Transcutaneous electrical nerve stimulation (TENS) is a method of providing pain relief. As the name suggests, it involves the application of a mild electrical current to the affected area. Lead wires connected to sticky pads that attach to your skin called electrodes.
How do TENS work?
TENS relieves pain mainly by stimulating the pain gate mechanism. When the tissue becomes damaged, and the pain nerve fibres in the area become irritated and increasingly sensitive, this leads to a heightened perception of pain in that area. However, in that region, there are a number of mechanoreceptors that respond to touch.
Stimulation of these nerve fibres overrides the pain impulses from that area. This is the pain gate mechanism.
Electrical current from the TENS machine stimulates mechanoreceptors at a specific frequency (usually 90-130 Hz). As a result, it causes a pain-relieving effect.
TENS is an extremely popular method of pain relief, it is relatively cheap and easy to use. Compared to some oral pain killers, the side effects are minimal. TENS may provide pain relief in the region of almost 70% of cases suffering from an acute injury.
Application of TENS (Electrical Nerve Stimulation):
TENS machines can now be purchased quite readily from certain retail specialists and are easy to apply. Patients can suffer allergic reactions from the conductive gel, the electrodes themselves, or the tape used to secure them in place, so care should be taken.
Most newer machines come with self-adhesive electrodes that can be changed after each application to decrease the risk of cross-infection if more than one person is using the machine.
The settings on the TENS machine are adjusted to suit the individual because each patients symptoms are different. We always recommend that you follow the instructions that come with a machine or seek professional advice. TENS machines usually have 3 main variable settings:
Most machines offer a frequency of approximately 2-200 Hz. To stimulate the mechanoreceptors the frequency should usually be in the region of between 90-130Hz.
The intensity of the current is also adjustable and most machines will be able to reach intensities of between 80-100mA.
3. Pulse Width
This setting controls the period of time that electrical current passes through the electrodes. Many professionals place less emphasis on this setting than on the intensity and frequency, while some machines do not even have this particular control.
Do TENS (Electrical Nerve Stimulation) hurt?
TENS machines should not cause discomfort but it will be possible to feel a slight tingling sensation when the machine is on. Again, as each person is different adjusting the above settings is highly important to gain the maximal effect from the machine.
As with the above settings the position of the electrodes may be varied in response to the individual’s symptoms. An electrode is placed on either side of the painful area. Some practitioners focus on targeting a particular peripheral nerve or acupuncture point.
A contraindication is something that indicates TENs therapy may be harmful.
- If the area of the skin has an abnormal sensation.
- If the patient suffers from seizures or epilepsy seek professional advice
- Using TENS machines in children – this is due to the fact that the child’s growth regions may be affected by electrical current
- If the individual is pregnant always seek professional advice prior to using.
Electrical Nerve Stimulation (TENS) should NOT be used if:
- The patient has a pacemaker
- Patients have an allergic reaction to the electrodes, gel, or adhesive strapping
- Any skin conditions such as eczema
- Patients with open wounds in the area
- Patients who have circulatory problems
- Application to the neck and upper trunk region