EMS glossary

510(k)

The FDA’s premarket notification route for Class II devices. A manufacturer shows its device is substantially equivalent to one already on the market and receives a clearance, which is not the same as an approval.

Biphasic pulse

A pulse with a positive and a negative phase that balance each other, so no net charge builds up in the tissue. The standard waveform in whole-body EMS.

Channel

An independently controlled output of the device. Each channel usually drives a pair of electrodes and can be set to its own intensity.

CK (creatine kinase)

An enzyme released into the blood when muscle fibres are damaged. Very high values after an over-intense first EMS session can indicate rhabdomyolysis.

Contraindication

A condition under which EMS should not be used (absolute) or only after medical clearance (relative).

Duty cycle

The rhythm of stimulation and rest, for example 4 to 6 seconds on and 4 seconds off.

Dry electrode

An electrode that works on bare skin without being moistened, relying on natural skin moisture.

Electrode

The conductive surface that passes current to the skin. Electrode count is not the same as channel count.

EMS

Electrical muscle stimulation: contracting muscles with electrical pulses applied through the skin.

Frequency (Hz)

The number of pulses per second. Most whole-body EMS research uses 85 Hz.

Mid-frequency

Stimulation that uses a carrier frequency in the kilohertz range, modulated at low frequency. Little comparative whole-body research exists.

NiSV

The German ordinance that regulates the commercial use of EMS and similar devices on people. It does not apply to private home use.

NMES

Neuromuscular electrical stimulation, the clinical term for EMS applied to individual muscles, often in rehabilitation.

OTC and prescription use

An FDA clearance states whether a device may be sold over the counter to consumers or is for prescription use under professional supervision.

Pulse width (µs)

The duration of a single pulse in microseconds. Most research uses 350 µs.

Ramp

The time over which intensity rises at the start of each stimulation phase, which makes contractions feel smoother.

Rhabdomyolysis

Severe muscle breakdown that can harm the kidneys. In EMS it has occurred mainly after first sessions at too high an intensity.

Sarcopenia

Age-related loss of muscle mass and strength.

WB-EMS

Whole-body electromyostimulation: EMS applied to all major muscle groups at once through a suit or vest.

Wet electrode

An electrode, or an undergarment beneath it, that must be moistened with water before training to conduct well.

See these terms in use in how EMS training works and the buying guide.