Relationship between cognitive function and parasympathetic nerve activity after acute mild to moderate intensity exercise

After exercise training, improvement in cognitive function is associated with high parasympathetic nervous activity. However, the relationship between cardiac autonomic nervous activity and cognitive function after acute exercise may differ from that after chronic exercise, because parasympathetic nervous activity decreases with acute exercise. Here, we examined the relationship between parasympathetic nervous activity and cognitive function after acute exercise. Twelve male participants performed cognitive tasks in exercise and non-exercise conditions, with a randomized crossover design. Participants in the exercise condition ran on a treadmill for 10 min, with a running speed corresponding to a rate of perceived exertion (RPE) of 10–12 in each subject. Cognitive tasks were performed before and after both conditions. Heart rate variability during cognitive tasks was measured to evaluate autonomic nervous system activity. In the exercise condition, RPE was 11.1 ± 0.2 (mean ± SE) immediately after exercise. Exercise at RPE 10–12 improved reaction times in Go trials (from 687.8 ± 55.2 to 568.2 ± 45.9 ms, P < 0.05). In the non-exercise condition, cognitive performance remained stable throughout the experiment. In addition, parasympathetic nervous activity (high-frequency component of heart rate variability) remained low after exercise compared with before exercise (from 586.4 ± 122.5 to 372.8 ± 92.9 ms2, P < 0.05). In contrast, parasympathetic nervous activity increased in the non-exercise condition (from 516.6 ± 94.9 ms2 to 642.5 ± 85.6 ms2, P < 0.05). The present results suggest that improvement in cognitive function after acute exercise may be related to reduced parasympathetic nervous activity.