Does intensity matter? A randomized crossover study of the role of acute exercise intensity on cognitive performance and motor speed and accuracy.

There is a well-recognized, yet nuanced, positive relationship between acute physical activity and cognitive function. However, the precise impact of exercise intensity remains ambiguous. We tested learning and memory, working memory and processing speed, and motor speed and accuracy across three distinct exercise intensities. A sample of 207 participants (100 female) between 18 and 44 years (mean age: 22.5±3.7years) completed all study procedures. Utilizing a within-subjects, cross-over design, participants completed moderate (35% VO₂ Max), vigorous (70% VO₂ Max), and sedentary (no exercise) conditions. Cognitive and motor assessments, including the Paced Auditory Serial Addition Test (PASAT), Rey Auditory Verbal Learning Test (RAVLT), Typing Speed Test, and Ten Key Data Entry Task, were conducted approximately 60min post-exercise. There were no significant differences in primary cognitive or motor outcome measures across the three exercise intensities, even with the study being strongly powered. There was, however, a small difference on the fastest trial of the PASAT, where vigorous-intensity exercise yielded slightly better performance compared to both sedentary and moderate-intensity exercise. This effect was no longer significant when including VO₂ Max or maximum heart rate as indicators of fitness. There were no interactions on outcome variables by exercise intensity when including biological sex in the models. Thus, a single bout of acute exercise, regardless of its intensity, did not alter cognitive and motor performance when measured approximately 1h post-exercise. Findings highlight the importance of large samples and suggest that the temporal dynamics post-exercise might play a pivotal role in cognitive outcomes.