EMG
Muscle sensors, like these electromyography (EMG) sensors, work by reading the tiny electrical signals your muscles make when they move, a process called "surface electromyography" (sEMG). When you decide to flex those muscles, your brain sends a signal to wake up your "motor units" which are the bundles of fibers that do the heavy lifting. Flexing harder forces more of these units into action, which creates a larger electrical signal. These sensors read this electrical activity and turns it into a measurable voltage, so the harder you flex, the higher the voltage output from the sensor!
