Pulse wave velocity (PWV) deceleration to reactive hyperemia–flow-mediated slowing (FMS)–has been suggested as an alternative method to flow-mediated dilation (FMD) to evaluate brachial artery endothelial function. FMS is suggested to address major caveats of the FMD procedure including its suboptimal repeatability and high-operator dependency. However, the repeatability of FMS has not been thoroughly examined, especially given the plethora of methods claiming to measure PWV. We assessed and compared the intra- and inter-day repeatability of FMS as measured by piezoelectric pressure mechanotransducers placed in the carotid and radial arteries, and brachial artery FMD as measured by echo-tracking. Twenty-four healthy male participants aged 23–75 yr, were examined on three separate days to assess intra and inter-day repeatability. All FMD and FMS examinations were conducted simultaneously by the same researcher complying with standardized guidelines. Repeatability was examined with intraclass correlation coefficient (ICC; >0.80), coefficient of variation (CV; <15%), and limits of agreement (95% LOA). Relative (%) FMD and FMS were scaled for baseline brachial artery diameter and PWV, respectively. Intra- (ICC: 0.72; CV: 136%; 95% LOA: -19.38 to 29.19%) and Inter-day (ICC: 0.69; CV: 145%, 95% LOA: -49.50 to 46.08%) repeatability of %FMS was poor, whereas %FMD demonstrated moderate-to-good intra- (ICC: 0.93; CV: 18%, 95% LOA: -3.02 to 3.75%) and inter-day repeatability (ICC: 0.74; CV: 25%, 95% LOA: -9.16 to 7.04%). Scaling FMD reduced the intra-day CV (-5%), and the uncertainty of the 95% LOA (- 37.64 to 35.69%) estimates of FMS. Carotid-radial artery FMS showed poorer repeatability compared to FMD.

We compared response patterns of cardiovagal modulation through indices of heart-rate variability (HRV) and baroreflex sensitivity (BRS) at 10 and 60 min following an acute bout of high-intensity interval exercise (HIIE) and moderate-intensity continuous exercise (MICE) in active young and older adults. Twelve young (aged 20-40 years) and older (aged 57-76 years) healthy and active male adults performed an isocaloric acute bout of HIIE, MICE, or a non-exercise condition in a randomized order. HRV and BRS indices were analysed offline with R-R intervals obtained from a supine position. HIIE decreased natural logarithm (Ln) standard deviation of NN intervals (d= -0.53; 95% CI: -0.77 to -0.30 ms, p<0.001), Ln-root mean square of successive differences (d= -0.85; 95% CI: -1.09 to -0.61 ms, p<0.001), Ln-high-frequency power (d= -1.60; 95% CI: -2.11 to -1.10 ms2; p<0.001), and BRS (d= -6.28; 95% CI: -8.91 to -3.64 ms/mmHg, p <0.001) following exercise in young and older adults, whereas MICE did not. Indices returned to baseline following 60 min. We found no evidence of age-associated response patterns in HRV or BRS to a single bout of HIIE or MICE in active participants. HIIE reduced cardiovagal modulation in active young and older adults, returning to baseline values 60 min into recovery.

Brachial vascular function after acute aerobic exercise in older adults with and without type 2 diabetes Purpose: The acute exercise model provides clinical insights regarding vascular dysfunction in adults with type 2 Diabetes Mellitus (T2DM), as it uncovers abnormalities not normally present at rest. However, whether vascular responses to acute exercise in adults with T2DM are intensity-dependent, and whether response patterns differ with aging and disease, remains unknown. Thus, we examined brachial artery flow-mediated dilation (FMD) and flow-mediated slowing (FMS) of pulse wave velocity (PWV), 10 and 60-min after an acute bout of high-intensity interval exercise (HIIE) and moderate-intensity continuous exercise (MICE) in middle-aged and older men with and without T2DM compared to young men without T2DM. Hypothesis: HIIE would induce a larger decrease in FMD immediately after exercise cessation compared to MICE in older men with and without T2DM. Methods: Twelve males with (57-84 yr) and without (57-76 yr) T2DM, and 12 healthy young adults (20-40 yr), completed an isocaloric acute exercise bout of HIIE, MICE, and a non-exercise condition in randomized order. FMD and FMS were evaluated and offline analyzed by the same researcher following standard guidelines. Central and peripheral arterial stiffness were measured via applanation tonometry estimates of carotid-femoral PWV (cfPWV) and carotid dorsalis pedis PWV (cdPWV), respectively. Statistical inferences were performed using linear mixed models. Results: %FMD was reduced (d= - 5.94, 95% CI: -10.50 to -1.38 %, p=0.002), whereas %FMS was increased (d= 4.55, 95% CI: 0.62 to 8.48%, p=0.01), 10-min after HIIE only in older adults with T2DM, returning to resting values 60-min into recovery. Conversely, %FMD was increased (d= 5.33, 95% CI: 0.76 to 9.89%, p=0.009) 10-min after MICE only in older adults with T2DM, while cfPWV and cdPWV remained unchanged following HIIE and MICE in all groups. There were no group differences at rest in brachial %FMD and %FMS, while cfPWV and cdPWV were higher in older adults with T2DM compared to age-matched controls (cfPWV: d= 1.94, 95% CI: 0.44 to 3.44 m. s-1, p=0.009). Conclusions: We found evidence of intensity- and disease-dependent vascular responses to acute aerobic exercise. These findings suggest that high-intensity acute exercise transiently impairs vascular function in older adults with T2DM, which may constitute an important trigger for exercise-based long-term improvements in vascular function. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Flow-mediated slowing (FMS) is a non-invasive measure of endothelial function measured through reactive hyperemia-induced changes in pulse wave velocity (PWV). FMS is suggested to mitigate known pitfalls of flow-mediated dilation (FMD) including suboptimal repeatability and high-operator dependency. However, the few single-rater studies that examined FMS repeatability have shown controversial results and used only regional measurements of PWV, which might not reflect local brachial artery stiffness responses to reactive hyperemia. We assessed the inter- and intra-rater repeatability of ultrasound-based changes in local PWV (FMS) and diameter (FMD). Twenty-four healthy male participants aged 23–75 yr, were examined on two separate days. Reactive hyperemia-induced changes in PWV were calculated using a tailored R-script. The inter- and intra-rater repeatability were tested with the intraclass correlation coefficient (ICC), coefficient of variation (CV), and the Bland-Altman plot estimates. The inter-rater repeatability of FMS (bias: -0.08%; ICC: 0.85; 95% CI: 0.65 to 0.93; CV: 11%) and FMD (bias: -0.02%; ICC: 0.98; 95% CI: 0.97 to 0.99; CV: 7%) showed overall good repeatability over different days. The intra-rater repeatability of FMD (1st rater: bias: 0.27%; ICC: 0.90; 95% CI: 0.78 to 0.96; CV: 14%; 2nd rater: bias: 0.60%; ICC: 0.85; 95% CI: 0.64 to 0.94; CV: 18%) was better than FMS (1st rater: bias: -1.03%; ICC: 0.76; 95% CI: 0.44 to 0.91; CV: 21%; 2nd rater: bias:-0.49%; ICC: 0.70; 95% CI: 0.34 to 0.80; CV: 23%) but not different between raters. Ultrasound-based local measurements of PWV deceleration reactive hyperemia were repeatable among the raters.