“To measure is to know”: no relationship between cerebrovascular and peripheral shear‐mediated dilation in young adults

Experimental Physiology

Bailey

et al. 2021

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Cerebrovascular reactivity (CVR) of middle cerebral artery velocity (MCAv) to CO 2 is a common method to assess cerebrovascular function. Yet, the approaches used to calculate CVR outcomes vary. The aim of this study was to explore the withinand between-day reliability of traditional CVR outcomes. The second aim was to explore the reliability of novel kinetic-based analyses. Healthy adults (n = 10, 22.3 ± 3.4 years) completed assessments of CVR over 4 min using a fixed fraction of inspired CO 2 (6%). This was repeated across four separate visits (between-day), and on one visit measures were repeated 2.5 h later (within-day). No mean biases were present between assessments for traditional CVR metrics, expressed as absolute (cm/s/mmHg) or relative (%/mmHg) outcomes (minute 3, minute 4, peak 1 s, peak 30 s) (betweenday: P > 0.14, η p 2 < 0.20; within-day: P > 0.22, d > 0.27). Absolute, rather than relative, CVR yielded the most reproducible parameters (coefficient of variation: 8.1-13.2%vs. 14-83%, respectively). There were significant differences between CVR outcomes (P < 0.001, η p 2 > 0.89) dependent on the time point used to determine CVR, as a steady state MCAv response was rarely observed. Furthermore, the MCAv response was not reproducible within an individual (κ = 0.15, P = 0.09). No mean differences were present for novel kinetic outcomes (amplitude, time-delay, time constant) (between-day: P > 0.05, d < 0.33; within-day: P > 0.38, d < 0.25). The results support the need for standardisation and indicate CVR should be defined as a dynamic peak, rather than a set time point for increased reliability. For novel kinetic outcomes variability was greater (CV: 8.7-120.9%) due to the nature of time-based metrics.

Section: Novel Kinetic Analysesmentioning

confidence: 52%

Section: Novel Kinetic Analysesmentioning

confidence: 99%

The within‐ and between‐day reliability of cerebrovascular reactivity using traditional and novel analytical approaches

Experimental Physiology

Bailey

et al. 2021

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The acute and postprandial effects of sugar moiety on vascular and metabolic health outcomes in adolescents

Appl. Physiol. Nutr. Metab.

Banks

et al. 2021

This study explored the cardiometabolic responses to sugar moieties acutely, and following a subsequent mixed meal tolerance test (MMTT). Twenty-one healthy adolescents (N=10 female, 14.3±0.4 years) completed three experimental and one control condition, in a counterbalanced order. These consisted of different drinks to compare the effect of 300 mL of water (control), or 300 mL of water mixed with 60 g of glucose, fructose or sucrose, on vascular function (flow-mediated dilation; FMD, microvascular reactivity (total hyperaemic response; TRH); and cerebrovascular reactivity; CVR), and blood samples for [uric acid], [glucose], [triglycerides] and [lactate]. FMD increased 1 hour after glucose and sucrose (P<0.001, ES≥0.92) but was unchanged following fructose and water (P>0.19, ES>0.09). CVR and TRH were unchanged 1 hour following all conditions (P>0.57, ES>0.02). Following the MMTT, FMD was impaired in all conditions (P<0.001, ES>0.40) with no differences between conditions (P>0.13, ES<0.39). Microvascular TRH was increased in all conditions (P=0.001, ES=0.88), and CVR was preserved in all conditions post MMTT (P=0.87, ES=0.02). Blood [uric acid] was elevated following fructose consumption and the MMTT (P<0.01, ES>0.40). Consumption of a sugar sweetened beverage did not result in vascular dysfunction in healthy adolescents, however the vascular and metabolic responses were dependent on sugar moiety. Highlights: • Glucose consumption acutely increases peripheral vascular function in healthy adolescents. • Acute sugar sweetened beverage consumption (sucrose) does not result in adverse vascular outcomes. • Elevations in uric acid are observed with fructose consumption, which may have implications over repeated exposure.

The acute effect of exercise intensity on peripheral and cerebral vascular function in healthy adults

Lester

Journal of Applied Physiology

et al. 2022

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.