Evidence for temperature-mediated regional increases in cerebral blood flow during exercise

Acute moderate‐intensity exercise increases core temperature (Tc; +0.7‐0.8°C); however, such exercise increases cerebral blood flow (CBF; +10‐20%) mediated via small elevations in arterial urn:x-wiley:00223751:media:tjp13960:tjp13960-math-0003 and metabolism. The present study aimed to isolate the role of Tc from urn:x-wiley:00223751:media:tjp13960:tjp13960-math-0004 on CBF regulation during submaximal exercise. Healthy adults (n = 11; 10 males/one female; 26 ± 4 years) participated in two interventions each separated by ≥48 h: (i) 60 min of semi‐recumbent cycling (EX; 50% workload max) and (ii) 75 min of passive heat stress (HS; 49°C water‐perfused suit) to match the exercise‐induced increases in Tc (EX: Δ0.75 ± 0.33°C vs. HS: Δ0.77 ± 0.33°C, P = 0.855). Blood flow (Q) in the internal and external carotid arteries (ICA and ECA, respectively) and vertebral artery (VA) (Duplex ultrasound) was measured. End‐tidal urn:x-wiley:00223751:media:tjp13960:tjp13960-math-0005 and urn:x-wiley:00223751:media:tjp13960:tjp13960-math-0006 were effectively clamped to resting values within each condition. The QICA was unchanged with EX and HS interventions (P = 0.665), consistent with the unchanged end‐tidal urn:x-wiley:00223751:media:tjp13960:tjp13960-math-0007 (P = 0.327); whereas, QVA was higher throughout both EX and HS (EX: Δ16 ± 21% vs. HS: Δ16 ± 23%, time effect: P = 0.006) with no between condition differences (P = 0.785). These increases in QVA contributed to higher global CBF throughout both EX and HS (EX: Δ12 ± 20% vs. HS: Δ14 ± 14%, time effect: P = 0.029; condition effect: P = 0.869). The QECA increased throughout both EX and HS (EX: Δ42 ± 58% vs. HS: Δ53 ± 28%, time effect: P < 0.001; condition effect: P = 0.628). Including blood pressure as a covariate did not alter these CBF findings (all P > 0.05). Overall, these data provide new evidence for temperature‐mediated elevations in posterior CBF during exercise that are independent of changes in urn:x-wiley:00223751:media:tjp13960:tjp13960-math-0008 and blood pressure.