Abdominal Muscle Training with EMS Fitness Equipment1. USB charging: built in Li ion battery rechargeable by USB and USB cable included, which not only reduces the cost of frequent battery replacement, but also protects the environment. The intensity of machine exercise increases by 50% compared to battery powered products. Fully charged in 1 hour, you can get continuous work for 3 to 4 hours, you can charge this muscle stimulator with your laptop or 2. Fat burning and toning the muscle and body