Effects of exercise intensity and neuromodulation on inhibitory control, cerebral oxygenation and cardiac autonomic regulation: randomized intervention study

There is a growing interest in the effects of non-pharmacological interventions on cognitive functions. Exercise and transcranial direct current stimulation (TDCS) have been shown to influence brain function in improving inhibitory control, promoting an increase in blood flow and cerebral oxygenation. The purpose of the present study was to analyze the effects of exercise intensity and transcranial direct current stimulation associated with acute physical exercise on inhibitory control, cerebral oxygenation and cardiac autonomic regulation in adults. Twenty physically active adult males were recruited for convenience. To verify the inhibitory control was used the color test of Stroop. The volunteers performed, on different days and random order, four encounters, being: three rectangular exercises for 30 minutes, in a mild, moderate or vigorous intensity and a control condition. After that moment, we had two more meetings, with the participation of all the volunteers submitted to the TDCS real session and Sham in a randomized and counterbalanced way every other day. The TDCS was applied for 20 minutes with current intensity of 2 mA, the cathode electrode was positioned in the T4 region, and the anode in the F3 region on Pre Frontal Cortex (PFC). Brain activity was assessed from the monitoring of cerebral hemodynamics through absolute concentrations of oxyhemoglobin (HbO), deoxyhemoglobin (Hb), total hemoglobin (Hbtot), using near infrared spectroscopy (NIRS). The two-way ANOVA (2 conditions X 3 moments) with repeated measurements was used to compare the responses of inhibitory control, brain activity and HRV between conditions. The significance of the analyzes was assumed when P <0.05. Comparing the intensities of the exercise vs control, the moderate and vigorous intensities presented a greater oxygenation indicating an increase of the activity in the prefrontal cortex, concomitantly with the improvement in the inhibitory control. Exerciseassociated TDCS increased brain activity through increased post-exercise oxygenation. However, these brain changes did not influence better inhibitory control. On the other hand, physical exercise increased inhibitory control, decreasing reaction time and errors when compared to the control condition. In addition, the exercise-related TDCS did not modulate the Heart Rate Variability (HRV). These results suggest that non-pharmacological practices of low cost, easy applicability and non-invasiveness can be a useful tool in public health for prevention and improvement of cognitive behavior.