Updated: Nov 17, 2019
One of the main issues that the Electrotherapy field has is basic terminology and frequency vs pulse is the example. I don't think a lot of players in the field are really clear either and unless you get background from other fields you don't see how deep the problem is.
Frequency is expressed in Hertz/ Hz and 1 hertz is a complete cycle of a positive going wave and then a negative going wave in 1 second of Time, both combine to make a complete +/ - cycle, the Ying & Yang symbol is a good example of a Hertz cycle.
The basic problem is that about the only common source of Hz energy is wall socket 117 VAC/ 60 Hz in the US, almost all other devices are just pulses of DC which end up labeled as Hz. The pulse width of a Hz cycle is 1/ frequency and each cycle consists of 2 pulses, + & - waves. So 60 Hz is 120 pulses, alternating between + and - pulses.
Let's look at TENS devices as they are well known. TENS devices are based on electrical pulses of microcurrent DC energy. They are in the 60 > 100 Hz and tend to be centered on the high end ~ 100 Hz in the US.
Note the highlighted 'Pulse' section under the High-TENS column. Here they show the actual pulse width which for a true 100 Hz wave would be .0083 seconds or 8300 microseconds not the 60 > 100 micro's shown under High-TENS/ Sensory.
TENS pulse programs consist of carefully profiled voltage spikes/ pulses. These pulses can be either polarity (they are DC not AC) and are often staggered so you might get 1 positive pulse followed by 2 negatives pulses as they mix up the program but the Hz rate remains the same as the number of pulses-per-second stays the same.
As with material processing, Bio-systems will react very differently to pulse profiles with the strongest effects coming from the faster pulses, square wave is much more influential than sine wave for example but the frequency remains the same.
At Earth's Glow, we use high voltage electrostatic energy because that will also pass thru the entire body like RF does. Static are fast fields like radio frequency waves but because they are basically voltage with extremely low current flow (inductance), they can flip polarity super fast across the entire body making them ideal when you want the fastest pulse rise time available without the transmitting issues with RF
So keep in mind when talking about frequency we need to be a lot more specific, it's at least as important to consider the pulse profile.