Aging is associated with attenuated blood flow and vasodilator responses during rhythmic exercise. Older adults also demonstrate attenuated blood flow and vasodilator responses following single skeletal muscle contractions (contraction-induced rapid onset vasodilation, ROV) within the forearm. These age-associated attenuations within the forearm have been demonstrated to be a result of endothelial and neural mechanisms. The objective of this research was to examine: 1) whether age-associated attenuations within the forearm are from mechanical factors; 2) whether age-associated attentions in ROV are present within the leg, as well as explore potential mechanisms for these age-associated attenuations in ROV; 3) examine whether aging is associated with a slower rate of adjustment in vasodilation (vasodilator kinetics) during rhythmic exercise preceding steady-state exercise; and 4) examine approaches to ameliorate age-related attenuations in blood flow and vasodilation within the leg across the entire exercise transient (onset to steady-state).
The novel findings of this research are that 1) age-associated attenuations in ROV within the forearm are independent of mechanical factors; 2) older adults demonstrate attenuated ROV responses within the leg; 3) age-related attenuations in ROV within the leg are not explained by enhanced sympathetic adrenergic vasoconstriction; 4) older adults exhibit prolonged vasodilator kinetics preceding steady-state exercise; and 5) when examined in a cross-sectional design chronic exercise training improves ROV, vasodilator kinetics, as well as steady-state blood flow and vasodilator responses in older adults; 6) acute supplementation with dietary nitrate fails to exert any effect on blood flow and vasodilator responses during any domain of exercise. Collectively, this work establishes that aging is associated with reductions in blood flow and vasodilation across the entire exercise transient (onset to steady-state) within the leg, which is offset by chronic exercise training. Mechanistically, the current data suggests that mechanical and sympathetic factors do not explain age-related reductions in ROV in the arm and leg, respectively. Furthermore, acute supplementation of dietary nitrate does not impact leg blood flow and vasodilator responses in older adults during any domain of the exercise transient.