Introduction: There are studies indicating the positive effects of aerobic exercise on increasing oxygenation to the brain. However, it still remains unclear what optimal exercise intensity induces high cerebral oxygenation in the prefrontal cortex (PFC) of the brain. [Purpose] The purpose of this study was to investigate the effect of exercise intensity on oxygenated haemoglobin (oxyHb) concentration changes in the PFC of humans.

Methods: 

After 30 min of rest, 17 young subjects performed cycling exercise on the ergometer with progressively increases of intensities for every 5 min until volitional exhaustion. OxyHb concentration changes in the PFC and respiratory responses were measured using the near infrared spectroscopy (NIRS) and a metabolic cart, respectively. Blood lactate and glucose were measured using finger prick blood samples. Results and discussion: Oxygen consumption (VO₂) showed a constant increase with increasing exercise intensity. On the other hands, oxyHb changes in the PFC decreased at higher exercise intensities. This suggests that VO2 and cerebral oxyHb in the PFC are not related.