The Influence Of Habitual Moderate-Vigorous Physical Activity Levels Versus Aerobic Fitness On Age-Related Endothelial Function

Older adults (OA) have reduced vascular function, as assessed via flow-mediated dilation (FMD). However, it is unknown whether OA also have reduced low flow-mediated constrictor (L-FMC) responses than younger adults (YA). Further, we have previously demonstrated in OA that FMD responses are influenced more by habitual moderate-vigorous physical activity (MVPA) levels than aerobic fitness. It is unclear whether differences in habitual MVPA levels between YA and OA contribute to age-related declines in vascular function. PURPOSE: To test the hypotheses that: 1) YA would have superior brachial (BA) and popliteal (POP) FMD and L-FMC versus OA, and 2) that habitual MVPA levels would have a greater influence on endothelial function than age- and sex- aerobic fitness levels. METHODS: FMD and L-FMC were measured via duplex ultrasonography in 9 YA (5♀, 24±3 yr) and 9 OA (5♀, 68±4 yr) matched for body mass index, as well as age- and sex-related aerobic fitness categories (Poor-Excellent). L-FMC and FMD were quantified as the percent decrease in diameter (from baseline) during the last 30-s of a 5-min distal cuff occlusion and the percent increase in diameter during a 5-min post-cuff deflation period, respectively. Peak oxygen consumption was measured via indirect calorimetry using an incremental cycle ergometer test. MVPA was quantified over at least 7-d using a PiezoRx® physical activity monitor. RESULTS: Compared to OA, YA spent more time engaged in MVPA (426±178 vs. 260±91 min/week, p= 0.03), had higher BA-FMD (8.0±2.8 vs. 5.6±1.7%, p= 0.04) and POP-FMD (5.8±0.8 vs. 3.2±1.2 %, p< 0.01). However, both groups had similar BA L-FMC (YA, -1.5±1.7 vs. OA, -0.8±1.1%, p= 0.35) and POP L-FMC responses (YA, -1.7±1.7 vs. OA, -0.6±1.9%, p= 0.19). MVPA was moderately correlated to BA-FMD (r= 0.64, p< 0.01) and POP-FMD (r=0.53, p= 0.03). However, age-/sex-specific aerobic fitness categories were not correlated to BA-FMD (p= 0.28) or POP-FMD (p= 0.30). CONCLUSION: Based on age- and sex-related aerobic fitness categories, our results suggest that lower weekly MVPA time may have a greater influence on age-related declines in endothelial-dependent vasodilation than aerobic fitness status per se. However, neither BA nor POP endothelial-dependent vasoconstrictor responses were altered with aging.