I haven’t tried it enough to say what number is optimal yet.
For example, if you shorten the rest, albeit with active recovery added, you will be fine for a set number of reps but might find additional fatigue after that starting number.
So you might start with a maximum of 10 reps, counting on the shorter contraction times to compensate for the shorter rest and move to 15 once you can determine that:
A: You have no training losses elsewhere in your training program
B: The intensity of the contraction remains high to the last rep you use.
Another option is to divide the EMS sessions in a day, divided by 4 hours. IE 2 set of 6 or 3 sets of 5, basically whatever you want.
This is very handy when recovering from an injury that limits other training and we have done this at times .
There is no reason why you can’t be as flexible with the use of EMS as you would be with other training modalities, keeping in mind that you are sparing the nervous system compared to other methods.