Effects of mental fatigue and attentional focus on muscular endurance performance

Mental fatigue shows consistent detrimental effects on physically-demanding tasks including running and muscular endurance tasks. Several strategies to mitigate these effects have been assessed; however, it is also important to explore factors that may combine with mental fatigue to amplify performance decrements. The present study investigated potential moderating effects of attentional focus on the mental fatigue - endurance performance relationship. Undergraduates (N = 78) completed two wall-sit tasks to volitional failure prior to, and following, a cognitive task. Using a 2 X 2 randomised factorial design, half the participants completed a mentally fatiguing cognitive task (incongruent Stroop; HF), while the other half performed a non-mentally fatiguing task (documentary viewing; LF). Prior to the second wall-sit task, half the participants in each of the HF and LF groups were given attentional focus instructions to focus internally (INT) and the other half to focus externally (EXT). Both the mental fatigue (p < .001) and attentional focus (p < .001) manipulations were found to be successful. Planned comparisons showed no significant effects of attentional focus or mental fatigue on wall-sit endurance performance. However, a large effect size was observed between the HF/INT group and the other three groups (d = -1.56). Overall, data indicate a potential moderating effect of attentional focus such that internal focus and high mental fatigue may combine to have detrimental effects on physical endurance performance.