Author(s): EVELIS, K., PLAKANE, L., KOLESOVS, A., Institution: UNIVERSITY OF LATVIA, Country: LATVIA, Abstract-ID: 2486

Introduction
Exercise has been shown to influence brain health and performance through multiple mechanisms. Previous research suggests that exercise may promote neuroplasticity, potentially mediated by increases in brain-derived neurotrophic factor (BDNF) [1]. Beyond neurobiological measures, emotional states and cognitive functioning can also be assessed. Therefore, the objective of the current study was to investigate how acute exercise impacts core affect, lactate concentration and cognitive processes.
Methods
Sixty participants (aged 19-31) were randomly assigned (using block randomization) to one of three groups: reduced-exertion high-intensity training (REHIT) group - 15 second maximum effort sprints, followed by 200s rest, 10 second light cycling was performed before the next sprint, 4 cycles in total, high-intensity interval training (HIIT) group - 90s high-intensity intervals followed by 90s rest, 5 cycles in total, or control group - watched 15-minute education video. The exercise protocols were completed on a Cycle Ergometer. Core affect was assessed using the Swedish Core Affect Scale. Cognitive performance was evaluated using measures of reaction time, working memory, inhibitory control and motor skills. Capillary blood lactate concentration was also measured. The measurements were done pre- and post- intervention (exercise or control).
Results
Lactate increased in both exercise groups (p < 0.001), with significantly larger increases in the REHIT group, compared to HIIT (p < .001).
Regarding core affect, both HIIT and REHIT significantly increased activation (p < .001 and p = .019, respectively). However, only the HIIT group demonstrated significant increases in pleasant activation (p = .019) and calmness, reflected by reductions in unpleasant activation (p = .019).
In the cognitive tests, the control group exhibited slower simple reaction time in the post-measurement (p < .001), whereas neither exercise group showed pre- to post-test changes. No statistically significant effects were found for working memory, inhibitory control, motor skills or complex reaction time.
Discussion
A single 15-minute bout of exercise significantly increased lactate concentration in both HIIT and REHIT conditions, with REHIT producing the largest elevations. Both exercise protocols also increased subjective activation (energy levels), while HIIT additionally enhanced calmness and interest. The slowing of reaction time in the control group suggests a fatigue or vigilance-decline effect that was not observed in the exercise groups, indicating that acute exercise may help maintain alertness. However, no changes were detected in other cognitive domains, implying that the relationship between exercise-induced lactate increases, cognition and affective states is complex and warrants further investigation.
References
1. Evelis, K., Kolesovs, A., Rostoka, E., Plakane L. Sci Rep 15, 38322 (2025).