Differences between TENS and EMS for FES?

Hi everyone!

I have some doubts about Functional electrical stimulation (FES). FES can elicit muscle contractions to persons with neuromuscular disorders (such dorsiflexion/plantarflexion in stroke subjects). What I wanted to know is can this "production" of movement be achieved with a Transcutaneous Electrical Nerve Stimulation (TENS) signal or an Electrical Muscle Stimulation (EMS) signal? Could both do it?
Is the difference between EMS and TENS simply where you put the electrodes (ie the area to be stimulated), apart from different electrical signals? So if I put an electrode (-) over a nerve and the other (+) in the motor point of the muscle I have TENS? and if I place both electrodes over the muscle directly (in the muscle's origin and insertion for e.g.) I will have EMS?

Thank you for your replies.

Hi pmelopt

I am not an expert on Electrotherapy and so I may not have all my facts straight. However my understanding is the EMS is a more general term for and electrotherapy device that stimulates muscle via the motor nerve. FES is a type of EMS. FES units have the advantage in that you can control more parameters of the on/off phasing and as well as packing accessories like foot switches and hand controlled switches so you can better get the muscle contraction when you wante it and how you want it. They also have the advantage in that they are designed to deliver the minimum amount of sensory stimulation feasible so that you can better tolerate the current.

You can use TENS units to deliver a stimulation to the motor nerve. You just have to select the right frequency to optimise muscle stimulation (sorry can't remember off the top of my head what that is but an electro therapy text will tell you). some of the cheaper models may not offer the optimal frequency needed. Remember TENS units have been designed to optimally stimulate the sensory fibres so have designated range of frequencies accordingly. However TENS units don't have the convenience of application that an FES unit has for muscle stimulation.

FES is way more efficient and comfortable for the patient than the older EMS devices.

If you are not having success with FES then either there is something wrong with the machine, you aren't applying it correctly or you may be expecting too much from the unit. Personally I would stick to an FES device because of that added applicability - even if the unit costs a bit more than a TENS unit.

TENS cannot be used for FES/EMS. The waveform is different and the TENS only penetrates superficially to the sensory receptors. Some FES/EMS units do have the ability to perform TENS and Interferrential. However the main anser here is that there is NO comparison in what you need to stimulate muscle contraction. You require an FES/EMS unit. A TENS unit will not suffice.