Fluctuations in alertness and physical arousal levels occur naturally throughout the day, spanning from sleep to intense physical exertion. These changes unfold in a nonlinear manner, affecting cognition and the processing of exogenous and endogenous stimuli. A recent study (Canales-Johnson et al., 2020) found that the classical behavioural markers of conflict processing and conflict adaptation were intact in drowsy participants performing a Simon Task (Simon & Rudell, 1967). On the other hand, conflict processing on midfrontal (MF) theta-band power (a neural marker of cognitive control) was not detected in drowsy participants either using univariate or multivariate analysis. However, these effects were captured when looking at long-distance theta-band information sharing, reflecting the rise of a more distributed network. The disappearance of theta power differences driven by conflict processing and the reappearance of such effect in measures of long-range connectivity suggest the reorganisation of brain networks under reduced alertness. Regarding conflict adaptation, which reflects cognitive flexibility, there was no modulation of the effect by arousal level. In the present study, we will measure electrocenphalograpic (EEG) activity of conflict resolution during physical exercise to test the opposite end of the arousal spectrum: how high (physical) arousal affects cognitive control. It has been suggested that physical arousal level induced by exercise does not impact performance in cognitive control tasks. This appears to be the case particularly when the cognitive task is performed during acute exercise (Chang et al., 2012) and when the experimental design is controlled for dual task effects (ie when high intensity is compared to low intensity rather than no exercise; Moreau & Chou, 2019). Specifically, an experiment implementing the Simon Task during acute exercise found that conflict processing at the behavioural level was not modulated by physical arousal (Davranche et al. 2015). Taken together, these studies suggest a parallelism between the behavioural outcome of cognitive control at high-arousal and those observed in the drowsy state. Therefore, we aim to conceptually replicate the results in the drowsy state of Canales-Johnson at al.(2020) with participants that are instead pushed to a strain state of high arousal. Participants will be presented with an auditory conflict task while pedalling on a stationary bike. Arousal levels will be modulated by the intensity of the exercise determined as low-intensity and high-intensity. The level of effort will be individualised across participants based on their aerobic fitness level. We will analyse the conflict effect whereby conflicting information produces slower responses and greater midfrontal theta power compared to nonconflicting information. Similarly to Canales-Johnson et al.(2020), the effect of physical strain on cognitive control will be investigated across several measures: reaction times, error rates, midfrontal theta analysed with univariate and multivariate methods, and theta long distance information sharing. We will also look at conflict adaptation, which represents the modulation of the conflict effect in relation to previous conflict and that it is considered a measure of cognitive flexibility. A recent study has suggested that under physical strain individuals tend to employ volatile decision-making strategies at the cost of strategies relying upon cognitive flexibility (Ciria et al., 2021). Therefore, in contrast to the results of Canales-Johnson el al.(2020) we are expecting a modulation of the conflict adaptation effect by physical arousal in behavioural data. Prior to the preregistration, we ran a pilot study with 9 …