No abstract

High-intensity interval exercise (HIIE) improves cerebral executive function (EF), but the improvement in EF is attenuated after repeated HIIE, perhaps because of lower lactate availability for the brain. This investigation examined whether improved EF after exercise relates to brain lactate uptake. Fourteen healthy, male subjects performed 2 HIIE protocols separated by 60 min of rest. Blood samples were obtained from the right internal jugular venous bulb and from the brachial artery to determine arterial-venous differences across the brain for lactate (a-v diff), glucose (a-v diff), oxygen (a-v diff), and brain-derived neurotrophic factor (BDNF; a-v diff). EF was evaluated by the color-word Stroop task. The first HIIE improved EF for 40 min, whereas the second HIIE improved EF only immediately after exercise. The a-v diff was unchanged, whereas the a-v diff increased similarly after both HIIEs, and the a-v diff increased, but the increase was attenuated after the second HIIE, compared with the first HIIE ( P < 0.05). The EF after HIIE correlated with the a-v diff ( r = 0.62; P < 0.01). We propose that attenuated improvement in EF after repeated HIIE relates to reduced cerebral lactate metabolism and is, thereby, linked to systemic metabolism as an example of the lactate shuttle mechanism.-Hashimoto, T., Tsukamoto, H., Takenaka, S., Olesen, N. D., Petersen, L. G., Sørensen, H., Nielsen, H. B., Secher, N. H., Ogoh, S. Maintained exercise-enhanced brain executive function related to cerebral lactate metabolism in men.

A single bout of aerobic exercise improves executive function (EF), but only for a short period. Compared with a single bout of aerobic exercise, we recently found that high-intensity interval exercise (HIIE) could maintain a longer improvement in EF. However, the mechanism underlying the effect of different exercise modes on the modifications of EF remains unclear. The purpose of the current investigation was to test our hypothesis that the amount of exercise-induced lactate production and its accumulation affects human brain function during and after exercise, thereby affecting post-exercise EF. Ten healthy male subjects performed cycle ergometer exercise. The HIIE protocol consisted of four 4-min bouts at 90% peak VO2 with a 3-min active recovery period at 60% peak VO2. The amount of lactate produced during exercise was manipulated by repeating the HIIE twice with a resting period of 60min between the 1st HIIE and 2nd HIIE. To evaluate EF, a color-word Stroop task was performed, and reverse-Stroop interference scores were obtained. EF immediately after the 1st HIIE was significantly improved compared to that before exercise, and the improved EF was sustained during 40min of the post-exercise recovery. However, for the 2nd HIIE, the improved EF was sustained for only 10min of the post-exercise recovery period, despite the performance of the same exercise. In addition, during and following HIIE, the glucose and lactate accumulation induced by the 2nd HIIE was significantly lower than that induced by the 1st HIIE. Furthermore, there was an inverse relationship between lactate and EF by plotting the changes in lactate levels against changes in EF from pre-exercise during the late phase of post-exercise recovery. These findings suggested the possibility that repeated bouts of HIIE, which decreases lactate accumulation, may dampen the positive effect of exercise on EF during the post-exercise recovery.