LAUSR

Flow-mediated dilation (FMD) is a noninvasive measure of endothelial function and is a predictor of future cardiovascular disease risk. Previous studies have shown that biological sex modulates the FMD response to acute submaximal exercise in healthy older adults. However, the FMD response to maximal exercise has not been investigated in older adults; thus, whether sex impacts this response remains unknown. Therefore, the purpose of this study was twofold: 1) to investigate the FMD response to maximal exercise in older adults and 2) to test the hypothesis that FMD following maximal exercise will change differently in healthy older men compared with women. We studied twenty sedentary adults (50% women, age: 66±1 vs. 66±1 yrs, men vs. women, mean±SE, P>0.9), free of major clinical disease, who were not on hormone replacement therapy. Women were all postmenopausal. Vascular function was assessed before and after maximal exercise, based on a modified Balke treadmill test. FMD was assessed in response to 5 min forearm occlusion at 250 mmHg using brachial artery ultrasonography. We found pre-occlusion brachial diameter was larger in older men compared with women before (5.04±0.18 vs. 4.27±0.09 mm, P=0.002) and after maximal exercise (4.75±0.16 vs. 3.98±0.12 mm, P=0.001), but there was no sex × time interaction (P=0.1). Peak shear rate was significantly lower in older men compared with women before exercise (1852±81 vs. 2265±129 sec-1, P=0.01) and did not change after maximal exercise in either group (P=0.2). FMD was not significantly different in older men compared with women (P=0.1) before exercise and significantly increased following maximal exercise in both older men (3.84±0.66 vs. 6.55±1.27 %, pre- vs. post-exercise, P=0.009) and women (2.32±0.61 vs. 5.65±1.07 %, P=0.002), but the response was not impacted by sex (P=0.6 for sex × time interaction). When FMD was allometrically scaled to assess the potential effect of pre-occlusion diameter, our findings remained unchanged. Time to peak dilation was delayed in older men and women similarly following maximal exercise (51±2 vs. 75±7 and 56±7 vs. 85±7 sec, pre- vs. post-exercise, P≤0.02; P=0.7 for sex × time interaction). In conclusion, this investigation demonstrated for the first time in older adults that: 1) FMD is enhanced following maximal exercise and 2) biological sex does not influence the FMD response to maximal exercise This work was supported by National Institute of Aging grant AG063143-01. 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.