view is Electrode size would have to depend to TARGET Muscles... If one is doing specific muscle training - then Focus Electrodes OR small size electrodes are perfect - so you recruit targeted muscles and or fibres. but for Group muscle stimulation - Larger muscle may cover greater numbers of muscle fibre recruitment .Remember - small the Electrodes become for GIVEN intensity of current - more will be concentration of current and could result in somewhat discomfort.

Prof Tim Watson
Prof Tim Watson

Generally speaking, the larger the muscle group which is the target of the stimulation, the larger the current that will be needed to achieve the intended result. Similarly, the further apart the electrodes are placed, the greater the required current to achieve outcome. If a 'large' current is put through smaller electrodes, the current density (mA/cm2) will increase and as a general rule of thumb, higher current density results in greater discomfort (and if pushed far enough, can lead to skin irritation and eventually a burn)

You can get a result with smaller electrodes, but patient (whether human or animal) comfort will be improved with larger electrode sizes, and therefore compliance will increase

I am sure that someone, somewhere has a 'formula' but in humans - it is easy to imagine - for stimulation of the quads, it can be achieved with 5 x 5 cm electrodes, but the same result with less discomfort will be achieved with say 10 x 5 electrodes. I might use 5 x 5 on forearm or maybe deltoid or biceps, but personally would not be using 5 x 5 on the quads or hamstrings or even the gastrocs/calf

If in doubt, I would tend to go larger

Would be interested to hear what others think?


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