Psychophysiological, subjective and physical responses to an individualized cognitive effort to failure

Over the past two decades, the interplay between cognitive tasks and physical performance has drawn increasing attention, with research suggesting that engaging in cognitive effort prior to exercise can impair subsequent physical performance due to heightened mental fatigue. However, recent studies have cast doubts on the robustness of this effect, prompting for a reassessment of the mechanisms underlying cognitive fatigue and its impact on physical performance. In this study, we present a novel approach aimed at addressing methodological limitations in prior research, with a focus on individualizing cognitive task difficulty and duration. By integrating innovative techniques such as Temporal Experience Tracing (TET) and psychophysiological monitoring, we sought to unravel the complex dynamics between cognitive engagement, subjective states, and physical performance. In a pre-registered (https://osf.io/8rkxq/), randomized, within-participant design experiment, 21 recreational athletes completed a running task to failure test at 90% of their maximal aerobic speed after performing a cognitive task until failure or watching a self-selected documentary (control). Six different subjective dimensions were recorded with the TET and pupillometry was recorded during cognitive task performance. The key findings of this study were: 1) subjective changes during effortful tasks are not limited to a single experience, such as mental fatigue or boredom, but can be grouped into distinct patterns; 2) despite the individualized and demanding cognitive tasks, completing them before exercise did not impair subsequent physical performance; 3) pupil size reliably reflected cognitive task performance until failure and partially reflected changes in subjective states, while fixation on the stimulus decreased over time, especially during high-demand periods. These results provide a new approach for understanding physical and behavioral responses, with implications for psychology and sports science.