Sumi Daichi, Kasai Nobukazu, Ito Hiroto, Goto Kazushige
Graduate School of Sports and Health Science, Ritsumeikan University, Kusatsu, Japan.
Faculty of Sports and Health Science, Ritsumeikan University, Kusatsu, Japan.
Front Physiol. 2019 May 16;10:504. doi: 10.3389/fphys.2019.00504. eCollection 2019.
To investigate the carbohydrate metabolism, acid-base balance, and potassium kinetics in response to exercise in moderate hypoxia among endurance athletes.
Nine trained endurance athletes [maximal oxygen uptake (VO): 62.5 ± 1.2 mL/kg/min] completed two different trials on different days: either exercise in moderate hypoxia [fraction of inspired oxygen (FiO) = 14.5%, HYPO] or exercise in normoxia (FiO = 20.9%, NOR). They performed a high-intensity interval-type endurance exercise consisting of 10 × 3 min runs at 90% of VO with 60 s of running (active rest) at 50% of VO between sets in hypoxia (HYPO) or normoxia (NOR). Venous blood samples were obtained before exercise and during the post-exercise. The subjects consumed C-labeled glucose immediately before exercise, and we collected expired gas samples during exercise to determine the C-excretion (calculated as CO/CO).
The running velocities were significantly lower in HYPO (15.0 ± 0.2 km/h) than in NOR (16.4 ± 0.3 km/h, < 0.0001). Despite the lower running velocity, we found a significantly greater exercise-induced blood lactate elevation in HYPO compared with in NOR ( = 0.002). The bicarbonate ion concentration ( = 0.002) and blood pH ( = 0.002) were significantly lower in HYPO than in NOR. There were no significant differences between the two trials regarding the exercise-induced blood potassium elevation ( = 0.87) or C-excretion (HYPO, 0.21 ± 0.02 mmol⋅39 min; NOR, 0.14 ± 0.03 mmol⋅39 min; = 0.10).
Endurance exercise in moderate hypoxia elicited a decline in blood pH. However, it did not augment the exercise-induced blood K elevation or exogenous glucose oxidation (C-excretion) compared with the equivalent exercise in normoxia among endurance athletes. The findings suggest that endurance exercise in moderate hypoxia causes greater metabolic stress and similar exercise-induced elevation of blood K and exogenous glucose oxidation compared with the same exercise in normoxia, despite lower mechanical stress (i.e., lower running velocity).
研究耐力运动员在中度低氧环境下运动时的碳水化合物代谢、酸碱平衡和钾动力学。
9名训练有素的耐力运动员[最大摄氧量（VO）：62.5±1.2 mL/kg/min]在不同日期完成两项不同试验：中度低氧环境下运动[吸入氧分数（FiO）=14.5%，低氧组（HYPO）]或常氧环境下运动（FiO=20.9%，常氧组（NOR））。他们进行了高强度间歇式耐力运动，包括在低氧组（HYPO）或常氧组（NOR）中以VO的90%进行10次3分钟跑步，每组之间以VO的50%进行60秒跑步（主动休息）。在运动前和运动后采集静脉血样。受试者在运动前立即摄入C标记的葡萄糖，并在运动期间收集呼出气体样本以测定C排泄量（计算为CO/CO）。
低氧组（HYPO）的跑步速度（15.0±0.2 km/h）显著低于常氧组（NOR）（16.4±0.3 km/h，<0.0001）。尽管跑步速度较低，但我们发现低氧组（HYPO）运动诱导的血乳酸升高幅度显著大于常氧组（NOR）（=0.002）。低氧组（HYPO）的碳酸氢根离子浓度（=0.002）和血液pH值（=0.002）显著低于常氧组（NOR）。在运动诱导的血钾升高（=0.87）或C排泄量方面，两项试验之间无显著差异（低氧组（HYPO），0.21±0.02 mmol·39 min；常氧组（NOR），0.14±0.03 mmol·39 min；=0.10）。
中度低氧环境下的耐力运动导致血液pH值下降。然而，与耐力运动员在常氧环境下进行的同等运动相比，它并未增强运动诱导的血钾升高或外源性葡萄糖氧化（C排泄量）。研究结果表明，尽管机械应力较低（即跑步速度较低），但中度低氧环境下的耐力运动与常氧环境下的相同运动相比，会导致更大的代谢应激以及类似的运动诱导的血钾升高和外源性葡萄糖氧化。
