The harmful EMF's, which most countries have pased strict testing regulations around, are the continous hi frequency fields generated by what are called "switched mode power supplies" which are found in just about all electronic appliances, due to their low weight and low cost compared to convention transformers. These generate frequencies from usually 30 - 40Khz and up to the radio band. The clock frequencies of computers and micro-controller chips also fall into this frequency ranges higher end at 4Mhz up. Basically any device using switching frequencies above 1000 hertz should be tested for EMF emission, (incedently the US has the lowest standards in the world in this) and it can be a very long drawn out and expensive process. So few of the back yard guys have tests done.
The pulse applied to the body by a true Beck Pulser is DC, but the box containing the power supply will emit EMF to some degree. SOTA quite wisely used to advise keeping the electronics away from the body. Their latest offerings are tested to the European CE* standards which includes EMR testing. The 5K Oscillating pulsers should be treated similarly only more so, these use a very hi voltage switch mode supply and I would expect the EMF to be much higher, and it's output is almost pure AC harmonics.
If your muscular problems are due to inflamation, the Beck type pulser will definitely help.
*(regarded by most Europeans as standing for "Chinese Export")