Multimodal assessment of exercise-induced fatigue: integrating cardiopulmonary, neuromuscular, and biomechanical profiling in high-intensity running.

This study aimed to establish a multimodal framework integrating cardiopulmonary exercise testing (CPET), surface electromyography (sEMG), and plantar kinetic assessment to characterize neuromuscular and mechanical fatigue responses during high-intensity treadmill exercise. Twenty healthy collegiate male athletes performed an incremental CPET followed by a supramaximal verification phase. Gas exchange, heart rate, and perceived exertion were continuously recorded. Bilateral sEMG activity from the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius lateralis was analyzed for integrated EMG (iEMG), root mean square (RMS), and median frequency (MF). Pre- and post-exercise plantar kinetics were obtained using in-shoe pressure sensors to assess contact area, mean pressure, and vertical ground reaction force (VGRF). Plantar kinetics showed increased midfoot contact area (+12.3%, P = 0.01) and pressure (+10.8%, P = 0.03), along with elevated left-foot regional VGRF (P = 0.04), indicating side-specific post-exercise load redistribution. Although nominal correlations were observed between neuromuscular activation and post-exercise plantar loading, these associations did not remain statistically significant after false discovery rate (FDR) correction and should therefore be interpreted as exploratory. Rather than establishing a quantitative diagnostic threshold for fatigue, integrating cardiopulmonary, neuromuscular, and plantar kinetic measures contributes to a multidimensional characterization of fatigue-related adaptations beyond metabolic indicators alone. This multimodal framework illustrates how neural drive decline and mechanical load redistribution may co-occur under acute fatigue conditions, providing a structured approach for comprehensive fatigue profiling in athletic populations.