Due to methodological and technical challenges brain cortical activity has rarely been investigated during endurance exercise. In this respect, it is not surprising that effects of an acute bout of interval training on central nervous activity have not been examined yet. Therefore, the aim of the present investigation was to characterize acute adaptations of brain cortical activity and established parameters to a high intensity endurance session. In a laboratory study sixteen endurance-trained cyclists completed an exercise bout including 3 interval series on a high-performance bicycle ergometer. Changes in cortical activity were recorded with quantitative electroencephalography (EEG) and analyzed in five specific frequency ranges (theta, alpha-1, alpha-2, beta-1, beta-2).