Sumi Daichi, Kojima Chihiro, Kasai Nobukazu, Goto Kazushige
Graduate School of Sports and Health Science, Ritsumeikan University, Kusatsu, Shiga, Japan.
Faculty of Sports and Health Science, Ritsumeikan University, 1-1-1, Nojihigashi, Kusatsu, Shiga, 525-8577, Japan.
Sports Med Open. 2018 Oct 13;4(1):45. doi: 10.1186/s40798-018-0160-1.
Exercise-induced disturbance of acid-base balance and accumulation of extracellular potassium (K) are suggested to elicit fatigue. Exercise under hypoxic conditions may augment exercise-induced alterations of these two factors compared with exercise under normoxia. In the present study, we investigated acid-base balance and potassium kinetics in response to exercise under moderate hypoxic conditions in endurance athletes.
Nine trained middle-to-long distance athletes [maximal oxygen uptake (VO) 57.2 ± 1.0 mL/kg/min] completed two different trials on different days, consisting of exercise in moderate hypoxia [fraction of inspired oxygen (FO) = 14.5%, H trial] and exercise in normoxia (FO = 20.9%, N trial). They performed interval endurance exercise (8 × 4 min pedaling at 80% of VO alternated with 2-min intervals of active rest at 40% of VO) under hypoxic or normoxic conditions. Venous blood samples were obtained to determine blood lactate, pH, bicarbonate ion, and K concentrations before exercise, during exercise, and after exercise.
The blood lactate concentrations increased significantly with exercise in both trials. Exercise-induced blood lactate elevations were significantly greater in the N trial than in the H trial at all time points (P = 0.012). Bicarbonate ion concentrations (P = 0.001) and blood pH (P = 0.019) during exercise and post-exercise periods were significantly lower in the N trial than in the H trial. A significantly greater exercise-induced elevation in blood K concentration was produced in the N trial than in the H trial during exercise and immediately after exercise (P = 0.03).
High-intensity interval exercise on a cycle ergometer under moderate hypoxic conditions did not elicit a decrease in blood pH or elevation in K levels compared with an equivalent level of exercise under normoxic conditions.
运动引起的酸碱平衡紊乱和细胞外钾（K）的积累被认为会引发疲劳。与常氧运动相比，低氧条件下的运动可能会加剧这两个因素的运动诱导变化。在本研究中，我们调查了耐力运动员在中度低氧条件下运动时的酸碱平衡和钾动力学。
九名训练有素的中长跑运动员[最大摄氧量（VO）57.2±1.0 mL/kg/min]在不同日期完成了两项不同的试验，包括中度低氧运动[吸入氧分数（FO）=14.5%，H试验]和常氧运动（FO=20.9%，N试验）。他们在低氧或常氧条件下进行间歇耐力运动（8×4分钟以VO的80%蹬踏，与以VO的40%进行2分钟的主动休息间隔交替）。在运动前、运动期间和运动后采集静脉血样，以测定血乳酸、pH值、碳酸氢根离子和K浓度。
在两项试验中，血乳酸浓度均随运动显著增加。在所有时间点，运动诱导的血乳酸升高在N试验中均显著高于H试验（P=0.012）。运动期间和运动后，N试验中的碳酸氢根离子浓度（P=0.001）和血pH值（P=0.019）显著低于H试验。在运动期间和运动后立即，N试验中运动诱导的血K浓度升高显著高于H试验（P=0.03）。
与常氧条件下同等强度的运动相比，在中度低氧条件下进行的高强度间歇自行车运动不会引起血pH值下降或K水平升高。
