Nerve ; muscle test. Emg/ncs is a test that uses small electric shocks along nerve tracts, and needles into muscles.. While small nerve fibers cannot be accurately tested, middle and large nerves will demonstrate changes in transmission times and rhythm. Muscle, will demonstrate changes in wave form, and resting potential. Neuropathy, polio, myopathy, radiculopathy, entrapped nerves, carpal, cubital/ carpal tunnel, .