Lower than you think. The golden rule for EMS is to start well below your max and build up slowly.

For each muscle group, turn the intensity up only until you feel a firm, clear contraction that’s completely comfortable — you should still be able to move and talk normally. If it’s gritted-teeth intense, back it off. It’s normal for some areas (glutes, thighs) to take more and others (arms) to need less.

Give yourself an 8–10 week ramp-up at moderate intensity before chasing higher levels. This isn’t just about comfort — going too hard too early is the main way people get into trouble with EMS (see the pinned safety notice on rhabdomyolysis). Slow and consistent wins here.