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) has demonstrated good to excellent reproducibility following ingestion of both 0.2 g kg body mass (BM) and 0.3 g kg BM sodium bicarbonate (NaHCO), but the consistency of the time trial (TT) performance response using such an individualised NaHCO ingestion strategy remains unknown. This study therefore evaluated the reproducibility of 4-km TT performance following NaHCO 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 (SBC2) or 0.3 g kg BM (SBC3) NaHCO, 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) and lactate [La]. RESULTS Alkalosis was achieved prior to exercise in both SBC2 and SBC3, as pH and HCO were greater compared to baseline (p 0.05). The reproducibility of the mean absolute change from baseline to peak in HCO 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 ingestion, which is due to the high reproducibility of blood acid-base variables with repeat administration of NaHCO. Using a time to peak HCO 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 to mitigate gastrointestinal (GI) discomfort