Manipulation of the Duration of the Initial Self-Control Task Within the Sequential-Task Paradigm: Effect on Exercise Performance

Fatigued or bored? Investigating the effect of different types of mental fatigue on 3 km running performance

Mental fatigue has been highly cited as having a negative impact on endurance performance. Few, however, have investigated whether different types of mental fatigue, namely active and passive fatigue, might affect endurance performance differently. This study used a repeated-measures design where 11 participants completed a 3 km run after three 32-min conditions: an actively fatiguing task (Task-load Dual-back; TloadDback); a passively fatiguing task (Mackworth Clock); and a control task (Documentary). Subjective ratings and performance on a second task (Flanker task) were taken before and after the 32-min tasks, while ratings of perceived effort, motivation and workload were taken during the 3 km run. Results showed that both fatigue conditions were mentally fatiguing, with the TloadDback rated as more demanding and the Mackworth Clock more boring and less motivating. Performance on subsequent tasks showed different effects: the TloadDback condition had the slowest responses on the post-test Flanker task, while the Mackworth Clock condition had the slowest completion time on the 3 km run, though this difference in completion times was non-significant. These results suggest that different cognitive tasks lead to different types of mental fatigue, which can lead to different outcomes on subsequent cognitive tasks but non-significant differences on subsequent physical tasks. This study highlights that to understand the influence of mental fatigue on physical performance, it is important to understand the cognitive tasks used and how different cognitive and physical tasks interact. Future work should examine whether performance outcomes in other areas commonly affected by mental fatigue, like technical and tactical sporting skills, are affected differently by active and passive fatigue.

Assessing the Evidential Value of Mental Fatigue and Exercise Research

It has often been reported that mental exertion, presumably leading to mental fatigue, can negatively affect exercise performance; however, recent findings have questioned the strength of the effect. To further complicate this issue, an overlooked problem might be the presence of publication bias in studies using underpowered designs, which is known to inflate false positive report probability and effect size estimates. Altogether, the presence of bias is likely to reduce the evidential value of the published literature on this topic, although it is unknown to what extent. The purpose of the current work was to assess the evidential value of studies published to date on the effect of mental exertion on exercise performance by assessing the presence of publication bias and the observed statistical power achieved by these studies. A traditional meta-analysis revealed a Cohen's dz effect size of - 0.54, 95% CI [- 0.68, - 0.40], p < .001. However, when we applied methods for estimating and correcting for publication bias (based on funnel plot asymmetry and observed p-values), we found that the bias-corrected effect size became negligible with most of publication-bias methods and decreased to - 0.36 in the more optimistic of all the scenarios. A robust Bayesian meta-analysis found strong evidence in favor of publication bias, BFpb > 1000, and inconclusive evidence in favor of the effect, adjusted dz = 0.01, 95% CrI [- 0.46, 0.37], BF10 = 0.90. Furthermore, the median observed statistical power assuming the unadjusted meta-analytic effect size (i.e., - 0.54) as the true effect size was 39% (min = 19%, max = 96%), indicating that, on average, these studies only had a 39% chance of observing a significant result if the true effect was Cohen's dz = - 0.54. If the more optimistic adjusted effect size (- 0.36) was assumed as the true effect, the median statistical power was just 20%. We conclude that the current literature is a useful case study for illustrating the dangers of conducting underpowered studies to detect the effect size of interest.

Effects of Stroop task duration on subsequent cognitive and physical performance

The strength model of self-control purports to explain why brief cognitive response inhibition tasks impair subsequent isometric handgrip endurance. According to the model, ego depleting tasks requiring self-control resources impair performance on subsequent tasks that also require self-control resources. However, several lines of evidence challenge this model, including evidence of improved exercise performance following longer cognitive tasks. Our study investigated the effects of cognitive task duration on (1) subsequent physical endurance performance, (2) concurrent cognitive task performance, and (3) subsequent novel cognitive task performance. Adopting an experimental design, with Stroop task type (incongruent, congruent) and duration (5, 10, 20 min) as between-participant factors, participants (N = 180) completed a color word Stroop task, an isometric handgrip to exhaustion task, and a novel 5-min incongruent number word Stroop task. In the handgrip task, endurance performance was worse following incongruent word Stroop than congruent word Stroop for 10-min tasks but not 5-min and 20-min tasks. In the word Stroop task, accuracy was lower and speed was slower following incongruent word Stroop than congruent word Stroop. Importantly, reaction times improved with longer task durations. In the novel number Stroop task, accuracy was higher following incongruent word Stroop than congruent word Stroop. In conclusion, the finding that the ego depletion effect was moderated by cognitive task duration is better explained by the expected value of control model than the strength model.

