〈Originals〉Relationship between Blood Lactate Concentration and Excessive CO_2 Expiration During and after Ramp Exercise

摘要

YUNOKI, T., OGATA, H. and YANO, T., Relationship between Blood Lactate Concentration and Excessive CO_2 Expiration During and after Ramp Exercise. Abv. Exerc. Sports Physiol., Vol.9, No.3 pp.97-103, 2003. The purpose of this study was to examine the kinetics of excessively expired CO2 and the blood lactate concentration ([La-]) during and after ramp exercise. Six healthy males performed three different ramp exercise tests in which the work rate was increased as a ramp function at 10 W/min (R10), 20 W/min (R20) and 40 W/min (R40). Excessive CO2 expiration during exercise (CO2 excess) significantly correlated with the [La-] increase during exercise (△[La-]). Excessive CO2 expiration during recovery (post CO2 excess) significantly correlated with the [La-] increase during recovery (post △[La-]). However, Co2 excess in R40 was significantly lower compared with R20 and R10, despite there being no significant difference in △[La-] among the three tests, In addition, post CO2 excess showed a positive value even when post △[La-] was zero. Endtidal CO2 pressure (PETCO2) decreased from the onset of respiratory compensation to about 10 min post-exercise in all tests. PETCO2 decrement during exercise tended to be greater in R10 than in R40, and PETCO2 decrement during post-exercise tended to be greater in R40 than in R10. OETCO2 was significantly related to [La-] during both at exhaustion and at 10 min post-exercise. However, PETCO2 at the same [La-] was lower at 10 min post-exercise than at exhaustion. Furthermore, alactic O2 debt, which was calulated from O2 uptake kinetics during recovery, was significantly higher in R40 than in the other tests. These results suggest that there is a case in whichi the blood lactate is not always the couse of excessive CO2 expriration in response to ramp exercise. The decrease in PETCO2 and the H+ uptake-release by breakdown-resynthesis of phosphocreatine were thought to be main factors influencing the excessive CO2 expiration as well as the [La-} increase.