Transcutaneous electrical nerve stimulation (TENS) is a method of providing pain relief. As the name suggests, it involves the application of electrical current to the affected area. This is achieved via a number of electrodes that can be fixed to the skin.
How does TENS work?
TENS relieves pain mainly by stimulating the pain gate mechanism. When tissue becomes damaged, the pain nerve fibres in the area become irritated and increasingly sensitive which leads to a heightened perception of pain in that area. However, in that region, there are also a number of mechanoreceptors which respond to touch. Stimulation of these nerve fibres can override the pain impulses from that area- this is known as the pain gate mechanism. These mechanoreceptors can stimulated by an electrical current at a certain frequency (usually 90-130 Hz) as provided by the TENS machine which in turn causes a pain-relieving effect.
The use of TENS is an extremely popular method of pain relief. It is relatively cheap, easy to use and the side effects are minimal when compared to some oral pain killers. It is thought that TENS can provide pain relief in the region of almost 70% of cases suffering from an acute injury.
Application of TENS:
TENS machines can now be purchased quite readily from certain retail specialists and are easy to apply. However a certain amount of care should be taken as a small proportion of patients suffer from an allergic reaction to the conductive gel, the electrodes themselves or the tape used to secure them in place. 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.
As each patient’s symptoms are different the settings on the TENS machine need to be adjusted to suit the individual. 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 the intensity and frequency while some machines do not even have this particular control.
Does TENS 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. Usually, an electrode is placed either side of the painful area however any number of variations may be possible. 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 skin has 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.
TENS should NOT be used if:
- The patient has a pacemaker
- Patients have an allergic reaction to the electrodes, gel or adhesive strapping
- The patient has 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.