A Standardized Methodology for EMG-Based Fatigue Assessment during Electrical Muscle Stimulation

Abstract

This study presents a methodological framework for standardized electromyographic (EMG) fatigue assessment during electrical muscle stimulation (EMS), with a focus on M. biceps brachii. Based on existing literature, a protocol was developed and iteratively optimized through controlled trials. The approach addresses open research questions related to the complex interplay of physiological and technical factors in EMG-EMS measurements. Results demonstrate that individual motor threshold is the most appropriate parameter for normalizing EMS intensity in the context of pain-free fatigue measurements. Furthermore, arm positioning was identified as a critical factor for obtaining reliable M-wave recordings and artefact-free force signals. The findings underscore the necessity of high methodological standardization to reduce variability and improve the comparability of EMG-based fatigue metrics. Key requirements include the definition of objective and interindividually comparable stimulation intensities, as well as the application of protocols capable of inducing muscle fatigue without exceeding individual pain tolerance. The proposed framework provides practical guidance for reproducible data acquisition in EMS research and supports the development of objective, EMG-based monitoring approaches.