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Feel the burn to improve cognition

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Science Translational Medicine  29 Nov 2017:
Vol. 9, Issue 418, eaar2444
DOI: 10.1126/scitranslmed.aar2444

Abstract

Increased brain lactate uptake is related to improved executive function following high-intensity interval exercise.

There is emerging evidence that exercise improves cognition; however, the mechanisms underlying the beneficial effects are unclear. High-intensity interval exercise is a modality that is gaining momentum due to its effects on outcomes such as body composition and fitness. The key to high-intensity interval exercise is the exertion of near-maximal effort for repeated short bursts interspaced with short durations of lower effort. The energy distribution during training has profound effects on cellular respiration; therefore, affecting the type of fuel that is available to the muscles and the brain. Previous studies showed that high-intensity interval exercise increases circulating lactate, a preferred fuel for neurons. Despite this, there is relatively sparse evidence investigating the effect of high-intensity interval training on cognition.

A new study by Hashimoto et al. investigates the effects of high-intensity interval exercise on brain lactate uptake and executive function during and immediately after each of two consecutive bouts of high-intensity interval exercise. Investigators measured the difference between arterial and internal jugular venous lactate in addition to glucose and several neurohumoral outcomes, to characterize their uptake into the brain. During the first bout of high-intensity interval exercise, they found a significant increase in brain lactate uptake and improvement in executive function, whereas glucose or other neurohumoral measures were not modulated. After the first bout, the effects on lactate uptake and on cognitive function were also maintained during the period of recovery. In comparison, the second bout of high-intensity interval exercise induced a smaller boost in lactate uptake, and the duration of executive function improvement was attenuated. The investigators suggest that the increase in cerebral metabolism during exercise to maintain neuronal activation may be related to increased brain lactate uptake, and that relative depletion of muscle glycogen prior to the second bout may have attenuated the increase in lactate available for use during the second bout of exercise.

This study indicates that lactate is used by the brain during exercise, and that lactate uptake occurs in relationship to its arterial concentration. The findings also suggest that brain lactate might be involved in the modulation of executive function induced by exercise. This study does have limitations, including the experimental group that consisted of young, healthy male subjects. However, the results are in agreement with clinical studies in older cohorts that show executive function is improved following exercise in humans. These findings provide a new direction for research into the mechanism underlying the relationship between exercise and cognition, and warrant further investigation to determine if repeated acute exercise–induced changes in lactate produce long-term cognitive benefit.

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