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Harvard Medical School
For the EMG, thin needles are inserted one by one into the muscles being tested. These needles are not hollow, and they are thinner than the type of needle used to draw blood. Each needle is attached to a wire that gives signals to a machine. The needle acts like an antenna to detect electrical patterns inside the muscle and the nerves that are attached to that muscle. Most patients find this test mildly uncomfortable.
If you have nerve conduction studies done, small pads are taped to the skin on your hands or feet. These pads can both deliver mild electric shocks and detect electric signals coming through the skin. The shocks that are used are too small to be harmful. They feel similar to the kind of shock you might feel if you rubbed your feet on the carpet and then touched a doorknob. You might feel one of your muscles twitch when the electricity is delivered.
Testing times vary, depending on how many muscles are being tested. EMG testing takes 20 to 30 minutes. If nerve conduction studies are also done, testing may require as long as one hour.