Instructions for use Title Relationship between Blood Lactate Concentration and Excessive CO 2 Expiration During and afterRamp Exercise

YUNOKI, T., OGATA, H. and YANO, T., Relationship between Blood Lactate Concentration and Excessive C02 Expiration During and after Ramp Exercise. Adv. Exerc. Sports Physiol., Vo1.9, No.3 pp.97 -103, 2003. The purpose of this study was to examine the kinetics of excessively expired COz and the blood lactate concentration ([La -D 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 (RIO), 20 W/min (R20) and 40 W/min (R40). Excessive COz expiration during exercise (COz excess) significantly correlated with the [La-] increase during exercise (Ll[La-D. Excessive COz expiration during recovery (post COz excess) significantly correlated with the [La -] increase during recovery (post Ll [La -D. However, COz excess in R40 was significantly lower compared with R20 and RIO, despite there being no significant difference in Ll [La -] among the three tests. In addition, post COz excess showed a positive value even when post Ll [La-] was zero. Endtidal COz pressure (PETCOz) decreased from the onset of respiratory compensation to about 10 min post-exercise in all tests. PETCOz decrement during exercise tended to be greater in RIO than in R40, and PETCOz decrement during post-exercise tended to be greater in R40 than in RIO. PETCOz was significantly related to [La -] during both at exhaustion and at 10 min post-exercise. However, PETCOz at the same [La-] was lower at 10 min post-exercise than at exhaustion. Furthennore, alactic O2 debt, which was calculated 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 which the blood lactate is not always the cause of excessive CO2 expiration in response to ramp exercise. The decrease in PET CO2 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.