Facial Lower-Region Changes During High-Intensity Exercise as Predictors of Reduced Arousal State

This study examined whether facial muscle movement changes during incremental exercise testing are associated with mood indicators related to executive function. Twenty-five male university students performed incremental cycle ergometer test. Facial expressions were recorded and analyzed using Py-Feat to detect Action Units (AUs), while heart rate, blood lactate concentration, rating of perceived exertion (RPE), and the Two-Dimensional Mood Scale were measured. Generalized additive mixed models were used to examine the relationships between 16 AUs and physiological/psychological indicators, and correlation analysis assessed AU changes across exercise intensity transitions. Exercise intensity-dependent changes were observed in numerous AUs, with AU10 (upper lip raiser), AU17 (chin raiser), AU25 (lips part), and AU26 (jaw drop) demonstrating strong correlations with exercise load, heart rate, blood lactate, and RPE (r = 0.314-0.631, all P < 0.05). During the transition from moderate to high intensity, AU25 changes were significantly negatively correlated with arousal changes (r = -0.436, P = 0.029). These findings indicate that facial expression changes, particularly AU25, serve as reliable indicators of physiological and psychological responses during exercise. They also support the inverted-U hypothesis of arousal and highlight facial expression analysis as a promising non-invasive tool for exercise monitoring and cognitive function optimization.