Graded Increases in Cognitive Control Exertion Reveal a Threshold Effect on Subsequent Physical Performance

Exertion of cognitive control is associated with subsequent impairment of physical performance, however, current understanding is limited because manipulations have involved either high or low cognitive demands. The purpose of this study was to investigate the effects of graded exposure to cognitive control on subsequent physical performance, while also examining psychological processes that may mediate this relationship. Participants (N = 123) performed 2 isometric handgrip endurance trials separated by a cognitive control manipulation (Stroop task). Participants were randomized to 1 of 6 conditions: 0, 2, 4, 6, 8, or 10 min of exposure to the Stroop task. All manipulations were presented in a fixed, 12-min testing window. The cognitive task occupied the full window in the 10-min condition and the latter 2, 4, 6, or 8 min of the window in the other conditions, with a mild-attention task performed prior to the cognitive manipulation. The testing window consisted of 2-min blocks of the Stroop/filler task separated by 30-s rest periods in which affective valence and mental fatigue were assessed. Results showed handgrip endurance performance was uniformly unaffected following 0 to 4 min and uniformly impaired following 6 to 10 min of exerting cognitive control. Mental fatigue, affective valence and task self-efficacy were correlated with both cognitive control exertion and endurance performance, however task self-efficacy was the only mediating variable. Results are the first to show a negative carryover effect from cognitive to physical tasks occurs at a threshold between 4 and 6 min of cognitive task exposure.