Effects of endurance exercise under hypoxia on acid-base and ion balance in healthy males

[PURPOSE]: This study was performed to investigate the acid-base and ion balance at rest and after exercise in healthy males under normoxia, moderate hypoxia, and severe hypoxia. [METHODS]: Ten healthy Korean males completed three different trials on different days, comprising exercise under normoxia (F(i)O(2) = 20.9%, N trial), moderate hypoxia (F(i)O(2) = 16.5%, MH trial), and severe hypoxia (F(i)O(2) = 12.8%, SH trial). They undertook endurance exercise for 30 min on a cycle ergometer at the same relative exercise intensity equivalent to 80% maximal heart rate under all conditions. Capillary blood samples were obtained to determine acid-base and ion balance at rest and after exercise. [RESULTS]: Exercise-induced blood lactate elevations were significantly increased as hypoxic conditions became more severe; SH > MH > N trials (P = 0.003). After exercise, blood glucose levels were significantly higher in the SH trial than in the N and MH trials (P = 0.001). Capillary oxygen saturation (S(C)O(2)) levels were significantly lowered as hypoxic conditions became more severe; SH > MH > N trials (P < 0.001). The pH levels were significantly lower in the MH trial than that in the N trial (P = 0.010). Moreover, H(C)O(3)- levels were significantly lower in the SH trial than in the N trial, with significant interaction (P = 0.003). There were no significant differences in blood Na(+), K(+), and Ca(2+) levels between the trials. [CONCLUSION]: MH and SH trials induced greater differences in glucose, lactate, S(C)O(2), pH, and H(C)O(3)- levels in capillary blood compared to the N trial. Additionally, lactate, S(C)O(2), and H(C)O(3)- levels showed greater changes in the SH trial than in the MH trial. However, there were no significant differences in Na(+), K(+), and Ca(2+) levels in MH and SH trials compared to the N trial.