The relationship between aerobic fitness and low-flow-mediated constriction in older adults

Aerobic fitness is directly related to favorable vasodilatory (i.e., flow-mediated dilation; FMD) and vasoconstrictor functions (i.e., low-flow-mediated constriction; L-FMC) in young adults. Furthermore, aerobically fit older adults (OA) have larger FMD responses than their less fit peers. However, the relationship between aerobic fitness and vasoconstrictor responsiveness is unknown in OA. We hypothesized that OA who are more aerobically fit will exhibit a greater L-FMC response than their less fit counterparts.

Forty-seven healthy OA (67 ± 5 years) were divided into less (LF; n = 27) and more aerobically fit (MF; n = 20) groups based on peak oxygen consumption (VO₂peak). VO₂peak was determined from an incremental maximal cycle ergometer test via indirect calorimetry. FMD and L-FMC were assessed in the brachial artery via high-resolution duplex ultrasonography.

VO₂peak (18.3 ± 3.2 versus 29.1 ± 5.8 ml/kg/min; P < 0.001) and L-FMC were both greatest in the MF versus LF groups (-1.2 ± 0.9 vs. - 0.5 ± 0.6%; P = 0.01). Furthermore, the MF group had an enhanced FMD response (5.6 ± 1.5 versus 3.9 ± 1.2%; P < 0.001). In the pooled sample, there was a negative correlation (r = - 0.52; P < 0.001) between VO₂peak (22.9 ± 7.0 ml/kg/min) and L-FMC (-0.8 ± 0.8%).

In an older population, greater aerobic fitness was associated with a more favorable vasoconstrictor response to low-flow conditions. Interventional or longitudinal aerobic exercise training studies are warranted in this population to determine the impact of training-induced increases in VO₂peak on L-FMC.