The impulses are generated by a device and delivered through electrodes on the skin in direct proximity to the muscles to be stimulated. The impulses mimic the action potential coming from the central nervous system, causing the muscles to contract. The electrodes are generally pads that adhere to the skin. The use of EMS has been cited by sports scientists as a complementary technique for sports training and published research is available on the results obtained. In the United States, EMS devices are regulated by the U.S Food and drug administration (FDA).