Relationship between the level of mental fatigue induced by a prolonged cognitive task and the degree of balance disturbance

A study led by Frédéric Noé and colleagues from MEPS, DevAH, ISM, and LMAP investigated how mental fatigue from a prolonged cognitive task impacts balance control. Twenty healthy young participants completed a 90-minute AX-continuous performance test (AX-CPT), a demanding cognitive task. Balance was measured before and after on a force platform with eyes open and closed. The NASA-TLX test assessed subjective fatigue, while cognitive performance was tracked via AX-CPT results.

Hierarchical cluster analysis revealed significant inter-individual differences in mental fatigue levels and balance impairments. A clear relationship emerged: higher mental fatigue correlated with greater balance disturbance, but only when participants stood with eyes open. This suggests that visual attention engagement and field dependency—how individuals rely on visual cues for balance—mediate the effect. The findings underscore that even identical cognitive tasks produce heterogeneous physical responses, with implications for safety in tasks requiring steady posture, like driving or operating machinery.