Effects of interval versus continuous exercise on cerebral vascular flow-mediated dilatation in young healthy males.

Aerobic exercise reduces the risk of cerebrovascular dysfunction. One proposed mechanism is exercise-induced increases in cerebral shear stress (SS) improving cerebral endothelial function. A recent report indicated that interval exercise (Int-Ex) induces greater cerebral SS than continuous exercise (Con-Ex); however, its effect on cerebral endothelial function remains unclear. We hypothesized that Int-Ex would enhance cerebral SS and, consequently, cerebral endothelial function more than Con-Ex. Fourteen healthy males (21 ± 0.6 years) completed 32 min of Int-Ex and work-equivalent Con-Ex on a semi-recumbent bike on separate days. Cerebrovascular flow-mediated dilatation (cFMD) was assessed before exercise (Pre), 15 min (Post-15) and 40 min post-exercise (Post-40). cFMD was defined as peak internal carotid artery vasodilatation (Δ% from baseline; Duplex ultrasound) in response to a 30-s hypercapnic exposure, raising end-tidal partial pressure of carbon dioxide by ~7 mmHg. Post-exercise cerebral SS was greater after Int-Ex versus Con-Ex (p = 0.002). Int-Ex evoked a ~37% increase in post-exercise cerebral SS compared to rest, with a negligible increase for Con-Ex. cFMD did not differ between Int-Ex and Con-Ex trials before exercise (Pre, 6.35 ± 3.89% vs. 5.54 ± 3.83%; p = 0.542) and remained unchanged post-exercise (Post-15, 7.20 ± 4.47% vs. 6.13 ± 4.08%; Post-40, 5.69 ± 3.86% vs. 6.94 ± 3.55%; p = 0.583). These results indicate that Int-Ex and Con-Ex have similar acute effects on cerebral endothelial function.