The BodyMed Analog EMS Unit is an Electrical Muscle Stimulator for home / personal use. By definition EMS units work by sending weak electrical impulses to stimulate your target muscles, causing them to contract and relax. They replicate the signal the brain usually sends to muscles during exercise. EMS Units like the BodyMed Analog EMS Unit have been used to treat certain medical conditions, such as muscle atrophy, muscle spasms and decreased range of motion. The BodyMed Analog EMS Unit features a protective cap over the amplitude adjustment knobs to prevent unintended changes to the pulse amplitude.