Effects of sodium bicarbonate ingestion on EMG, effort sense and ventilatory response during intense exercise and subsequent active recovery

To determine whether post-exercise ventilation is related to decrease in blood pH and also whether post-exercise ventilation, associated or not with decreased blood pH, involves an increase in central motor command during exercise, we examined the effects of NaHCO(3) ingestion on the ventilatory response (VE), integrated electromyogram (iEMG) and effort sense of legs (ESL) during intense exercise (IE) and subsequent active recovery. Subjects performed two IE tests (105-110% of maximal work rate, 2 min) after ingestion of NaHCO(3) or CaCO(3). Subjects performed light load exercise (20 W) before and after IE for 6 min and 30 min, respectively. Although there was a significant difference in blood pH between the two conditions during and after IE, VE, iEMG and ESL were similar. iEMG returned to the pre-IE level immediately after the end of IE, while ESL showed slow recovery. VE decreased rapidly until about 50 s after the end of IE (fast phase) and then showed a slow recovery kinetics (slow phase). The ventilatory responses during the fast phase and during the slow phase were correlated with ESL at the end of IE and from 3 min after the end of IE, respectively. Moreover, there was no significant difference in the slopes and intercepts of regression lines between VE and ESL under the two conditions in both phases. These results suggest that the ventilatory response after IE is associated with effort sense indirectly-elicited by central motor command, but the effort sense-mediated response is not affected by blood pH.