Non-invasive Evaluation of Muscle Fatigue Using Mechanomyography and Surface Electromyography - A Pilot Study

Muscle fatigue is defined as a decline in the ability to maintain a desired force against a load. Muscle fatigue may also be described as a decline in the muscle's maximum force during contraction. In contrast to muscle damage or weakness, characterized by a compromise in the ability of well-rested muscles to generate force, muscle fatigue is generally reversible with rest [2]. In a muscle experiencing fatigue, the nerves cannot sustain the high frequency signal necessary to reach the Maximum Contraction (MC) for a long time, resulting in a decline in muscle force during a sustained contraction. Due to its utility in providing information about nerve signaling and muscle's electrical activity, surface electromyography (sEMG) is currently the dominant method to detect muscle fatigue [2]. Mechanomyography (MMG) can reveal unique information that cannot be derived from the sEMG signal alone about the physiological behavior of muscles during contraction. However, more information may be needed about the ability of MMG to measure changes in muscle's activation patterns and mechanical properties that occur with muscle fatigue. Additionally, investigating the force-dependent characteristics of the MMG signal can provide information about physiological properties such as muscle activation strategies and fiber type distribution, which can be used to explore factors contributing to fatigue responses [1]. The purpose of this study is to examine and analyze the electrical and mechanical muscle responses to submaximal isometric contractions, as well as force-varying trapezoidal contractions in the rectus femoris muscle.