EMS stands for electrical muscle stimulation; in training, a machine delivers electrical pulses that stimulate muscle contraction. If you’re thinking, “But wait, electrical impulses in the body already stimulate muscular contraction. It’s called action potential!” you are correct. But EMS heightens those contractions, intensifying your workout in a way that your body could not on its own.
It makes your exercise even more challenging and can help you burn more calories. A Wall Street Journal reporter said it made her four-pound weights feel like 20 pounds.