Shotaro Kawakami1, Tetsuhiko Yasuno2, Takuro Matsuda3, Kanta Fujimi3, Ai Ito4, Saki Yoshimura4, Yoshinari Uehara5,6, Hiroaki Tanaka5,6, Takao Saito2, Yasuki Higaki7,8. 1. Department of Rehabilitation, Fukuoka University Chikushi Hospital, 1-1-1 Zokumyoin, Chikushino, Fukuoka, 818-0067, Japan. 2. Division of Nephrology and Rheumatology, Department of Internal Medicine, Fukuoka University School of Medicine, 7-45-1 Nanakuma, Johnan-ku, Fukuoka, 814-0133, Japan. 3. Department of Rehabilitation, Fukuoka University Hospital, 7-45-1 Nanakuma, Johnan-ku, Fukuoka, 814-0133, Japan. 4. Graduate School of Sports and Health Science, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka, 814-0180, Japan. 5. Laboratory of Exercise Physiology, Faculty of Health and Sports Science, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka, 814-0180, Japan. 6. The Fukuoka University Institute for Physical Activity, 8-19-1 Nanakuma, Johnan-ku, Fukuoka, 814-0180, Japan. 7. Laboratory of Exercise Physiology, Faculty of Health and Sports Science, Fukuoka University, 8-19-1 Nanakuma, Johnan-ku, Fukuoka, 814-0180, Japan. higaki@fukuoka-u.ac.jp. 8. The Fukuoka University Institute for Physical Activity, 8-19-1 Nanakuma, Johnan-ku, Fukuoka, 814-0180, Japan. higaki@fukuoka-u.ac.jp.
Abstract
BACKGROUND: High-intensity exercise reduces renal blood flow (RBF) and may transiently exacerbate renal dysfunction. RBF has previously been measured invasively by administration of an indicator material; however, non-invasive measurement is now possible with technological innovations. This study examined variations in RBF at different exercise intensities using ultrasound echo. METHODS: Eight healthy men with normal renal function (eGFRcys 114 ± 19 mL/min/1.73 m2) participated in this study. Using a bicycle ergometer, participants underwent an incremental exercise test using a ramp protocol (20 W/min) until exhaustion in Study 1 and the lactate acid breaking point (LaBP) was calculated. Participants underwent a multi-stage test at exercise intensities of 60, 80, 100, 120, and 140% LaBP in Study 2. RBF was measured by ultrasound echo at rest and 5 min after exercise in Study 1 and at rest and immediately after each exercise in Study 2. To determine the mechanisms behind RBF decline, a catheter was placed into the antecubital vein to study vasoconstriction dynamics. RESULTS: RBF after maximum exercise decreased by 51% in Study 1. In Study 2, RBF showed no significant decrease until 80% LaBP, and showed a significant decrease (31%) at 100% LaBP compared with at rest (p < 0.01). The sympathetic nervous system may be involved in this reduction in RBF. CONCLUSIONS: RBF showed no significant decrease until 80% LaBP, and decreased with an increase in blood lactate. Reduction in RBF with exercise above the intensity at LaBP was due to decreased cross-sectional area rather than time-averaged flow velocity.
BACKGROUND: High-intensity exercise reduces renal blood flow (RBF) and may transiently exacerbate renal dysfunction. RBF has previously been measured invasively by administration of an indicator material; however, non-invasive measurement is now possible with technological innovations. This study examined variations in RBF at different exercise intensities using ultrasound echo. METHODS: Eight healthy men with normal renal function (eGFRcys 114 ± 19 mL/min/1.73 m2) participated in this study. Using a bicycle ergometer, participants underwent an incremental exercise test using a ramp protocol (20 W/min) until exhaustion in Study 1 and the lactate acid breaking point (LaBP) was calculated. Participants underwent a multi-stage test at exercise intensities of 60, 80, 100, 120, and 140% LaBP in Study 2. RBF was measured by ultrasound echo at rest and 5 min after exercise in Study 1 and at rest and immediately after each exercise in Study 2. To determine the mechanisms behind RBF decline, a catheter was placed into the antecubital vein to study vasoconstriction dynamics. RESULTS: RBF after maximum exercise decreased by 51% in Study 1. In Study 2, RBF showed no significant decrease until 80% LaBP, and showed a significant decrease (31%) at 100% LaBP compared with at rest (p < 0.01). The sympathetic nervous system may be involved in this reduction in RBF. CONCLUSIONS: RBF showed no significant decrease until 80% LaBP, and decreased with an increase in blood lactate. Reduction in RBF with exercise above the intensity at LaBP was due to decreased cross-sectional area rather than time-averaged flow velocity.
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