T.E.N.S., or Transcutaneous Electrical Nerve Stimulation is a unit that stimulates your nerves via an electrical current through your skin. 

The TENS unit is powdered by a  9 volt battery, which produces pain relieving electrical pulses. Either two (single channel) or four (dual channel) self-adhesive electrodes are applied to the skin and attached to the TENS unit with lead wires

Modified electrical pulses are then passed from the TENS unit via the lead wires and electrodes, to the nerves which lie underneath the skin surface. It works on the superficial and spinal nerves traversing to the brain

TENS is a non-invasive tool to assist with pain relief. Regular application of the TENs machine can result in reduced pain for up to 4 hours following use. TENS is considered a pain relief tool and not considered curative. The degree of pain relief declines with prolonged use, however, variation of electrode placement may combat this.

Setting the Mode

Three mode settings: Normal, Burst and Modulation

1. Consistent Stimulation at the frequency and pulse wideth setting: Most commonly used for acute pain relief.

2. Modulation: the freuqncy varies between different settings to help reduce nerve adaptation. This is useful for acute and chornic pain relief

3. Burst Mode: useful in chronic pain relief. The unit will send through a burst of pain reliving power

How Long Should You Use a TENS Machine

The following settings are recommended:

Acute pain: 20-60min up to 4x a day

Chronic pain: 20-30 min up to 5x a day

Learning the Lingo

Pulse Rate

aka Hertz or Frequency or "Pulses Per Second." The Frequency of the TENS unit waveform can range rom approximately 1-250Hx depending upon the model.

80-120Hz - acute pain

35-50Hz - muscle stimulation

2-10Hz - chronic pain

Pulse Width

The pulse width is how wide each pulse is, measured in microseconds. This usually ranges from 1-250uS. 

The HIGHER the pulse width the more AGGRESSIVE the stimulation feels. If the pulse width is too low, the patient may not perceive the stimulation

The following settings are recommended:

175-200uS

Amplitude

aka Intensity or Milliamps (mA). The amplitude is what you feel when you "turn the unit up."

This is what causes the buzzing sensation of the TENS unit to go higher or lower. This ranges from approximately 0-100mA. This is often set to patient comfort levels. 

How do TENS units work?

There are 2 theories behind the TENS unit

1. Gate Theory

attained when "High Frequency"/Pulse Rate is  used (80-10Hz)

This works by clocking the pain signal from the end of the nerves to the brain so when it reaches the brain it is not perceived as pain.

This works very quickly but when the unit is removed from the body, the signals are no longer being blocked

The pain returns quicker, however, this works for a greater percentage of the population (approximately 80% of those who respond positively to TENS units) especially if the patient is taking pain medication

2. Endorphin Theory

attained when "Low Frequency"/ Pulse Rate is used (1-10Hz) or if a Burst Mode is used

Endorphins are the body's natural pain fighting mechanism. When you stub your toe, your immediate reaction is to rub it. This "rubbing" sensation is what triggers localized endorphin release

Endorphins can take up to 45 minutes to reach the area when a TENS unit is applied, but once they are there, the pain relief can last up to 6 hours after the patient takes the TENS unit off. 

This works for about 20% of the population that respond positively to the TENS unit. It takes more patience because it takes longer for the pain relief to begin than with the Gate Theory. 

This does not work well if you are already taking pain medications. 

Please talk to your doctor before beginning use of a TENS unit.