The effects of sodium hydrogen carbonate ingestion during the recovery period between two 200-m front-crawl time trials

Abstract

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 [ ${\mathrm{HCO}}_3^{-}$ ] (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.

Keywords: Acidosis; Acid–base balance; Blood alkalosis; Blood gases.

Fig. 1

Design of the experiment. The experiment consisted of two drinking solution conditions. The WATER condition consisted of two 200-m tests separated by a 1-h recovery break with water ingestion. Blood samples were taken before and after each trial. Another condition (NaHCO₃) consisted of two 200-m tests, separated by a 1-h recovery break with the ingestion of NaHCO₃ solution. As with the WATER, blood samples were taken before and after each 200-m test

Fig. 2

pCO₂ values during the first minute of the first and second 200-m test with water ingestion and the first and second 200-m test with NaHCO₃ ingestion. The results show a clear tendency for the pCO₂ value to increase after NaHCO₃ ingestion after the second 200-m test

Fig. 3

a ∆pCO₂ for the 200-m test with water ingestion (∆pCO_2WATER) compared to that for the 200-m tests with NaHCO₃ ingestion (∆pCO_2NaHCO3) before each test. ∆pCO₂ was greater after the ingestion of NaHCO₃ during the 1-h recovery period. b ∆pCO₂ for the 200-m tests with water ingestion (∆pCO_2WATER) compared to that for the 200-m tests with NaHCO₃ ingestion (∆pCO_2NaHCO3) during the first minute of recovery after each test. ∆pCO₂ was greater after the previous NaHCO₃ ingestion during the 1-h recovery period, likely because of the inability to increase ventilation during swimming, which could compensate for the “excess” CO₂