Effects of Exercise Around the Ventilation Threshold on Renal Blood Flow in Healthy Individuals

Purpose High-intensity exercise reduces renal artery blood flow (RBF) compared to other forms of exercise. However, it is unclear whether moderate-intensity exercise, including those at the ventilation threshold (VT), decreases RBF. Additionally, attenuated renal autoregulation and associated blood flow can cause renal injury in patients with underlying disease. Therefore, this study aimed to confirm the changes in RBF after moderate-level exercise in healthy subjects, which will have implications for the study of renal arterial blood flow in patients with renal failure.Methods Cardiopulmonary exercise tests were performed by 10 healthy male participants (mean age, 31 +/- 8 years): 3 min constant work-rate exercise tests, varying in exercise intensity 1 min before VT (pre-VT), after VT (post-VT), and after the respiratory compensation point (RCP). The RBF was measured using ultrasonic inspection equipment following each exercise. The VT was determined using the ventilatory equivalent method (VEQ method), while the RBF was calculated from the time-averaged flow velocity (TAV) and crosssectional area (CSA).Results At baseline (resting phase), RBF was 461 +/- 142 mL/min. While RBFs at pre-VT were not significantly different from those at baseline (482 +/- 142 mL/min; P = 0.82), significant differences were observed at post-VT (289 +/- 111 mL/min; P < 0.01 vs. baseline). RBFs at the RCP were also different from those at the baseline (212 +/- 56 mL/min; P < 0.01 vs. baseline).Conclusions In healthy individuals, exercises varying in intensity up to the vicinity of the VT can be performed without any significant decrease in RBF.