Purpose The aim of this study was to determine how sodium hydrogen carbonate (NaHCO3) ingestion during a 1-h recovery period after a 200-m front-crawl swim affects blood-gas levels, acid-base balance, and performance during a successive trial. Methods Fourteen national-level male swimmers (age: 21 ± 3 years, body mass (BM):77 ± 10 kg, stature: 181 ± 7 cm) performed four maximal 200-m front-crawl tests. On one of the two days, the swimmers swam two 200-m tests with a 1-h recovery break, during which they drank water (WATER); on the other day, they performed the same protocol but consumed 0.3 g min-1 NaHCO3 solution during the recovery break (NaHCO3). Results The ingestion of NaHCO3 before the second test had no effect on swim time despite a greater [HCO3-] (19.2 ± 2.3 mmol L-1) than that measured during the first test (NaHCO3) (14.5 ± 1.1 mmol L-1) and the other two tests (WATER) (12.7 ± 2.4 and 14.8 ± 1.5 mmol L-1; F = 18.554; p = 0.000) and a higher blood pH (7.46 ± 0.03) than that measured during the first test (NaHCO3) (7.39 ± 0.02) and the other two tests (WATER) (7.16 ± 0.04 and 7.20 ± 0.05); (F = 5.255; p = 0.004). An increase in blood pCO2 (0.2 ± 0.3 kPa) between both tests (NaHCO3) compared to unchanged pCO2 values (- 0.1 ± 0.3 kPa) between the other two tests (WATER) (t = - 2.984; p = 0.011; power = 0.741) was confirmed. Conclusions NaHCO3 ingestion during the recovery period between two 200-m front-crawl time trials had a strong buffering effect that did not positively affect performance. An increase in pCO2 may have counterbalanced this impact.
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