Charlie in his book explain that with ems you can work on foot strenght, but when i Try to use ems on my feet, i can’t use it.
i have compex 500. how can i use it on my feet (pad position and so on)
WHY can’t you use it? I did it for the first time with my new machine and it worked fine, other than hurting like (#$&)(&. 
John
where do you put the red one (+ positive) and theblack one (- negative)?
i tryed it,but I feel a lot of electricity, a lot of pain, but no movement at all of muscle.
Make sure your foot is clean and free of oils and that the pads are in full contact with the foot, front and back. If you have a traditional pad rather than a sticky pad, perhaps a damp sponge on the pads will ensure full contact. Experiment a bit.
Use small pads or cut them for this kind of stimulation, then + and - aren’t important because EMS use alternate current and the pads are alternatively positive and negative.
Generally don’t put them on heel and try to work on frequency and not only on placement.
Experiment, Charlie docet!!!
I don’t use the sticky pads, but I use some water to get them damp before placing them on the ground (damp side up) then stand on them. One pad goes right in front of my heel, the other just behind the ball of my foot.