The Reproducibility of 4-km Time Trial (TT) Performance Following Individualised Sodium Bicarbonate Supplementation: a Randomised Controlled Trial in Trained Cyclists

BACKGROUND: Individual time to peak blood bicarbonate (HCO(3) (−)) has demonstrated good to excellent reproducibility following ingestion of both 0.2 g kg(−1) body mass (BM) and 0.3 g kg(−1) BM sodium bicarbonate (NaHCO(3)), but the consistency of the time trial (TT) performance response using such an individualised NaHCO(3) ingestion strategy remains unknown. This study therefore evaluated the reproducibility of 4-km TT performance following NaHCO(3) ingestion individualised to time to peak blood bicarbonate. METHODS: Eleven trained male cyclists completed five randomised treatments with prior ingestion of 0.2 g kg(−1) (SBC2) or 0.3 g kg(−1) BM (SBC3) NaHCO(3), on two separate occasions each, or a control trial entailing no supplementation. Participants completed a 4-km cycling TT on a Velotron ergometer where time to complete, power and speed were measured, whilst acid-base blood parameters were also recorded (pH and blood bicarbonate concentration HCO(3) (−)) and lactate [La(−)]. RESULTS: Alkalosis was achieved prior to exercise in both SBC2 and SBC3, as pH and HCO(3) (−) were greater compared to baseline (p < 0.001), with no differences between treatments (p > 0.05). The reproducibility of the mean absolute change from baseline to peak in HCO(3) (−) was good in SBC2 (r = 0.68) and excellent in SBC3 (r = 0.78). The performance responses following both SBC2 and SBC3 displayed excellent reproducibility (r range = 0.97 to 0.99). CONCLUSIONS: Results demonstrate excellent reproducibility of exercise performance following individualised NaHCO(3) ingestion, which is due to the high reproducibility of blood acid-base variables with repeat administration of NaHCO(3). Using a time to peak HCO(3) (-) strategy seems to cause no dose-dependent effects on performance for exercise of this duration and intensity; therefore, athletes may consider smaller doses of NaHCO(3) to mitigate gastrointestinal (GI) discomfort.