Myles W O'Brien1, Said Mekary2, Susan A Robinson1, Jarrett A Johns1, Derek Stephen Kimmerly3. 1. Autonomic Cardiovascular Control and Exercise Laboratory, School of Health and Human Performance, Division of Kinesiology, Faculty of Health, Dalhousie University, 6230 South Street, Halifax, NS, B3H 4R2, Canada. 2. School of Kinesiology, Acadia University, Wolfville, NS, Canada. 3. Autonomic Cardiovascular Control and Exercise Laboratory, School of Health and Human Performance, Division of Kinesiology, Faculty of Health, Dalhousie University, 6230 South Street, Halifax, NS, B3H 4R2, Canada. dskimmerly@dal.ca.
Abstract
PURPOSE: 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. METHODS: 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. RESULTS: 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%). CONCLUSIONS: 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.
PURPOSE: 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. METHODS: 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. RESULTS: 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%). CONCLUSIONS: 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.
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