Effect of Different Exercise Modes on Cerebrovascular Shear in Humans

PURPOSE: To what extent exercise impacts the cerebrovasculature is dependent on exercise mode. This difference may be attributable to shear stress in the cerebral vasculature that effects improvements in vascular endothelial function. For the first time, we determined if an acute bout of isovolume interval exercise compounds cerebrovascular shear rate. METHODS: Eleven young men were randomly assigned to perform continuous exercise (Continuous Ex) or interval exercise (Interval Ex) of semi-recumbent cycling. During the Continuous Ex, subjects performed continuous cycling at 80W for 12 mins. During the Interval Ex, subjects performed 3 bouts of interval cycling (2 mins at 60W and 2 mins at 100W) that was volume matched with Continuous Ex. Shear rate in the internal carotid artery (ICA) was determined using Doppler ultrasound. RESULTS: Time averaged ICA shear rate was higher during Int Ex compared to Continuous Ex (351±75 vs. 330±61 /s, P=0.038) and the elevation was maintained throughout recovery (327±86 vs. 290±56 /s, P=0.014). CONCLUSION: These data are the first to highlight that a single acute bout of interval exercise compounds cerebrovascular shear, providing a mechanistic basis underlying its superior neuroprotective benefits.