The timing of sodium bicarbonate (NaHCO.sub.3) supplementation has been suggested to be most optimal when coincided with a personal time that bicarbonate (HCO.sub.3 .sup.-) or pH peaks in the blood following ingestion. However, the ergogenic mechanisms supporting this ingestion strategy are strongly contested. It is therefore plausible that NaHCO.sub.3 may be ergogenic by causing beneficial shifts in the strong ion difference (SID), though the time course of this blood acid base balance variable is yet to be investigated. Twelve highly trained, adolescent swimmers (age: 15.9 ± 1.0 years, body mass: 65.3 ± 9.6 kg) consumed their typical pre-competition nutrition 1-3 hours before ingesting 0.3 gâkg BM.sup.-1 NaHCO.sub.3 in gelatine capsules. Capillary blood samples were then taken during seated rest on nine occasions (0, 60, 75, 90, 105, 120, 135, 150, 165 min post-ingestion) to identify the time course changes in HCO.sub.3 .sup.-, pH, and the SID. No significant differences were found in the time to peak of each blood measure (HCO.sub.3 .sup.- : 130 ± 35 min, pH: 120 ± 38 min, SID: 98 ± 37 min; p = 0.08); however, a large effect size was calculated between time to peak HCO.sub.3 .sup.- and the SID (g = 0.88). Considering that a difference between time to peak blood HCO.sub.3 .sup.- and the SID was identified in adolescents, future research should compare the ergogenic effects of these two individualized NaHCO.sub.3 ingestion strategies compared to a traditional, standardized approach.