Fatigue analysis of the flexor digitorum superficialis muscle using mechanomyogram during moderate-intensity intermittent dynamic tasks

The capabilities of multidimensional mechanomyography (MMG) via PVDF sensors were explored to characterize flexor digitorum superficialis (FDS) fatigue during a 30% MVC, 1 Hz dynamic grasp task-representative of industrial activities yet underexplored in MMG research. This study aimed to delineate fatigue progression, evaluate 30-second micro-rest efficacy, and elucidate gender/hand dominance differences, rationale being their known influence on neuromuscular control and fatigue resistance, with FDS-specific responses in this context unclear. Twenty-four healthy right-handed subjects (12 males, 12 females) completed the task, with MMG and Borg CR-10 data collected. Significant fatigue was confirmed via 19.7% MVC decline and 15-fold Borg score rise. MMG analysis revealed IMMG reduction, while frequency (e.g., MPF) and nonlinear (e.g., LLE) features showed group effects. Muscle contraction rise time correlated strongly with MVC decline and Borg scores, emerging as a potential fatigue indicator. Females exhibited greater MVC reduction, higher Borg scores, and unique sample entropy responses; non-dominant hands showed faster perceived exertion increases. Micro-rests were insufficient for recovery. These findings clarify MMG dynamics in dynamic fatigue, address gaps in FDS individual variability research, and inform personalized assessment and ergonomic interventions.