Muscle fatigue is a multifactorial physiological phenomenon characterized by a reduction in the ability of a muscle to generate force during sustained or repetitive contractions. This cross-sectional observational study aimed to investigate the relationships among muscle thickness, surface electromyography (sEMG) median frequency, accelerometer-derived mechanical vibration parameters, and isometric force characteristics in healthy male soccer players. Thirty participants aged 18-30 years underwent ultrasonographic muscle thickness assessment, synchronized sEMG and accelerometer recordings, and isometric strength testing at different knee flexion angles (90°, 60°, and 30°). The study evaluated the interaction between morphological, electrical, and mechanical indicators of muscle fatigue to support the development of multidimensional fatigue monitoring approaches.