There is growing evidence of sex differences in the chronic effect of aerobic exercise on endothelial function (flow-mediated dilation; FMD) in older adults. However, whether sex differences also exist in the acute effect of aerobic exercise on FMD in older adults is unknown.
PURPOSE: To test the hypothesis that the FMD response to acute aerobic exercise will be different in older men compared with postmenopausal women and that exercise intensity will influence the FMD response.
METHODS: Thirteen older men and fifteen postmenopausal women, free of major clinical disease, participated in this randomized crossover study (67±1 vs. 65±2 yrs, mean±SE, P=0.4). Subjects completed a single bout of low-intensity continuous training (LICT; 47 min 50% peak heart rate (HRpeak)), moderate-intensity continuous training (MICT; 47 min 70% HRpeak) and high-intensity interval training (HIIT; 40 min: alternating intensities of 90% and 70% HRpeak) on the treadmill in a counterbalanced order. Brachial artery FMD was assessed at rest, at end of exercise and following 60-minute recovery.
RESULTS: 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).
CONCLUSIONS: Sex and exercise intensity significantly impact the FMD response to acute aerobic exercise in older adults. In older men, FMD is attenuated following acute HIIT and MICT but not LICT, whereas in postmenopausal women FMD is unaffected.