Does acute dynamic exercise improve brain cognitive function in humans?

To test the hypotheses that 1) acute dynamic exercise can improve cognitive function and 2) changes in cerebral blood flow of the frontal brain may be associated with improved cognitive function, a Stroop color‐word test (SCWT) was performed in 12 subjects before and 5 min after cycling exercise for 15 min at 20%, 40%, and 60% of maximum voluntary exercise. SCWT can evaluate quantitatively cognitive function. When a “color word” was displayed in a color different from “the color's meaning”, the subjects were asked to quickly answer the color of the word. The total time and the number of errors in 100 SCWT trials were recorded as index of cognitive function. We measured the concentration of oxy‐hemoglobin (O 2 Hb) in the frontal brain with a near‐infrared spectroscopy to monitor local cerebral blood flow. The total time for SCWT was shortened and O 2 Hb was increased only by 40%‐ and 60%‐exercise. The increase in O 2 Hb started 5 min after the onset of the exercise. The number of error was not altered by any intensity of exercise. When the duration of 40%‐exercise was shortened to 5 min in 6 subjects, both the total time for SCWT and O 2 Hb were not altered. These results suggest that 1) acute dynamic exercise at a moderate intensity for 15 min, but not 5 min, is able to improve brain cognitive function and 2) the improved cognitive function may be in association with increased cerebral blood flow of the frontal brain.