Controlling our resources: Does cognitive depletion impair physical performance?


Strenuous physical exercise and challenging mental tasks require substantial self-control over effort and attention. The strength model proposes that self-control is a limited resource that governs control over behaviours, thoughts, and emotions. Expenditure of resources on an initial self-control task typically leads to a carryover effect of reduced performance on subsequent self-control tasks. Few studies have investigated carryover effects of self-control depletion on effortful exercise. Marcora et al. (2009) showed reductions in endurance cycling performance following 90 minutes of demanding cognitive tasks.  However, self-control depletion can be induced within minutes using tasks with high self-control demands. This study investigated the carryover effects of a demanding cognitive self-control task on performance of a graded exercise test (GXT) to voluntary exhaustion. Using a randomized crossover design, we tested the hypothesis that there would be a reduction in time to exhaustion on the GXT after completing a high-demand self-control task (stop-signal task [SST]) compared to a low-demand control task (watching a brief documentary).  Participants (N =8 males; 17-25 years) performed a baseline GXT on a cycle ergometer preceded by either the SST or control task. Seven days later, they completed a follow-up GXT preceded by the alternate self-control task. Participants reached voluntary exhaustion on the GXT faster after completing the SST (433.25 ± 110.28s) compared to the control condition (450.88 ± 101.81s) (P < .01). These results support the strength model of self-control and suggest there are common brain-based mechanisms that are taxed by cognitively- and physically-demanding tasks. Results are discussed in terms of limited resource and motivational interpretations.  Findings may have important implications for athletes’ training and pre-competition strategies.  Future research should consider how the type and duration of cognitive and exercise tasks affect the rate and extent of self-control depletion as well as the time it takes to replenish self-control resources.