Is intense physical exercise detrimental for cognition? A novel approach based on subjective, behavioral and physiological responses to a cognitive effort to failure

Abstract

Most previous research has investigated whether performing a demanding cognitive task reduces the time a person can hold a subsequent physical effort. However, no previous research has investigated if performing an intense physical exercise reduces the time a person can complete a cognitive task with an adequate level of performance. The aim of this study was to assess the subjective, behavioral and physiological responses of performing an intense physical exercise on a posterior cognitive tak until failure. In a pre-registered, randomized, within-participant design experiment, 29 physically active participants completed a cognitive task until failure after running at 90% maximal aerobic speed until failure or after walking for 10 min (control condition). During the cognitive task, brain activity was recorded with an electroencephalogram and brain complexity was quantified. Multidimensional subjective experience was assessed with the Temporal Experience Tracing method (TET). Sequential Bayesian analysis for the main hypothesis (intense physical exercise reduces cognitive task performance) until it reached strong evidence in favor of the alternative hypothesis (BF10 > 6) or the null hypothesis (BF10 < 1/6) were conducted. The physical exercise induced a reduction in maximal force generating capacity and increased rate of perceived exertion compared to the control condition, evidencing the strong differences in physical workload between conditions. The total duration to complete the cognitive task in both conditions were 4755.8 s (95% CI 3326.8 - 5107.8) and 4308.2 s (95% CI 3902.9 - 5481.2) for the control and experimental conditions, respectively with no evidence of difference across sessions (BF10 = 0.329). Subjective experience analysis identified two distinct clusters of task-related demands, but the time spent in these experiential states did not differ between conditions. However, cognitive task performance was better in the phases of low perceived demands. Brain complexity was lower after the maximal aerobic speed effort, indicating a potential shift in physiological states, although neither behavioral (cognitive) performance nor subjective feelings were affected.