The influence of alkalosis on repeated high-intensity exercise performance and acid-base balance recovery in acute moderate hypoxic conditions

PurposeExacerbated hydrogen cation (H+) production is suggested to be a key determinant of fatigue in acute hypoxic conditions. This study, therefore, investigated the effects of NaHCO3 ingestion on repeated 4km TT cycling performance and post-exercise acid-base balance recovery in acute moderate hypoxic conditions.MethodsTen male trained cyclists completed four repeats of 2x4km cycling time trials (TT1 and TT2) with 40min passive recovery, each on different days. Each TT series was preceded by supplementation of one of the 0.2gkg(-1) BM NaHCO3 (SBC2), 0.3gkg(-1) BM NaHCO3 (SBC3), or a taste-matched placebo (0.07gkg(-1) BM sodium chloride; PLA), administered in a randomized order. Supplements were administered at a pre-determined individual time to peak capillary blood bicarbonate concentration ([HCO3-]). Each TT series was also completed in a normobaric hypoxic chamber set at 14.5% FiO(2) (similar to 3000m).ResultsPerformance was improved following SBC3 in both TT1 (400.224.1 vs. 405.9 +/- 26.0s; p=0.03) and TT2 (407.2 +/- 29.2 vs. 413.2 +/- 30.8s; p=0.01) compared to PLA, displaying a very likely benefit in each bout. Compared to SBC2, a likely and possible benefit was also observed following SBC3 in TT1 (402.3 +/- 26.5s; p=0.15) and TT2 (410.3 +/- 30.8s; p=0.44), respectively. One participant displayed an ergolytic effect following SBC3, likely because of severe gastrointestinal discomfort, as SBC2 still provided ergogenic effects.Conclusion NaHCO3 ingestion improves repeated exercise performance in acute hypoxic conditions, although the optimal dose is likely to be 0.3gkg(-1) BM.