RESUMO
Transcranial direct current stimulation (tDCS) is acknowledged to modulate autonomic cardiac activity and hemodynamic responses at rest and during exercise. However, its potential to optimize postexercise hypotension (PEH) has not been investigated. This study investigated the effects of anodal tDCS applied over the medial prefrontal cortex (mPFC) upon blood pressure (BP) and heart rate variability (HRV) throughout 60 min following acute aerobic exercise. Fifteen young men (27.5 ± 5.2 yrs; 72.9 ± 8 kg; 170 ± 0.1 cm; 124.1 ± 1.9/67.7 ± 2.1 mmHg) underwent three counterbalanced experimental sessions: a) anodal tDCS + exercise (tDCS); b) sham stimulation + exercise (SHAM); c) non-exercise control (CONT). Exercise consisted in 50-min cycling at 65-70% heart rate reserve. BP and HRV were assessed during 60-min postexercise. Mean reduction in systolic BP occurred after tDCS vs. SHAM (-4.1 mmHg; P=0.03) and CONT (-5.8 mmHg; P=0.003), and in MAP vs. CONT (-3.0 mmHg, P=0.03). Parasympathetic activity lowered after tDCS and SHAM vs. CONT, as respectively reflected by R-R intervals (-328.1% and -396.4%; P = 0.001), SDNN (-155.7% and -193.4%; P = 0.006), and pNN50 (-272.3% and -259.1%; P = 0.021). There was a clear tendency of increased sympatho-vagal balance vs. CONT (P = 0.387) after SHAM (+246.3%), but not tDCS (+25.9%). In conclusion, an aerobic exercise bout preceded by tDCS applied over mPFC induced PEH in normotensive men. Parasympathetic activity lowered, while sympatho-vagal balance increased after both tDCS and SHAM vs. CONT. However, these responses seemed to be tempered by anodal stimulation, which might help explaining the occurrence of PEH after tDCS and not SHAM. These findings warrant further research on the role of tDCS within exercise programs aiming at BP management.