Sex impacts the flow-mediated dilation response to acute aerobic exercise in older adults

There is growing evidence of sex differences in the chronic effect of aerobic exercise on endothelial function (flow-mediated dilation; FMD) in older adults, but whether there are sex differences also in the acute effect of aerobic exercise on FMD in older adults is unknown. The purpose of this study was to test the hypothesis that sex modulates the FMD response to acute aerobic exercise in older adults. Thirteen older men and fifteen postmenopausal women (67 ± 1 vs. 65 ± 2 years, means ± SE, P = 0.6), non-smokers, free of major clinical disease, participated in this randomized crossover study. Brachial artery FMD was measured: 1) prior to exercise; 2) 20 min after a single bout of high-intensity interval training (HIIT; 40 min; 4 × 4 intervals 90% peak heart rate (HRpeak)), moderate-intensity continuous training (MICT; 47 min 70% HRpeak) and low-intensity continuous training (LICT; 47 min 50% HRpeak) on treadmill; and 3) following 60-min recovery from exercise. In older men, FMD was attenuated by 45% following HIIT (5.95 ± 0.85 vs. 3.27 ± 0.52%, P = 0.003) and by 37% following MICT (5.97 ± 0.87 vs. 3.73 ± 0.47%, P = 0.03; P = 0.9 for FMD response to HIIT vs. MICT) and was normalized following 60-min recovery (P = 0.99). In postmenopausal women, FMD did not significantly change in response to HIIT (4.93 ± 0.55 vs. 6.31 ± 0.57%, P = 0.14) and MICT (5.32 ± 0.62 vs. 5.60 ± 0.68%, P = 0.99). In response to LICT, FMD did not change in postmenopausal women nor older men (5.21 ± 0.64 vs. 6.02 ± 0.73%, P = 0.7 and 5.70 ± 0.80 vs. 5.55 ± 0.67%, P = 0.99). In conclusion, sex and exercise intensity influence the FMD response to acute aerobic exercise in older adults.