MULTİDİMENSİONAL ASSESSMENT OF MUSCLE FATİGUE İN SOCCER PLAYERS

Overview

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.

Muscle fatigue is commonly assessed using surface electromyography (sEMG), particularly through frequency-domain parameters such as median frequency. However, fatigue-related changes are not limited to electrical activity and may also involve alterations in muscle mechanical behavior and morphological characteristics. Accelerometer-derived signals provide information regarding muscle vibrations and mechanical oscillations, while ultrasonographic measurements of muscle thickness provide information about muscle morphology and force-generating capacity. The purpose of this study was to examine the relationships among muscle thickness, sEMG median frequency, accelerometer-derived mechanical vibration parameters, and isometric force variables during maximal voluntary isometric contractions performed at different knee flexion angles. Healthy male soccer players participated in a laboratory-based assessment protocol including ultrasonography, synchronized sEMG recordings, triaxial accelerometry, and isokinetic dynamometry. Muscle thickness of the vastus lateralis obliquus (VLO), vastus medialis obliquus (VMO), and rectus femoris obliquus (RFO) muscles was measured using ultrasonography. Participants subsequently performed maximal voluntary isometric contractions at 90°, 60°, and 30° knee flexion angles. Surface electromyography, accelerometer signals, and force-related variables were recorded simultaneously. Median frequency values, acceleration-based root mean square (RMS) parameters, peak torque, mean torque, and time-to-peak torque variables were analyzed. The study aimed to provide a multidimensional framework for muscle fatigue assessment by integrating morphological, electrical, and mechanical indicators and to explore their associations in healthy athletic populations.