Preserved brain function and reversible cognitive adaptation during endurance exercise

Endurance exercise imposes extreme metabolic demands on the adult human brain, raising the question of how core brain function is preserved under physiological challenge. We previously showed that marathon running induces reversible reductions in myelin within specific white-matter tracts, suggesting adaptive structural change under metabolic stress. Here, we asked whether this process is functionally tolerated. Neurophysiological recordings revealed maintained conduction latencies across motor, somatosensory, visual, and auditory pathways within 48 hours after race completion, indicating intact axonal signal transmission despite reduced myelin content. Cognitive testing revealed selective and transient modulation of higher-order processing, including attenuated practice-related gains in processing speed and short-lived increases in interference, whereas visuomotor speed and executive flexibility were preserved. All cognitive measures normalized one month after the race, supporting an adaptive framework linking myelin change with preserved brain function under extreme metabolic stress.