Abstract
BackgroundExercise-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.MethodsNine 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.ResultsThe 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).ConclusionsHigh-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.
Highlights
Exercise-induced disturbance of acid-base balance and accumulation of extracellular potassium (K+) are suggested to elicit fatigue
The VO2max and exercise intensity >VO2max was significantly lower in the H trial (41.7 ± 2.2 mL/kg/min) than in the N trial (57.2 ± 2.9 mL/kg/min, P < 0.0001)
Exercise-induced blood lactate elevations were significantly greater in the N trial than in the H trial
Summary
Exercise-induced disturbance of acid-base balance and accumulation of extracellular potassium (K+) are suggested to elicit fatigue. Sumi et al Sports Medicine - Open (2018) 4:45 hypoxic conditions triggers lower systemic oxygen uptake [5] and arterial oxygen saturation [6], whereas carbohydrate utilization [7, 8] and exercise-induced blood lactate levels [9, 10] are augmented. These specific responses during exercise under hypoxic conditions may trigger improvement of exercise performance and promote peripheral adaptation in the muscles. The exercise-induced kinetics of blood HCO3− reflect the homeostasis of acid-base balance in the blood during intensive exercise
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
