Mbloom,
I do not have a direct answer for you, but only additional comments on the physiology of EMS, adding some detail to what is going on:
[ul]
[li]As more blood circulates through the muscles, the resistance to current of the muscle decreases, therefore you need more a little more current to trigger and fire the motor-neurons;
[/li][li]As motor-neurons get fired, especially if they get fired a lot, as in a max. strength protocol, they are subject to fatigue, meaning they have a little less at their disposal to trigger their effect
[/li][li]Same as above is valid for pain and tactile neurons, therefore you have a decreased feeling of pins and needles; make sure not to confuse lees feeling for less contraction.
[/li][li]Similarly as above there is nerve accommodation to the electrical signal sent through it; the two mechanisms above are in effect part of accommodation, but there probably are other nervous system factors at play.[/ul]
[/li]Last comment: wow 120 mA … that’s a lot of juice!