Electromyography (EMG)

Nerves run from our spinal cord to our muscles and transmit the signals from the brain for muscle contraction.  When a nerve stimulates a muscle, a small amount of electricity is produced on the muscle cell membrane which can be measured at the surface of the skin overlying the muscle.  As the desired force of muscle contraction increases, the amount of electrical activity also increases. This is evident in the figure to the left which shows what happens to the electromyograph as more and more force is required.  The red data to the left demonstrate an increase in the "raw" EMG signal and the green line is a graphical view of EMG activity.