For building strength and muscle in general (non-athlete) populations: yes, and it’s reasonably well supported. A meta-analysis of controlled trials found significant, meaningful gains in muscle mass and strength from WB-EMS. There’s also decent evidence it helps nonspecific chronic back pain and benefits older adults, partly because it’s low-impact.

Where the evidence is weaker or absent: fat loss (no reliable effect on its own), and the dramatic marketing claims (“melts fat,” spot-reduction, exact muscle-fiber percentages).

Fair summary: the core thing EMS is sold for — time-efficient strength and muscle — holds up. The hype stuff doesn’t. Judge it by the former and it’s a genuinely useful tool.