Cognitive tasks elicit mental fatigue and impair subsequent physical task endurance: Effects of task duration and type

Although mentally fatiguing cognitive tasks can impair subsequent physical endurance, the importance of cognitive task duration and the role of response inhibition remain unclear. This study compared the effects of a serial incongruent Stroop color-classification task (i.e., with response inhibition) and N-back memory updating task (i.e., without response inhibition) on mental fatigue and subsequent rhythmic handgrip exercise. Participants (N = 90) were randomly assigned to one of three cognitive task groups (Stroop, 2-back, control) and completed four 10-min blocks of one cognitive task followed by a 5-min physical endurance task (self-paced rhythmic handgrip exercise). Heart rate, heart rate variability, electromyographic forearm activity, and force were recorded throughout along with self-reported measures of fatigue, exertion, and motivation. From the start, the Stroop and 2-back tasks elicited higher heart rate and lower heart rate variability as well as greater fatigue, effort, and interest/enjoyment than the control task. From the second block onwards, the Stroop and 2-back groups produced less force than the control group. There were no group differences in forearm muscle activity. In sum, mental fatigue was induced after performing a cognitive task for 10 mins, whereas muscular endurance was impaired after performing a cognitive task for 20 mins. That these effects were observed for both types of cognitive task indicates that response inhibition is not a necessary condition. The cognitive task duration required to induce mental fatigue and impair rhythmic handgrip endurance performance lay between the durations reported previously for isometric (a few minutes) and whole-body (half an hour) endurance exercise.

Detrimental effects of prior self-control exertion on subsequent sporting skill performance

The prior exertion of self‐control has previously been shown to negatively affect physical performance, yet the effects on complex sporting skill performance have not been examined. Therefore, this study examined whether prior self‐control exertion influences performance on a field hockey task, alongside measuring plasma cortisol concentration and attention as potential mechanisms to explain any effects.

Following familiarization, 13 male hockey players (20 ± 1 years) participated in a randomized, order‐balanced, crossover design. For the manipulation of self‐control, participants completed an incongruent (self‐control exertion trial) or a congruent (control trial) Stroop task. Skill performance was assessed using a field hockey skills task. Capillary blood samples, for the determination of plasma cortisol concentration, were taken at baseline, post‐Stroop task, and post‐field hockey skills task. Cognitive tests of attention (RVIP and Flanker tasks) were completed following the field hockey skills task.

Participants made more errors in the latter stages of the field hockey skills task following self‐control exertion (trial*time interaction, p = 0.041). Participants also made more errors on the RVIP task following self‐control exertion (p = 0.035); yet the time taken to complete the hockey skills task, performance on the flanker task, and plasma cortisol concentrations were unaffected (all p > 0.05).

Overall, these findings suggest that prior self‐control exertion has detrimental effects on subsequent sporting skill performance (more errors made on the field hockey task), which may be explained by poorer sustained attention (lower accuracy on the RVIP task). This suggests that athletes should aim to avoid self‐control exertion before a competitive match to optimize performance.

Testing the Effects of a Preceding Self-Control Task on Decision-Making in Soccer Refereeing

The present study tested the assumption that the momentary level of self-control strength affects the accuracy rates in a sports-related judgment and decision-making task. A total of N = 27 participants rated the veracity of 28 video-taped statements of soccer players who were interviewed by a non-visible referee after a critical game-related situation. In half of the videos, the players were lying, and in the other half, they were telling the truth. Participants were tested twice: once with temporarily depleted self-control strength and once with temporarily available self-control strength (order counterbalanced; measurements separated by exactly 7 days). Self-control strength was experimentally manipulated with the Stroop task. In line with two-process models of information processing, we hypothesized that under ego depletion, information is processed in a rather heuristic manner, leading to lower accuracy rates. Contrary to our expectations, the level of temporarily available self-control strength did not have an effect on accuracy rates. Limitations and implications for future research endeavors are discussed.

A Primer on the Role of Boredom in Self-Controlled Sports and Exercise Behavior

Self-control is critical for successful participation and performance in sports and therefore has attracted considerable research interest. Yet, knowledge about self-control remains surprisingly incomplete and inconsistent. Here, we draw attention to boredom as an experience that likely plays an important role in sports and exercise (e.g., exercise can be perceived as boring but can also be used to alleviate boredom). Specifically, we argue that studying boredom in the context of sports and exercise will also advance our understanding of self-control as a reward-based choice. We demonstrate this by discussing evidence for links between self-control and boredom and by highlighting the role boredom plays for guiding goal-directed behavior. As such, boredom is likely to interact with self-control in affecting sports performance and exercise participation. We close by highlighting several promising routes for integrating self-control and boredom research in the context of sports performance and exercise behavior.