The differences in CO2 kinetics during incremental exercise among sprinters, middle, and long distance runners

The purpose of this study was to investigate the differences in kinetics of CO2 output (VCO2) during incremental exercise in sprinters (S), middle (MD), and long distance runners (LD). In the steady state exercise, the VCO2 was linearly related to the O2 uptake (VO2). In the incremental exercise below anaerobic threshold (AT), the VCO2 was also linearly related to the VO2. The difference between the VCO2 estimates from the regression lines obtained in steady state and incremental exercise was added from the start of exercise up to a given time. The added values were defined as CO2 stores. The CO2 stores per body weight were significantly related to mixed venous CO2 pressure (PVCO2) determined by the CO2 rebreathing method. The slopes of the regression lines between PVCO2 and CO2 stores per body weight were not different among three groups. If VCO2 above AT is estimated from the VO2 using the regression line obtained in incremental exercise below AT, the estimated VCO2 is lower than the measured VCO2. The sum of the differences in VCO2 up to a given time was defined as CO2 excess. The CO2 excess per body weight was significantly related to delta LA (the difference between blood lactates at 5 min after exercise and at rest). The ratios of CO2 excess per body weight to delta LA were 3.30 +/- 1.49, 4.16 +/- 2.33, and 5.55 +/- 2.05 for sprinters, middle, and long distance runners, respectively. This ratio obtained in sprinters was significantly lower than that in long distance runners (p less than 0.01).