Difference Between Electrical Muscle Stimulation and TENS

Electrical muscle stimulation or EMS, causes muscle fibers to become 'trained' without having to exercise with weights. It works by delivering electric impulses through electrodes on the skin directly above to the muscles to be stimulated. They then contract as a result. The repetitive contractions at certain frequencies is what trains the muscles.

Muscle simulators come preset with different programs, which cause varied responses from different muscle fiber types. Some programs are designed to improve fatigue resistance and improve endurance, while others will increase strength. Electrical muscle stimulation can be used both as a training and a therapeutic tool.

EMS devices are approved by the FDA in two categories. Over-the counter devices (OTC), and prescription devices. OTC devices are marketable only for muscle toning. They were previously heavily advertised for weight loss, however there was a crack down on this and manufacturers can no longer make these claims.

Prescription EMS devices should be used under supervision of an authorized doctor, rehabilitation specialist and physiotherapists, for relaxation of muscle spasms, increasing local blood circulation, muscle re-education and maintaining or increasing range of motion.

TENS is a similar noninvasive device but is designed to reduce acute and chronic pain. TENS stands for 'Transcutaneous Electrical Neural Stimulation'. It works by stimulating sensory nerves to block pain signals. When the nerves are stimulated by certain frequencies, endorphin compounds are released which bind to opioid receptors in the central nervous system and in turn block the sensation of pain.

For both EMS and TENS devices, there are basic versions available for over the counter sales which can be legally marketed to consumers. They are usually hand held in size, have basic LCD screens and come with a range of preset programs. Professional versions come in suit case type packages and are made of more heavy duty metal with permanent electrodes and accessories. These larger professional rehabilitation and muscle training versions have more complex programs and are only intended for use by healthcare professionals.

This is an example of a combined TENS Unit and Muscle Stimulator System that is OTC.

People who use pacemakers should not use EMS or TENS for obvious reasons. There are also many other warnings specific to various devices so its important to read the manufactures safety information. They generally should not be used on vital parts, such as across the chest, or across the brain, in the mouth or eyes.

Reference to TENS study on pain relief - http://jpet.aspetjournals.org/content/289/2/840.full