Abstract
To examine the factors influencing the excess CO_2 output (CO_2 excess) during and after intensive exercise, seven healthy men performed 40 s intensive exercise on a cycle ergometer after ingestion of CaCO_3 (control condition) and NaHCO_3 (alkalosis condition). Increase of blood lactate concentration (⊿[La^-]) and decrease of blood bicarbonate concentration (⊿[HCO_3^-]) showed maximal values at 5 min postexercise in both conditions. There was no significant difference in the ⊿[La^-] between the two conditions, but the ⊿[HCO_3^-] was significantly higher in the alkalosis condition. There was no significant difference in the changes of main strong cations between the two conditions. In addition, although [HCO_3^-] decrease was significantly different between the two conditions, CO_2 excess was similar for the two conditions. Arterialized blood PCO_2 decreased below resting level during recovery in the control condition, but not in the alkalosis condition. These results suggest that the excess CO_2 output during and after intensive exercise is affected by the shift of strong anions including lactate into blood and the decrease in arterial PCO_2.
