TENS (also known as electrotherapy) is a method for relieving chronic pain through electricity. A TENS machine is connected to a few electrode pads which pass small electrical currents across the skin.
Parts of a TENS Machine
Electrode pads
TENS unit
Batteries
Electrical cords

Pain relief
Electrical currents from a TENS machine stimulate the nerves near the electrode pads to provide short-term pain relief. This occurs due to:
1. Nerves stimulated to release pain-relief hormones
2. Blocking pain nerves
Using a TENS Machine
Before purchasing a TENS machine, consult your physiotherapist or chiropractor and ensure that they show you the correct and safe method to use the machine.

How long can you use a TENS unit at one time?
A TENS machine can be used from 30 minutes to up to 2 hours. However, make sure to consult your physiotherapist or chiropractor before use.
When can a TENS machine be used?
Pregnant women in labour
People with chronic pain such as back pain, cancer or arthritis
When/where NOT to use TENS?
On a wound or irritated skin
Near sensitive areas such as the eyes
In or near water
When driving or using machinery
Pregnant women NOT in labour
People with a pacemaker or cochlear implant