Neuromuscular electrical stimulation (NMES):

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When you get injured one of the major issues is muscle wasting. This is obviously caused by lack of exercise and also from pain inhibition. The evidence shows pain has an inhibitory effect on muscle activity. Particularly around the knee the activity of the Vastus Medialis Oblique (VMO) is inhibited severely.

So how much of a problem is muscle wasting?



Muscle strength is found to decrease by between 2% to 6% in the first 8 days of immobilisation (Muller,1970). After 2 weeks of not training significant reductions in fitness can be measured & improvements can be lost in months (Kisner & Colby 1996).

Muscle is inhibited when pain is around; this is due to the nerve not firing correctly. This is very significant as to why NMES is effective. In NMES the impulse is sent directly to the muscle making it contract therefore bypassing this issue.

So what exactly is NMES?

Neuromuscular electrical stimulation (NMES) is basically an electrotherapy modality that is used to affect and influence muscle activity. It was originally used in elite sport to improve performance and more recently NMES has moved into physiotherapy practice to help patients.

How does it work then?

It’s as it sounds, you are sending electrical signals directly into the muscle to produce a contraction. You are able to target for endurance or strengthening effects amongst other things. The way it works is down to the different muscle fibre types the body has. The different fibre types fire at different frequencies, which means the NMES can relatively target them.

Here are the different muscle fibre types:


Slow Oxidative: Smallest and least powerful. Lots of mitochondria and blood vessels. This means they use oxygen well and therefore are highly resistant to fatigue. Posture muscles are full of these type and endurance athletes usually have a high distribution of these.

Fast Oxidative-Glycolytic: medium sized and moderately powerful.  So are somewhere between Slow Oxidative and Fast Glycolyyic, so athletes that need to have a combination of speed and endurance will have more of this type.

Fast Glycolytic: Largest and most powerful. Few blood vessels, contain lots of glycogen. They are anaerobic mostly and are designed for short bursts of power but fatigue very quickly. Sprinter and power lifter will have lots of these.

Neuromuscular electrical stimulation changes oxidative enzyme activity, skeletal muscle fibre type & fibre size when used on the correct settings to target the fibre types (Sillen et al 2013).


What does it actually do to the muscles?



The force of muscle contraction achieved is increased as the intensity of the machine is increased (Ferguson et al 1989, Underwood et al 1990).

NMES optimally works alongside exercise for example, lifting a weight with the NMES on. That being said NMES will still  improve muscle strength on its own, which is useful when your injury doesn't allow you to move much or load you injury sufficiently to improve muscle function.

If you want to target endurance then you need to target the slow oxidative muscle fibres. The NMES unit can be set to just contract these fibres, which is good for endurance athletes and as these fibres atrophy the most it is important to be able to target them.
If you want to target the Fast twitch fibres then you can’t purely isolate them but you can get them contracting alongside the slow ones and in doing this you can improve strength.

Overall NMES helps the following:


Prevention of disuse atrophy
Muscle re-education
Relaxation of muscle spasm
Maintaining or increasing range of motion
Prevention of venous thrombosis in selective muscles immediately post-surgery
Increasing local blood circulation
Strengthening weak or injured muscles

So how do I use it?


Electrodes placement:

There are sticky electrodes that you basically stick onto your skin. These work best if both electrodes are placed on the belly of the muscle that you are trying to stimulate. You will need the positive electrode on the motor point of the muscle to get the best contraction with the lowest discomfort.

Larger electrodes are better as there is less current density, therefore less discomfort (Brooks et al 1990).

Settings for Muscle Strengthening:

30 - 35Hz @ 400 µs
4 sec ON / 4 sec OFF (minimum) but usually 10 sec ON / OFF
At least 15 mins alternate days, but usually 30 min / day
Need strong contraction (not just mild twitch) + voluntary as well.

Settings for Muscle Endurance:

20Hz @ 400µs
2 sec ON / 2 sec OFF (minimum)
At least 1 hr day
Minimal contractions needed.

Settings for Very Weak Muscles / Marked Atrophy

10Hz @ 400 µs
2 sec ON / 2 sec OFF (minimum)
minimum 1 hr day
Minimal contraction needed.

What reasons mean that you can’t have NMES?

It is contraindicated in pregnancy however, there appears to be no evidence for this except over the abdomen and lumbar spine of course.

Don’t use on patients with implanted electronic devices such as pacemakers.

Don’t place electrodes around the front of the neck.

Don’t use over the Thorax in cardiac arrhythmias.

Don’t use in patients with peripheral vascular disease or have a suspected DVT.

NMES can be used safely and effectively in patients with cancer, chronic obstructive pulmonary disease, and heart disease. Recent research has actually shed more light on the use of electrical stimulation in these situations.

So what does the evidence say about the effectiveness of NMES?


Integrating NMES in the treatment of patients reduces the total rehabilitation time (Gersh, 1992).

Below are some research examples for what NMES works for:

Knee:

Neuromuscular electrical stimulation & unsupervised home range of motion exercises are cost effective after knee surgery (Levine et al 2013).

Electrical stimulation of vastus medialis muscle with physio improves functional recovery post total knee replacement (Avramidis et al 2011).

Electrical stimulation of the quads supports the regeneration process & results in a provable stronger reduction of the atrophy (Mucha 2004).

Hand:

Electrical Stimulation: Beneficial effect on grip strength & fatigue for RA patients with muscle atrophy of the hand (Pelland et al 2002).

Chronic disease:

NMES improves muscle weakness in adults with progressive diseases such as COPD, chronic heart failure & cancer (Maddocks et al 2013).

Recovery rate:

Evidence is not convincing to support Neuromuscular Electrical Stimulation (NMES) for enhancing recovery from exercise (Malone et al 2014).


So as you can see it can be effective. I have seen reduction in muscle wasting and faster strength and endurance returns in using NMES. So if you have an injury then get booked in to help you to minimise the wasting and get you back to full function faster.

If you need any further information or would like to book an appointment then call Hawkes Physiotherapy on 01782 771861 or 07866195914




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