The time to peak blood bicarbonate (HCO 3 − ), pH, and strong ion difference (SID) following sodium bicarbonate (NaHCO 3 ) ingestion in highly trained adolescent swimmers

Abstract Background Contemporary research suggests that the optimal timing of sodium bicarbonate (NaHCO 3 ) should be based upon an individual time in which bicarbonate (HCO 3 − ) or pH peaks within the blood. However, the mechanisms surrounding acidosis on exercise performance are contested, therefore it is plausible that the ergogenic effects of NaHCO 3 are instead a result of an increased strong ion difference (SID) following ingestion. Since the post-ingestion time course of the SID is currently unknown, the purpose of this study was to investigate the pharmacokinetics of the SID in direct comparison to HCO 3 − and pH. Methods Twelve highly trained, adolescent swimmers (age: 15.9 ± 1.0 yrs, body mass: 65.3 ± 9.6 kg) consumed their typical pre-competition nutrition before ingesting 0.3 g·kg BM -1 NaHCO 3 in gelatine capsules. Capillary blood samples were then taken during quiet, seated rest on nine occasions (0, 60, 75, 90, 105, 120, 135, 150, and 165 min post-ingestion) for the assessment of time course changes in HCO 3 − , pH, and the SID. Results On a group mean level, no differences were found in the time in which each variable peaked within the blood (HCO 3 − = 130 ± 35 min, pH = 120 ± 38 min, SID = 96 ± 35 min; p = 0.06). A large effect size was calculated between the timing of peak HCO 3 − and the SID ( g = 0.91), however, suggesting that a difference may occur between these two measures in practice. Conclusions A time difference between peak HCO 3 − and the SID presents an interesting avenue for further research since an approach based upon individual increases in extracellular SID has yet to be investigated. Future studies should therefore compare these dosing strategies directly to elucidate whether either one is more ergogenic for exercise performance.