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

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.

Keywords

  • Hypoxia
  • Endurance exercise
  • Acid-base balance
  • Potassium

Key points

  • High-intensity interval exercise on a cycle ergometer under moderate hypoxic conditions did not elicit the decline of blood pH compared with an equivalent level of exercise under normoxic conditions.

  • Exercise-induced elevations in blood lactate concentrations were significantly greater in normoxia than in hypoxia.

  • The exercise under moderate hypoxic conditions did not elicit the K+ elevation compared with the exercise under normoxic conditions. 


Autor / Fonte:Daichi Sumi, Chihiro Kojima, Nobukazu Kasai, Kazushige Goto Sports Medicine—Open 2018 October 13, 4 (1): 45
Link: https://sportsmedicine-open.springeropen.com/articles/10.1186/s40798-018-0160-1