LAUSR

The acute effect of exercise intensity on cerebrovascular reactivity, and whether this mirrors changes in peripheral vascular function, has not been investigated. The aim of this study was to explore the acute effect of exercise intensity on cerebrovascular reactivity (CVR) and peripheral vascular function in healthy young adults (n=10, 6 females, 22.7 ± 3.5 years). Participants completed four experimental conditions on separate days: high intensity interval exercise (HIIE) with intervals performed at 75% maximal oxygen uptake (V̇O2max; HIIE1), HIIE with intervals performed at 90% V̇O2max (HIIE2), continuous moderate intensity exercise (MIE) at 60% V̇O2max and a sedentary control condition (CON). All exercise conditions were completed on a cycle ergometer and matched for time (30 min) and average intensity (60% V̇O2max). Brachial artery flow-mediated dilation (FMD) and CVR of middle cerebral artery blood velocity were measured before exercise, and one- and three hours post-exercise. CVR was assessed using transcranial Doppler ultrasonography to both hypercapnia (6% carbon dioxide breathing) and hypocapnia (hyperventilation). FMD was significantly elevated above baseline one and three hours following both HIIE conditions (P<0.05), but FMD was unchanged following the MIE and CON trials (P>0.33). CVR to both hypercapnia and hypocapnia, and when expressed across the end-tidal CO2 range, was unchanged in all conditions, at all time points (all P>0.14). In conclusion, these novel findings show that the acute increases in peripheral vascular function following HIIE, compared to MIE, were not mirrored by changes in cerebrovascular reactivity, which was unaltered following all exercise conditions in healthy young adults.