Short answer: it shouldn't hurt. A good session feels like a strong, involuntary tightening or a deep tingle that comes in waves — the muscle grips during the impulse and relaxes between. That can feel intense, especially as you turn it up, but it's a "whoa, that's a lot" feeling, not pain.

What's not normal: sharp, stabbing, or burning sensations, or stinging at a single spot. That usually means the intensity is too high or an electrode isn't making good contact — turn it down and check placement. Mild redness afterward is common and fades within an hour.

If you ever feel faint, or get severe pain, weakness, or dark urine in the days after a session, stop and see a doctor — see the pinned safety notice on rhabdomyolysis.