The Complete Guide to TENS Units

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truMedic TENS Unit Electronic Pulse MassagerIf you’re looking for a non-invasive, drug-free way to treat pain, a TENS unit is a smart choice. A TENS unit is a small, battery-operated machine that transmits electrical pulses to the body.

Electrodes connect the machine to your body through small self-adhesive pads. These small pads allow you to direct the electrical impulses directly to the affected area of the body.

TENS units are typically used to treat pain, including:

  • Back pain
  • Knee pain
  • Neck pain
  • Arthritis

Although less common, these machines may be used to help treat period pain, migraines, sports injuries and early labor pain. TENS machines may be used as a singular form of treatment, or they may be combined with other treatments.

Some people are able to reduce the amount of pain medication they take after using these machines, but these results are not experienced by everyone. Before you reduce or stop taking your pain medication, consult with your doctor for guidance and advice.

While these machines may not work for everyone, most patients reduce or eliminate their pain after using a TENS machine. Many people are able to resume their normal daily activities quicker than they would using conventional forms of pain therapy.

Because these machines are small, lightweight and portable, they can be used at work or on the go. The pads are small and discreet, so they can easily be hidden underneath clothing. The unit itself is small enough to fit in your pocket.

At one time, portable TENS units were only available with a prescription and were very expensive. Today, you can purchase machines over the counter, but some machines are still pricey.

How Does a TENS Unit Work?

Omron electroTHERAPY Pain Relief Device PM3030TENS units are believed to work in two different ways, depending on how high you set the pulse rate.

On the normal setting (90-130 Hz), the electrical impulses generated by the unit are believed to block the pain messages being sent to the brain. This belief is based on the “gate theory.”

The Gate Theory

This theory suggests that the central nervous system has a gate mechanism built into it. When the gate is open, pain signals are able to pass through to the brain and we feel pain as a result. If the gate is closed, the pain messages are effectively blocked and we do not feel any pain.

The impulses from the TENS machine actually stimulate non-pain-carrying nerves, effectively closing the “gate.” These signals move more quickly than the slower pain signals.

The brain becomes preoccupied with the quick impulses transmitted by the TENS machine and pain signals are unable to make their way through. This is why most people experience temporary pain relief when they rub or massage the painful area.

Stimulating Endorphin Production

On a lower setting (2-5 Hz), the pulse stimulates the body just enough to start producing endorphins. Endorphins are like your body’s own natural form of morphine. They block pain signals to provide you with some relief.

While most TENS units are basic in nature, you can also purchase more sophisticated, dual channel units. These emit a biphasic waveform and come with a range of different features that include:

  • Controls that allow you to select different frequencies
  • A timer
  • A convenient mode selector
  • Separate output controls to multiple leads
  • Pulse width adjustments

How to Use a TENS Unit


HealthmateForever Hands Free TensEvery TENS unit will come with its own set of instructions that you need to read and follow carefully. While it is possible to purchase a unit online or over the counter, you should consult with your physician or physiologist before using a TENS machine.

Below is basic guide to using a TENS unit, but we must stress the importance of reading and following your machine’s individual instructions carefully.

  1. Clean the areas of the skin where the electrodes will be placed with rubbing alcohol. Make sure that the skin is dry before using the machine.
  2. Place a thin layer of gel onto the bottom of each electrode pad. This gel will help the signal get to the nerves that are underneath your skin.
  3. Attach the self-adhesive pads to either side of the affected area. The pads should be at least one inch apart. Make sure that the machine is turned off before positioning the adhesive pads.
  4. The machine will have a dial that allows you to control the strength of the electrical pulses. Before turning on the unit, adjust the dial so that the machine is on a low setting.
  5. When you turn the machine on, you may feel a slight tingling sensation. If need be, you can gradually increase the strength of the impulses until you feel a strong but comfortable sensation. Reduce the strength if you feel any discomfort or pain.
  6. Turn the TENS unit off once your session is complete. Remove the adhesive pads.

A typical session lasts 15-20 minutes, and you can use your machine several times per day.

To maximize the benefits of a TENS unit, you need to make sure that you place the electrodes in the right place. Otherwise, the pain may not be lessened, or it may make the pain even worse. If you’re still unsure of where to place the pads, consult with your doctor.

Note: Placing the electrodes on certain areas of the body can be unsafe and potentially dangerous. Please see the Safety Precautions section below for more information.

Possible Side Effects

Most people use TENS machines without experiencing any side effects. The most common side effect is not related to the machine itself, but the self-adhesive pads.

Some users experience skin reactions because of the pads. In most cases, this can be avoided or remedied by ensuring that you do not place the pads in the same exact location with each use.

If the pulse is too high or you use the TENS machine too often, the stimulation can cause pain or muscle twitching.

Aside from these two minor side effects, most users are able to use the unit safely and without any adverse reactions. However, there are certain individuals that should not use a TENS unit (see the section below for details).

Safety Precautions

Although TENS machines are generally safe, there are some individuals who should not use them.

Do Not Use a TENS Machine If:

  • You are pregnant – unless specifically advised by your doctor during labor
  • You have epilepsy
  • You have heart disease
  • You have a pacemaker
  • The cause of your pain is unknown or not diagnosed

Never use a TENS unit while driving or operating heavy machinery. Never use the unit in or near a bathtub or water.

While you can place the electrodes on most areas of the body, there are some areas that are unsafe:

  • The side or the front of your neck
  • Your eyes or your mouth
  • Your heart
  • Your temples
  • Areas of reduced sensation
  • Broken or damaged skin
  • Varicose veins

Some TENS units, particularly those purchased from unreliable sources, may offer pad placement guides that suggest placing the electrodes on your neck or chest area. Never place the electrodes on any of the areas listed above. Consult with your physiologist or physician if you have questions about where to place the electrodes.

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