Biofeedback technique consists in the real-time provision of physiology-related information acquired from an individual, as an extension of his intrinsic sensorial feedback. The use of EMG-based biofeedback in sport and rehabilitation contexts has been widely investigated at research level and nowadays it is considered having a great potential in influencing voluntary muscle activation. Consequently, it may be used as a promising treatment for a broad range of musculoskeletal conditions. Traditionally, biofeedback has been delivered in real-time through simple visual indicators, acoustic, or vibrotactile stimuli. The recent development of Augmented Reality (AR) technologies constituted the technological premise allowing the use of this technique in the sEMG biofeedback field.