The effects of endurance exercise in hypoxia on acid-base balance and potassium kinetics: a randomized crossover design in male endurance athletes

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Abstract

Background: 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. Methods: Nine trained middle-to-long distance athletes [maximal oxygen uptake (VO2max) 57.2 ± 1.0 mL/kg/min] completed two different trials on different days, consisting of exercise in moderate hypoxia [fraction of inspired oxygen (FiO2) = 14.5%, H trial] and exercise in normoxia (FiO2 = 20.9%, N trial). They performed interval endurance exercise (8 × 4 min pedaling at 80% of VO2max alternated with 2-min intervals of active rest at 40% of VO2max) 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. Results: 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). Conclusions: 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.

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Sumi, D., Kojima, C., Kasai, N., & Goto, K. (2018). The effects of endurance exercise in hypoxia on acid-base balance and potassium kinetics: a randomized crossover design in male endurance athletes. Sports Medicine - Open, 4(1). https://doi.org/10.1186/s40798-018-0160-1

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