All studies were performed by a single registered diagnostic cardiac sonographer in participants who held vasoactive medications and were instructed not to smoke cigarettes or exercise prior to testing.1 (link),2 (link) After a 15-minute supine rest, left arm brachial blood pressure was measured by oscillometric sphygmomanometry (OMRON Model HEM-907XL; Omron Healthcare Inc., Kyoto, Japan). The right BA was imaged using a linear array vascular ultrasound transducer (ACUSON Sequoia Model C512, 8L5c transducer; Siemens Medical Solutions, Malvern, PA, USA). Extra-vascular landmarks were labeled to ensure consistent imaging within and between studies over time. Overall gain, time-gain compensation settings, and contrast were the same across studies for each participant. After baseline B-mode and Doppler images were obtained, a blood pressure cuff was placed proximal to the visualized BA segment, was inflated for 4 minutes at 50 mmHg above systolic pressure, and adjusted upwards if necessary to ensure complete occlusion using a Hokanson E20 Rapid Cuff Inflation System (D.E. Hokanson Inc., Bellevue, WA, USA). After cuff release, longitudinal images of the BA and Doppler blood flow were obtained up to 90 seconds after cuff deflation.