EMS problem

I noticed that above 50 Hertz of ems rate, my skin is getting fried and the feeling of electricity rather than contraction takes over.

Is this normal ? I would really like to work at 100-150 hertz like it says on the articles but I just can’t… whats going on ? Why does it happen ?

I am not sure 50z is so good because the contraction is so deep and so intense that the muscle was extremely sore the following day…

It all depends on your mA current intensity and pad position. But if you have a cheap unit you won’t be able to improve things much.