Dose of Bicarbonate to Maintain Plasma pH During Maximal Ergometer Rowing and Consequence for Plasma Volume

Abstract

Rowing performance may be enhanced by attenuated metabolic acidosis following bicarbonate (BIC) supplementation. This study evaluated the dose of BIC needed to eliminate the decrease in plasma pH during maximal ergometer rowing and assessed the consequence for change in plasma volume. Six oarsmen performed "2,000-m" maximal ergometer rowing trials with BIC (1 M; 100-325 ml) and control (CON; the same volume of isotonic saline). During CON, pH decreased from 7.42 ± 0.01 to 7.17 ± 0.04 (mean and SD; p < 0.05), while during BIC, pH was maintained until the sixth minute where it dropped to 7.32 ± 0.08 and was thus higher than during CON (p < 0.05). The buffering effect of BIC on metabolic acidosis was dose dependent and 300-325 mmol required to maintain plasma pH. Compared to CON, BIC increased plasma sodium by 4 mmol/L, bicarbonate was maintained, and lactate increased to 25 ± 7 vs. 18 ± 3 mmol/L (p < 0.05). Plasma volume was estimated to decrease by 24 ± 4% in CON, while with BIC the estimate was by only 7 ± 6% (p < 0.05) and yet BIC had no significant effect on performance [median 6 min 27 s (range 6 min 09 s to 6 min 57 s) vs. 6 min 33 s (6 min 14 s to 6 min 55 s)]. Bicarbonate administration attenuates acidosis during maximal rowing in a dose-dependent manner and the reduction in plasma volume is attenuated with little consequence for performance.

Keywords: acidosis; bicarbonate supplementation; bohr effect; desaturation; hypoxaemia; plasma volume; rowing.

FIGURE 1

pH effect of different doses of bicarbonate administered intravenosly during maximal ergometer rowing in seven oarsmen. X-axis is the dose group of bicarbonate used (100: use of 100 mmol in two subjects, 200 use of 200–240 mmol in four subjects and 300 administration of 300–340 mmol in four subjects) while “0” represent the control saline trial in six subjects. Y-axis is the difference between the pH at rest in samples obtained in the sixth minute of rowing. It is a limitation not all subjects received same amount of bicarbonate.

FIGURE 2

Estimated rowing induced decrease in plasma volume (%) in trials with administration of bicarbonate (square) compared to control (circle). †, difference between rowing with bicarbonate and control; p < 0.05.