The Reproducibility of Blood Acid Base Responses in Male Collegiate Athletes Following Individualised Doses of Sodium Bicarbonate: A Randomised Controlled Crossover Study

Background: Current evidence suggests sodium bicarbonate (NaHCO ₃) should be ingested based upon the individualised alkalotic peak of either blood pH or bicarbonate (HCO ₃ ⁻) because of large inter-individual variations (10–180 min). If such a strategy is to be practical, the blood analyte response needs to be reproducible. Objective: This study aimed to evaluate the degree of reproducibility of both time to peak (TTP) and absolute change in blood pH, HCO ₃ ⁻ and sodium (Na ⁺) following acute NaHCO ₃ ingestion. Methods: Male participants (n = 15) with backgrounds in rugby, football or sprinting completed six randomised treatments entailing ingestion of two doses of 0.2 g·kg ⁻¹ body mass (BM) NaHCO ₃ (SBC2a and b), two doses of 0.3 g·kg ⁻¹ BM NaHCO ₃ (SBC3a and b) or two control treatments (CON1a and b) on separate days. Blood analysis included pH, HCO ₃ ⁻ and Na ⁺ prior to and at regular time points following NaHCO ₃ ingestion over a 3-h period. Results: HCO ₃ ⁻ displayed greater reproducibility than pH in intraclass correlation coefficient (ICC) analysis for both TTP (HCO ₃ ⁻ SBC2 r = 0.77, P = 0.003; SBC3 r = 0.94, P < 0.001; pH SBC2 r = 0.62, P = 0.044; SBC3 r = 0.71, P = 0.016) and absolute change (HCO ₃ ⁻ SBC2 r = 0.89, P < 0.001; SBC3 r = 0.76, P = 0.008; pH SBC2 r = 0.84, P = 0.001; SBC3 r = 0.62, P = 0.041). Conclusion: Our results indicate that both TTP and absolute change in HCO ₃ ⁻ is more reliable than pH. As such, these data provide support for an individualised NaHCO ₃ ingestion strategy to consistently elicit peak alkalosis before exercise. Future work should utilise an individualised NaHCO ₃ ingestion strategy based on HCO ₃ ⁻ responses and evaluate effects on exercise performance.