The EMG-based biofeedback device is a tool to provide a vibration proportional to the activation of a particular target muscle. It has been developed by the SangerLab and it has been designed to be wearable, so it consists of an SX230 active differential electrode (Biometrics Ltd, Ladysmith, Virginia; bandpass filter 20-460 Hz, amplification 1000x, 10 Mohm input impedance) with an additional custom circuit board that includes a 50 MHz microcontroller (Analog Devices, Norwood, Massachusetts, USA, ADUC7020), custom circuitry variable gain amplifer (0.03 to 30x secondary amplification), and a vibration motor (C1234B016F, Jinlong Machinery, Zhejiang, China, 80-100 Hz vibration). When used as a portable device, the motor is driven through a power MOSFET by a pulse-width modulated signal from the microcontroller. The microcontroller communicates by TTL-level serial lines to the belt pack, which contains a 2000 mAh lithium-ion battery, battery charging circuit (BQ24200, Texas Instruments Inc., Dallas, Texas, USA), and a Bluetooth serial port (ESD200, SENA Inc., San Jose, California, USA).