2.4. Measurement of Flow-Mediated Dilation

Brachial artery FMD was measured according to the previous studies [28]. In short, high-resolution ultrasonography was used with a 5–12 MHz linear transducer on an HDI 5000 system (Washington, USA). The participants were supine for at least 15 min, and then their brachial arteries were scanned longitudinally 2 to 10 cm proximal to the antecubital fossa. After increasing the pressure in an upper-forearm sphygmomanometer cuff to 250 mmHg for 5 min and monitoring electrocardiogram after cuff deflation for 90 s, FMD was taken as the percentage augment in mean diastolic diameter after reactive hyperemia 55 to 65 s following deflation to baseline.