Show me the money! Incentives attenuate effects of cognitive control exertion (mental fatigue) on physical endurance performance

  • Denver Brown Kinesiology, McMaster University
  • Steven Bray Kinesiology, McMaster University

Abstract

Exerting cognitive control results in fatigue that impairs subsequent physical performance. Motivational incentives have been found to reduce negative effects of cognitive control exertion on cognitive task performance, however these effects have not yet been extended to physical performance. The purpose of this study was to investigate the effect of monetary incentives on physical performance following exposure to a cognitive control challenge. Participants (N=61) performed two endurance isometric handgrip exercise trials (50% of maximum contraction) separated by a 10-minute cognitive control manipulation. Participants were randomized to one of three conditions: documentary watching (control), incongruent Stroop task or incongruent Stroop task with surprise monetary incentive offered prior to the second handgrip trial. Results revealed significantly greater mental fatigue following the Stroop conditions compared to controls. There were no between-group differences in task motivation prior to the second handgrip trial. The main analysis showed a negative carryover effect of cognitive control exertion on physical performance. Compared to controls (Mchange = -0.28), the no-incentive group showed performance impairment across handgrip trials (Mchange = -10.54), while the incentive group showed a slight performance advantage (Mchange = 3.86). Results demonstrate deleterious effects of fatigue can be counteracted by providing monetary incentives and may even facilitate performance compared to unfatigued controls. Brain regions responsible for effortful control show reduced activation following prolonged exposure to challenging cognitive tasks, however motivational incentives restore activation within these regions. Increased central activation may help energize volitional action or over-ride feelings of fatigue to support enhanced performance of effortful tasks, regardless of the nature of the task.