What Is It?

TENS often refers to the small portable battery operated nerve stimulator. Technically, though TENS refers to all electrical stimulation through the skin (Trans-cutaneous = through skin).

TENS is a relatively safe and non-invasive method of pain relief that is easy to use under guidance of a properly trained health professional. It is important to check with your physiotherapist or doctor before using a TENS.

What Can TENS Be Used For?

TENS has been used extensively to alleviate pain for most parts of the body. It has been shown to be useful for:

• Post-operative pain
• Pain from muscle or ligament sprains
• Various joint and muscle pain including low back pain
• Reflex Sympathetic Dystrophy (also called Complex Regional Pain Syndrome)
• Childbirth
• Pain associated with arthritis.

Its success rate varies depending on the type, severity and cause of the pain.

TENS has been shown to produce short term pain relief. This lasts for a few hours after removal of the stimulation. However its effectiveness for long term pain relief is fairly limited. Nevertheless it may mean that you need less heavy medication.

How Does It Work?

It is unclear exactly how TENS reduces pain, although the proposed "Gate Control Theory" may explain this. As the name suggests, pain seems to be regulated by a "gate" which may be opened (more pain) or closed (less pain).

Nerves of various size and types run from all parts of the body to the spine and up into the brain. The nerves that cause pain are the thin A-delta and C fibres.

Thicker non-painful nerves called A-beta fibres prevent the painful stimulation from reaching the brain by "closing the gate" at the spine. These nerves are stimulated by rubbing the skin or other sensation such as small electric currents. This is why rubbing your hip after you knocked it against the table helps.

The TENS machine generates electrical currents of a particular frequency which selectively stimulate these non-painful Ab nerves. These currents also appear to help release endorphin (naturally occurring morphine-like substances) in the body to further help reduce the pain.

Generally, two types of TENS are used:

1. Hi-TENS (conventional).

This is high frequency low intensity currents useful for more acute pain.

2. Lo-TENS (acupunctural).

This is low frequency high intensity currents used for more chronic or slow pain.

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Application

The TENS unit usually consists of:

The easiest and most common method is to place the electrodes over the painful site. It can then be moved around for best pain relief. The electrodes can be applied across acupunctural / trigger points or along other parts of the nerve. However this is more difficult and your physiotherapist or doctor would be more apted to apply this.

The intensity of the machine is usually adjusted until a prickling or tingling sensation is felt. It should not be painful or cause muscle contractions.

For acute pain, it can be used from 30-60 minutes, once or twice a day to up to 24 hours a day.

For chronic pain, higher intensities may be used. Only 20-30 minutes once a day is required.

Other techniques such as stretches and exercises can be performed while using TENS.

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Precaution

TENS is relatively safe, even for self application. However, there are some precautions to consider:

• Cardiac arrhythmia (if stimulated across heart or front/side of neck)
• Trouble with swallowing and speaking (if stimulated across front of neck)
• Infection (if electrodes are placed on open wounds)

There are few side effects to TENS. The main one is that some people may develop skin irritation from electricity, tape or gel if they are allergic to it.

Generally TENS should be avoided with:

• Open wounds
• Pregnant uterus
• Demand-type pacemakers
• Front and side of neck
• Around eyes
• Areas of skin without sensation
• Other skin problems (eg/ scleroderma, vasculitis)

Remember to check with your physiotherapist or doctor before using a TENS.

They can check whether you can use a TENS, teach you the correct technique, ensure that you are using it safely and answer any questions you may have about it.

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REMEMBER that it is best to see a physiotherapist or doctor before using a TENS unit.