Utilizing nasal breathing during aerobic exercise is associated with a higher cerebral blood flow volume

Nasal-only breathing (NB) during exercise can induce a transient hypercapnic state that increases cerebral blood flow (CBF). However, whether using NB as a training modality over several weeks yields favorable cerebrovascular adaptations remains unknown. This study investigated whether a four-week aerobic training program using NB results in superior cerebral volumetric blood flow (VBF) during a graded exercise test (GXT) compared to training with unrestricted combined breathing (CB). Twenty-two healthy males were randomized to an NB or CB group. Both groups performed pre- (V1) and post-intervention (V2) GXTs. The exercise training intervention consisted of four non-consecutive days/week of supervised, moderate-intensity aerobic exercise for four weeks. VBF in the internal (ICA) and external (ECA) carotid arteries was assessed via doppler ultrasound, and respiratory gases were measured with a metabolic cart. Following the intervention (V2), the NB group (14.68 ± 0.78 cm 3 /s) exhibited significantly ( p < 0.05) greater ICA VBF during the peak systolic phase at 100% of V̇O 2max compared to the CB group (10.80 ± 0.78 cm 3 /s). An exploratory descriptive responder analysis showed that 63% of the NB group increased their peak systolic VBF from V1 to V2 versus 31% of the CB group. Mechanistically, at V2, the NB group demonstrated a robust cardiorespiratory change, characterized by a normalized oxygen pulse during the GXT. Overall, four weeks of aerobic training with NB is associated with a greater cerebral VBF during aerobic exercise. This adaptation coexisted with an improved cardiovascular efficiency that must be explored further to determine acute versus chronic NB-mediated responses/adaptations. This study was registered with ISRCT(The UK’s Clinical Study Registry), registration number ISRCTN11953452.