Electrical stimulation to optimize health has been used, studied and modified since the creation of electricity in the 1790’s. It now comes in small portable devices and has a variety different uses.

There are two common types of electrotherapy machines for public use: the Transcutaneous Electrical Nerve Stimulator (TENS) and the Electrical Muscle Stimulator (EMS).TENS2

The benefits of electrical stimulation include pain relief, muscle activation and acupuncture point stimulation. TENS for pain relief can be used in chronic and acute injuries, nerve pain, and labour pain. EMS is effective in altering the muscle tone, activation and awareness and relieving trigger points in all superficial muscles. It can also increase blood flow to the area to help with healing.

The TENS has a selection of frequency, pulse width and intensity. TENS is ideally suited for pain relief.

The EMS is a style of TENS machine that can be modified in the on/off cycle, frequency, intensity and pulse width. It can either be used for pain relief or to stimulate muscle function.

The TENS machine is best used for pain relief and for stimulating acupuncture points. A frequency of 100- 150 Hz has a short term pain relief function. The stimulation of the nerves overrides the pain sensation and allows the brain to sense a pleasant buzzing sensation instead of pain. This format offers a gentler sensation but has a shorter time of pain relief.

The TENS can also be used at a frequency of 2-4 Hz. This stimulates the slower nerve fibers such as temperature and pain. This frequency stimulates endogenous opioid, your body’s natural pain reliever. This style is less pleasant and can be irritating in severely painful cases but in return offers longer lasting pain relief.

Low frequency TENS with small electrodes can be used over acupuncture points to produce effects similar to acupuncture. The point selection is beyond the context of this article and is best chosen specific for the individual and condition. A commonly used pain relief point is Large Intestine 4.

The EMS machine can also modify an on – off cycle. This is the length of time the machine will buzz and stimulate the nerves and then the rest time. For muscle resetting and trigger point deactivation, a common cycle of 20 seconds on and 10 seconds off is used. The intensity should be set at a pleasant level with no muscle twitching. For muscle activation, it is often a 5-10 second on time 10-20 second rest period. The intensity can be set at a level to make the muscle twitch, however, it should not be unpleasant or painful.

The intensity levels control the volume of electrical impulse. Start at zero and slowly increase until you feel a comfortable, yet strong sensation. Turn the volume as high as you want, without discomfort. The machines can create and exacerbate pain if turned too high. It is best kept at tolerable level.

Contraindications, Precautions:

Do not place the electrodes over electrical implants (such as pacemakers) or in conjunction with electrical monitoring devices, front and back over the heart, on mucous membranes or on open wounds. Avoid using electrodes over the pelvis, low back and abdomen in pregnant women.

Use caution over healing tissue, hairy or dry skin and areas of skin with abnormal sensation.


Consult a therapist or doctor if you have undiagnosed symptoms. Seek medical help if the pain is unrelenting for greater than 5 days.

The electrical devices are certified and will not deliver a high enough dose to damage tissue if used correctly. The machines can be turned up enough to create pain and this is not recommended or beneficial.

Electrotherapy is a safe and effective way to activate muscles and create temporary pain relief. It is widely used for many health conditions.

Written by Stan Metcalfe, Physiotherapist