Mobile EEG in Ultramarathon Research using X.on and PEER

This article is based on the peer-reviewed publication:
Boere, K., Young, N. P., Copithorne, F., Dauphinee, R., Heath, M., Kirby, B. S., & Krigolson, O. E. (2025). Ultramarathon racing elicits changes in behavioural and electroencephalographic indices of executive function. Journal of Applied Physiology. https://doi.org/10.1152/japplphysiol.00941.2025

Ultra-endurance races such as trail ultramarathons place extraordinary demands on the human body, but they also place sustained demands on the brain (Hyland-Monks et al., 2018; Berger et al., 2023). Over many hours of running, athletes must continuously regulate pacing, interpret internal signals such as fatigue and thirst, adapt to changing terrain and weather, and make rapid decisions about fueling, hydration, and effort allocation (Pageaux, 2014). These processes rely heavily on executive function, the set of cognitive processes—including working memory, inhibitory control, and cognitive flexibility—that work together to support goal-directed behaviour (Diamond, 2013).

Despite growing interest in the role of cognitive processes during endurance performance, studying the brain at real-world ultra-endurance events has historically been difficult. Traditional electroencephalography (EEG) systems are designed for laboratory environments with shielded rooms, stable temperatures, seated participants, and tightly controlled experimental timing. Ultramarathons, by contrast, unfold outdoors across rugged terrain and variable weather, with athletes arriving exhausted, dehydrated, and time-constrained. To bridge this gap, we set out to test whether mobile, research-grade EEG could be deployed at the start and finish line of ultramarathon races without compromising scientific rigor.

A Field-Based Challenge

Our goal was to capture rapid, task-evoked neural markers of executive function immediately before and after a 50-km ultramarathon across multiple race events. This required a system that was fast to set up, comfortable for athletes already under physiological stress, robust to environmental noise, and transparent enough to support standard EEG analysis workflows.

At each race, athletes completed a brief visual oddball task, a well-established paradigm for eliciting event-related potentials (ERPs) linked to executive function (Sutton et al., 1965; Polich, 2007), while EEG was recorded. Testing took place in a quiet tent near the start and finish area, with pre-race assessments completed within hours of race start and post-race testing beginning within minutes of finishing. Setup time had to be minimal, instructions had to be clear and repeatable, and the entire testing protocol had to fit within a narrow post-race window while preserving data quality.

To meet these demands, we used a mobile EEG system designed to balance portability with research-grade signal access, namely Brain Products’ X.on mobile EEG device paired with the PEER acquisition app. The X.on’s fixed electrode montage and rapid fitting procedure allowed EEG recordings to begin within minutes, even in challenging outdoor conditions, while PEER enabled standardized task delivery and synchronized data acquisition across devices. Importantly, the system provided direct access to raw EEG signals rather than proprietary preprocessed metrics, a critical requirement for event-related potential research.

EEG signals were recorded during the oddball task using PEER and streamed into standard analysis environments, where data were processed using established ERP pipelines. Despite the inherent variability of a race environment, the recordings reliably captured canonical ERP components associated with executive function, including the N2 and P3 (Folstein & Van Petten, 2008; Polich, 2007). This demonstrates that mobile EEG can be used for time-locked, task-based cognitive neuroscience in real-world endurance settings.

Results

Ultramarathon racing produced consistent changes in both behavioral performance and neural indices of executive function. Behaviorally, athletes responded more quickly after the race but with reduced consistency. Reaction times were significantly shorter post-race and were accompanied by a substantial increase in trial-to-trial variability, while overall task accuracy remained high, indicating a shift in response regulation rather than a simple improvement or decline in performance.

At the neural level, EEG revealed clear alterations in event-related potentials associated with executive control. The amplitude of the N2 component, a marker of inhibitory control and conflict monitoring, was reduced following the race (Folstein & Van Petten, 2008). The P3 component showed a similar pattern, with reduced amplitude and shortened latency post-race, reflecting faster but less selective stimulus evaluation and attentional allocation (Polich, 2007).

The magnitude of ERP change varied across athletes. Reductions in N2 amplitude showed small associations with identified and introjected regulation on the Sport Motivation Scale, which index participation driven by internalized external goals and self-imposed pressure (Pelletier et al., 2013). Reductions in P3 amplitude showed a strong association with higher prerace DASS-21 total scores, which index symptoms of depression, anxiety, and stress measured one to two weeks before the race (Lovibond & Lovibond, 1995). Together, these findings suggest that psychological state assessed prior to competition may influence the degree of cognitive and neural change observed on race day. However, because psychological measures were not collected immediately before or after the race, it remains unclear how acute psychological states during competition interact with prolonged physiological strain to shape cognitive outcomes.

Expanding the Scope of Applied Neuroscience

This work illustrates how advances in mobile neurotechnology are expanding where and how cognitive neuroscience can be conducted. By moving EEG out of the lab and into real-world performance environments, researchers can begin to study cognition as it unfolds under genuine physiological and psychological stress.

For endurance sport scientists, this approach opens new opportunities to investigate how factors such as motivation, affective state, fueling strategies, and training history interact with brain function during prolonged competition. More broadly, it demonstrates that research-grade EEG can be successfully deployed in complex, less controlled settings.

As mobile EEG technology continues to evolve, its applications in sport, health, and performance science are likely to extend well beyond the laboratory, offering new insights into how the human brain adapts under extreme conditions.

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