BACKGROUND: Vascular conductance refers to the ease with which blood flows through arteries. Vascular conductance is reduced with aging due to impairments of vascular structure (i.e., arterial stiffness and wall thickening) and function. Reduction in renal blood flow demonstrates an increase in blood pressure (BP) which contributes to the pathogenesis of hypertension. Habitual exercise reduces age-related declines in vascular function. Whether chronic ultra-endurance training offsets age-associated reductions in vascular conductance is largely unexplored. Therefore, we evaluated associations between age and kidney vascular conductance in ultra-marathon runners aged 22-66 years. METHODS: Thirty-nine ultra-marathon runners competing in the 2023 Western States 100-mile Endurance Run were included in this analysis (33 M/6 F, 41 ± 10 years, BMI: 23 ± 2 kg/m2; mean ± SD). Kidney blood velocity in the renal and segmental arteries was measured in the decubitus position using a GE Logiq e ultrasound (3 - 5 mHz). We measured supine brachial and central blood pressure using SphygmoCor XCEL. Renal and segmental artery conductance were calculated as blood velocity divided by central mean BP (cm●s-1/mmHg). All data were normally distributed (Shapiro-Wilk test, ps > 0.05). We conducted Pearson’s r correlations between age and kidney vascular conductance and kidney blood velocity with α set at ≤ 0.05. RESULTS: Central mean BP in our sample was 92 ± 8 mmHg. Age was not associated with renal (0.58 ± 0.13 cm●s-1/mmHg; r = -0.243, p = 0.137) or segmental (0.35 ± 0.08 cm●s-1/mmHg; r = -0.239, p = 0.160) artery vascular conductance. Similarly, when central BP was not accounted for, age was not associated with renal (53 ± 12 cm●s-1; r = -0.086, p = 0.603) or segmental (32 ± 7 cm●s-1; r = -0.055, p = 0.748) artery velocity. CONCLUSIONS: While additional data in a larger sample size and age-matched control participants are needed, our data indicate that age is not associated with reduced resting kidney vascular conductance or blood velocity in ultra-marathon runners.

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