Effects of Sodium Bicarbonate on VO2 Kinetics During Heavy Exercise

Fred W. Kolkhorst; Robert S. Rezende; Susan S. Levy; Michael J. Buono


Med Sci Sports Exerc. 2004;36(11) 

In This Article


Arterialized blood pH before exercise in the bicarbonate trial was higher than before the control trial (7.512 ± 0.009 vs 7.425 ± 0.007, respectively; P = 0.001) ( Table 1 ). Most subjects experienced gastrointestinal distress (i.e., diarrhea) from the sodium bicarbonate ingestion, but there were no instances of vomiting. Average power output during the cycling trials was 208 ± 12 W.

There were no differences in O2 at the start ( O2base) or end of exercise ( O2 6); thus, bicarbonate ingestion did not affect the total amplitude of O2 during the 6-min bouts. Moreover, sodium bicarbonate did not affect O2 kinetics during the cardiodynamic phase (Table 2). During the rapid component, however, sodium bicarbonate ingestion slowed τ2 (P = 0.017). Time constants for the rapid component were 27.9 ± 3.5 and 20.8 ± 2.4 s for the bicarbonate and control trials, respectively. In spite of the faster kinetics during the rapid phase, though, MRT did not differ between trials.

Bicarbonate ingestion also affected the slow component, as A'3 was smaller during the bicarbonate trial (P = 0.040). A'3 for the bicarbonate and control trials were 463 ± 43 and 649 ± 53 mL·min-1, respectively. In addition, there were close to significant trends for a longer TD3 (P = 0.083) and faster τ3 in the bicarbonate trials (P = 0.105). Likewise, the smaller Δ O2 6–3 during the bicarbonate trial was also nonsignificant (P = 0.095).