Transcutaneous Electrical Nerve Stimulation vs Electrical Muscle Stimulation

TENS VS EMS - Physiogramworld

Although TENS and EMS unit deliver low voltage electric impulses (electrotherapy) to treat acute and chronic pain, their methodology differs.

A TENS unit stimulates the nerves, the rationale being that the stimulation keeps pain signal from reaching the brain. It uses micro current which gives a tingling sensation in the relief of chronic and acute pain. Some examples include; arthritis, back pain, carpel tunnel syndrome, foot pain, labor pain, multiple sclerosis, sciatica e.t.c.

TENS administered at a low frequency (sensory level TENS, 2-10 Hz), propagates along small afferent sensory nerve fibers specifically to override pain impulses. It does not activate motor fibers, so, no discernible muscle contraction is produced.

The results of laboratory studies suggest that electrical stimulation delivered by a TENS unit reduces pain through nociceptive inhibition at the presynaptic level in the dorsal horn, thus limiting its central transmission. The electrical stimuli on the skin preferentially activate low-threshold, myelinated nerve fibers. The afferent input from these fibers inhibits propagation of nociception carried in the small, unmyelinated C fibers by blocking transmission along these fibers to the target or T cells located in the substantia gelatinosa (laminae 2 and 3) of the dorsal horn.

EMS uses a cycle of stimulation, contraction and then relaxation, to increase blood flow to the area, which decreases inflammation and promotes healing and muscle growth. It mimics the action potential that comes from central nervous system. By stimulating the muscles at their basic structure, an EMS unit causes muscle contractions similar to those obtained by exercise. The EMS units are specifically used for muscle strengthening, rehabilitation purpose, preventing disuse atrophy, relaxation of muscles, cosmetic muscle toning. In addition, EMS is used for many other applications such as range of motion improvement, increased circulatory action and the prevention of blood clots.

EMS is typically provided at higher frequencies (20-50 Hz) expressly to produce muscle tetany and contraction that can be used for “functional” purposes.

Both types of therapies are convenient, in that they are used at home, and the patient controls the dose, generally by way of either a knob or a switch. The electrodes are user-replaceable, though placement instructions are given and monitored by a physical therapist.

A Yale University study entitled Neuromuscular Electrical Stimulation for Skeletal Muscle Function discussing electrical stimulation (ES), neuromuscular electrical stimulation (NMES), transcutaneous electrical nerve stimulation (TENS), and functional electrical stimulation (FES) states that the potential that electrical stimulation holds for rehabilitation recovery is immeasurable. It is used to improve muscle strength, increase range of motion, reduce edema, decrease atrophy, heal tissue, and decrease pain.

REFERENCES

Wikipedia (2016) Electrical muscle stimulation. [Online] Available from: https://en.wikipedia.org/wiki/Electrical_muscle_stimulation

Yu, F. C. (2015) Introduction to Transcutaneous Electrical Nerve Stimulation (TENS). http://exploreim.ucla.edu/news/introduction-to-transcutaneous-electrical-nerve-stimulation/ 

Melzack R, Wall PD. Pain mechanisms: a new theory. Science. 1965 Nov 19. 150(699):971-9.

Taylor, D. C. (2015) Transcutaneous Electrical Nerve Stimulation (TENS) for Pain Management. http://www.medicinenet.com/transcutaneous_electrical_nerve_stimulation/article.htm

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