By Jedd Thorderson, PT, MPT, ECS
As I have had the opportunity to perform EMG and Nerve Conduction Studies over the past several years, I am often in awe of how all of this could have come to be. Who thought it would be a good idea to stick a needle into someone’s muscle, and did they really think they would hear something? Even once they heard the noises produced by a muscle, did they truly believe they knew what each of those sounds meant? Electromyography (EMG) and Nerve Conduction Studies (NCS) are now routine tools in the use of diagnosing many different things related to nerves and their functions, but how did it all begin?
The origins trace back to Luigi Galvani in the late 18th century. In 1771, Galvani observed that frog muscles twitched when touched by a charged scalpel, leading him to propose the concept of animal electricity — the idea that nerves transmit electrical signals to muscles. His work laid the foundation for modern neurophysiology. Throughout the 19th century, people like Matteucci, Duchenne, and Marley began to record electrical signals and map muscular responses to electricity, coining the term electromyography. Their discoveries established that muscle and nerve function could be measured electrically.
In 1922, the Nobel Prize was awarded to Erlanger and Gasser for their work recording action potentials in nerves and linking the velocity of the signal to the diameter of the nerve fiber. By 1925, Sherrington and Liddell would define a central concept to EMG interpretation by defining a motor unit as a single motor neuron and all the muscle fibers it innervates. Technology would continue to advance, leading to the oscilloscope and needle electrodes, allowing researchers to visualize individual motor unit action potentials, the signal generated by the contraction of all the muscle fibers innervated by a single motor neuron.
Emerging in the 1930’s was the EMG’s ability to diagnose certain nerve conditions, and by the 1950’s, the beginnings of what we know today as modern nerve testing began to be formed. Technology continues to improve, and with it has come standardization of testing and normative values and special techniques that allow the trained clinician to evaluate and diagnose neuropathies, radiculopathies, myopathies, and neuromuscular junction disorders.
The story of EMG and NCS reflects the beauty of curiosity-driven science with clinical necessity. What began as an exploration of “animal electricity” now guides the diagnosis and treatment of millions of patients worldwide. As technology continues to advance, EMG and nerve conduction testing will only grow in precision and impact. So, when you go for your EMG and nerve conduction testing, take heart that this is not some crazy thing meant only to shock you and jab you with a needle, but this is a science that has been refined over centuries.
