Electromyogram (EMG) and Nerve Conduction Studies. Guide. An electromyogram (EMG) measures the electrical activity of muscles at rest and during contraction. Nerve conduction studies measure how well and how fast the nerves can send electrical signals.Nerves control the muscles in the body with electrical signals called impulses.n EMG is done to: 1  Find diseases that damage muscle tissue, nerves, or the junctions between nerve and muscle. 2  Find the cause of weakness, paralysis, or muscle twitching.