Development of a new, non-invasive and at real-time modality, to identify athletes’ fatigue during exercise is important for performance enhancement and to avoid over-training and exercise-related injuries. Despite the increasing interest in facial expressions for fatigue evaluation, and the great potential of facial surface electromyography (sEMG) signals in quantifying fatigue-related outcomes, this topic has not been widely studied, apparently due to a technical gap in sEMG technology that limited both convenient and accurate measurements. Recently, a novel sticker sensor of multiarray conductive electrodes was introduced and was used for long-term recording in freely behaving humans and for mapping spontaneous smiles. The aim of Rawan's thesis is to analyze facial muscle activity patterns using a high-density electrodes sticker, for fatigue evaluation during aerobic exercise until exhaustion.